Degradation of nitrobenzene using titania photocatalyst

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超声作用下含钛矿渣催化降解含硝基苯废水

硅酸盐学报 · 536 · 2009年超声作用下含钛矿渣催化降解含硝基苯废水康艳红，薛向欣，杨合，刘娇(东北大学，硼资源生态化综合利用技术与硼材料辽宁省重点实验室，沈阳 110004)摘要：以含钛矿渣为催化剂，用超声法对含硝基苯(nitrobenzene ，NB)废水进行了降解，用高效液相色谱仪对降解产物进行了分析。

结果表明：超声(ultrasound ，US)条件下含钛矿渣可以催化降解NB ；当超声频率为45 kHz ，高钛渣加入量为18.0 g/L 时，140 min 后NB 降解率达到100%；在超声产生的自由基作用下，NB 降解产物为二氧化碳和水，没有其它副产物产生；单独超声条件下，NB 的降解符合一级反应速率方程，表观速率常数k US =0.004 07/min ；超声催化条件下，NB 降解速率方程符合US sec p d[NB][NB][NB]d k k k t t−=+(其中：k sec 为NB 在催化剂表面降解的二级速率常数，k p 为与催化剂用量有关的常数)。

关键词：超声；含钛矿渣；硝基苯；降解；动力学中图分类号：TQ170.9 文献标志码：A 文章编号：0454–5648(2009)04–0536–07DEGRADATION OF NITROBENZENE IN WASTEWATER BY SLAG CONTAININGTITANIA WITH ULTRASOUNDKANG Yanhong ，XUE Xiangxin ，YANG He ，LIU Jiao(Liaoning Key Laboratory for Ecologically Comprehensive Utilization of Boron Resources ＆ Materials,Northeastern University, Shenyang 110004, China)Abstract: The removal efficiency of nitrobenzene (NB) catalyzed by slag containing titania under ultrasound (US) was investigated, and the products were also analyzed by high performance liquid chromatography. The results show that slag containing titania can remove NB catalytically in the presence of US. When 18.0 g/L high titania slag is used as catalyzer, the removal efficiency of NB can reach 100% after 140 min under 45 kHz ultrasonic frequency. NB is ultimately oxidized into CO 2 and H 2O without other by-products by the action of free radicals provided by the ultrasound-catalysis. The reaction factor of NB degradation by ultrasound action is first-order. The observed rate constant k US is 0.004 07/min. The corresponding reaction equation by US in the presence of high titania slag is US sec p d[NB][NB][NB]d k k k t t−=+(k sec is the second-order reaction rate of NB under US; k p is a constant corresponding to the amount of catalyst).Key words: ultrasound; slag containing titania; nitrobenzene; degradation; kinetics先进氧化技术的最新发展已将超声气穴纳入其中。

英文塑料

BIODEGEADABLE PLASTICS
The direction of the development of biodegradable plastics is using cellulose, starch, and other chitin polymer materials preparation of biodegradable plastics, further develop and improve the function and technology of natural polymer. Synthesis of biodegradable plastics by polymer design and fine synthesis.Through of biodegradable synthetic polymer biodegradation mechanism analysis, preparation of biodegradable plastics
APPLICATION
The use of degradable plastics are mainly in two areas: first, the application of ordinary plastic. In these areas, the application or consumption of plastic products is difficult to collect the damage to environment, such as agricultural plastic film and plastic packaging; second,is the field of plastic instead of other materials. In these areas the use of biodegradable plastics can bring convenience, such as golf course with a ball, a tropical rain forest afforestation seedlings with fixed material.

响应面法优化Fenton预处理精细化工废水

类、不饱和醛类和芳香类化合物. 研究显示ꎬＦｅｎｔｏｎ预处理能有效降解废水中难降解有机物ꎬ但出水仍未达到后续生化处理要求ꎬ
还需进一步优化或与其他预处理工艺组合.
关键词: Ｆｅｎｔｏｎ氧化法ꎻ 精细化工废水ꎻ 响应面ꎻ 反应动力学ꎻ 光谱分析
中图分类号: Ｘ７０３文章编号: １００１￣６９２９(２０１９)０８￣１４１９￣０８
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蜜环菌Am-07-22发酵对玉米赤霉烯酮降解效果影响及机理初探

王泽贤，赵宇楠，贾丹丹，等. 蜜环菌Am-07-22发酵对玉米赤霉烯酮降解效果影响及机理初探[J]. 食品工业科技，2024，45（1）：162−169. doi: 10.13386/j.issn1002-0306.2023030070WANG Zexian, ZHAO Yunan, JIA Dandan, et al. Effect and Mechanism of Armillaria mellea 07-22 Fermentation on the Degradation of Zearalenone[J]. Science and Technology of Food Industry, 2024, 45(1): 162−169. (in Chinese with English abstract). doi:10.13386/j.issn1002-0306.2023030070· 生物工程 ·蜜环菌Am-07-22发酵对玉米赤霉烯酮降解效果影响及机理初探王泽贤，赵宇楠，贾丹丹，纪晚唐，许　丁，向杨玲，蔡　丹*，刘景圣*（吉林农业大学食品科学与工程学院，小麦和玉米深加工国家工程研究中心，吉林长春 130118）摘　要：本研究以蜜环菌Am-07-22为试验菌株，采用真菌生物发酵的方式降解玉米赤霉烯酮（ZEN ），对蜜环菌降解ZEN 的降解效果进行研究，包括菌株对不同浓度ZEN 的降解效果以及不同培养时间、培养温度、初始pH 和接种量对菌株降解ZEN 的影响。

然后对降解机理进行初探，分析了菌丝体、发酵上清液、细胞内容物对ZEN 的降解作用，并研究了不同发酵时间、pH 、金属离子对发酵上清液降解ZEN 的影响，以及降解效果与菌株产漆酶活力的相关性分析。

结果表明：蜜环菌Am-07-22对ZEN 的降解效果良好，当ZEN 浓度为5 μg/mL 时，最适降解条件为培养时间8 d ，培养温度27 ℃，初始pH7.0，接种量10%，此时对ZEN 的降解率为78.72%。

磷酸银碘化银

Article /JPCC
ห้องสมุดไป่ตู้
High-Eﬃciency Visible-Light-Driven Ag3PO4/AgI Photocatalysts: Z‑Scheme Photocatalytic Mechanism for Their Enhanced Photocatalytic Activity
Zhihong Chen, Weilin Wang, Zhengguo Zhang, and Xiaoming Fang*
Key Laboratory of Enhanced Heat Transfer and Energy Conservation, the Ministry of Education, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, China ABSTRACT: High-eﬃciency visible-light-driven Ag3PO4/AgI photocatalysts with diﬀerent mole fractions of AgI have been synthesized via an in-situ anion-exchange method and characterized by X-ray diﬀraction (XRD), scanning electron microscopy (SEM), energydispersive spectroscopy (EDS), and UV−vis diﬀuse reﬂectance spectroscopy (DRS). Under visible light (>420 nm), the Ag3PO4/AgI photocatalysts exhibit enhanced photocatalytic activity compared to pure Ag3PO4 or AgI for the degradation of methyl orange and phenol, and the highest activity is reached by the Ag3PO4/AgI hybrid photocatalyst with 20% of AgI. The quenching eﬀects of diﬀerent scavengers suggest that the reactive h+ and O2•− play the major role in the MO degradation. Detailed X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) analysis reveals that Ag nanoparticles (NPs) form on the surface of Ag3PO4/AgI in the early stage of the photocatalytic oxidation process, thus leading to the transformation from Ag3PO4/ AgI to Ag3PO4/AgI@Ag. The excellent photocatalytic activity of the Ag3PO4/AgI photocatalysts can be ascribed to the eﬃcient separation of photogenerated electron−hole pairs through a Z-scheme system composed of Ag3PO4, Ag, and AgI, in which the Ag nanoparticles acted as the charge transmission bridge. The Ag3PO4/AgI hybrid remains good photocatalytic activity after ﬁve cycling runs.

The Abundance of Interstellar Nitrogen

a rXiv:as tr o-ph/971162v115Oct1997The Abundance of Interstellar Nitrogen 1David M.Meyer Department of Physics and Astronomy,Northwestern University,Evanston,IL 60208and Jason A.Cardelli 2and Ulysses J.Soﬁa Department of Astronomy and Astrophysics,Villanova University,Villanova,PA 19085ReceivedABSTRACTUsing the HST Goddard High Resolution Spectrograph(GHRS),we have obtained high S/N echelle observations of the weak interstellar N Iλλ1160,1161 absorption doublet toward the starsγCas,λOri,ιOri,κOri,δSco andκSco.In combination with a previous GHRS measurement of N I towardζOph,these new observations yield a mean interstellar gas-phase nitrogen abundance(per106H atoms)of106N/H=75±4(±1σ).There are no statistically signiﬁcant variations in the measured N abundances from sightline to sightline and no evidence of density-dependent nitrogen depletion from the gas phase.Since N is not expected to be depleted much into dust grains in these diﬀuse sightlines,its gas-phase abundance should reﬂect the total interstellar abundance.Consequently,the GHRS observations imply that the abundance of interstellar nitrogen(gas plus grains)in the local Milky Way is about80%of the solar system value of106N/H=93±16.Although this interstellar abundance deﬁcit is somewhat less than that recently found for oxygen and krypton with GHRS,the solar N abundance and the N I oscillator strengths are too uncertain to deﬁnitively rule out either a solar ISM N abundance or a2/3solar ISM N abundance similar to that of O and Kr.Subject headings:ISM:abundances—ISM:atoms1.IntroductionAccurate measurements of the elemental abundances in the interstellar medium are crucial to studies ranging from the chemical evolution of the Galaxy(Timmes,Woosley, &Weaver1995)to the composition of interstellar dust grains(Snow&Witt1996).Since it is diﬃcult to obtain such data,the traditional approach has been to adopt the solar system values as“cosmic”current-epoch abundance standards.Recently,sensitive UV measurements of very weak interstellar absorption lines with the Goddard High Resolution Spectrograph(GHRS)onboard the Hubble Space Telescope(HST)have begun to seriously challenge these solar standards.In particular,based on GHRS observations of the O Iλ1356absorption in13sightlines,Meyer,Jura,&Cardelli(1998)have measured a total (gas plus dust)abundance of interstellar oxygen that is2/3of the solar value.Cardelli& Meyer(1997)have found similar results for interstellar krypton which is important since Kr,as a noble gas,should not be depleted much into dust grains.Theseﬁndings are also consistent with the subsolar CNO abundances that have been measured in nearby B stars and are likely reﬂective of the current ISM abundance pattern(Gies&Lambert1992,Kilian 1992,Cunha&Lambert1994,Kilian,Montenbruck,&Nissen1994).Since the solar system abundances are presumably representative of the ISM at the time of the Sun’s formation 4.6Gyr ago and the ISM abundances should slowly increase over time(Audouze&Tinsley 1976,Timmes et al.1995),a2/3solar standard for the local ISM today is diﬃcult to understand in the context of Galactic chemical evolution models.Among the abundant CNO elements,nitrogen can potentially provide the best test of a subsolar ISM abundance pattern since it is the least likely to be signiﬁcantly depleted into dust grains.For example,using the wavenumber-integrated cross-section of the2.96µm N–H stretch(Tielens et al.1991),the ISO spectrum of the star VI Cyg No.12(Whittet et al.1997)limits the solid-state N abundance in the N–H stretch to106N/H<1in thisheavily reddened sightline.Copernicus observations(Ferlet1981,York et al.1983,Keenan, Hibbert,&Dufton1985)of various N I transitions in the ultraviolet have yielded a mean interstellar gas-phase N abundance that is50%to80%of the solar value(106N/H=93±16)(Grevesse&Noels1993).However,the scatter in these data is too great to discriminate the0.2dex diﬀerence between a solar and a B-star nitrogen abundance.Since this scatter is at least partially due to the errors in measuring the weakest and most optically thin N I lines,the greater sensitivity of GHRS makes it possible to establish a more accurate set of interstellar nitrogen abundances.In this Letter,we present the results of such an eﬀort involving new GHRS observations of the very weak N I intersystem doublet at1159.817 and1160.937˚A toward six stars.2.ObservationsObservations of the interstellar N Iλλ1160,1161absorption toward the starsγCas,λOri,ιOri,κOri,δSco,andκSco were obtained with GHRS in1996August and1997 January using the echelle-A grating and the2.′′0large science aperture.The observations of each star consist of multiple FP-Split exposures that are divided into four subexposures taken at slightly diﬀerent grating positions so as to minimize the impact of the GHRS Digicon detector’sﬁxed pattern noise(FPN)on the reduced data.Each subexposure was sampled twice per diode at a velocity resolution of3.5km s−1.The data were reduced using the Cardelli&Ebbets(1994)recipe to maximize theS/N ratio of GHRS spectra.In brief,this process involves:(1)merging the FP-Split subexposures in diode space so as to create a template of the FPN spectrum,(2)dividing each subexposure by this FPN spectrum,(3)aligning the rectiﬁed subexposures in wavelength space using the interstellar lines as a guide,and(4)summing the aligned subexposures to produce the net N I spectrum of each star.As illustrated in Figure1,theresulting continuum-ﬂattened spectra reveal convincing detections of the interstellar N I λ1160absorption in all of the six sightlines comprising our sample.The S/N ratios of these spectra range from150to250.Our measured equivalent widths for the N Iλ1160and λ1161lines are listed in Table1along with the previously reported GHRS measurements towardζOph(Savage,Cardelli,&Soﬁa1992).The N I column densities given in Table1were calculated using the Hibbert,Dufton, &Keenan(1985)oscillator strengths.The uncertainties in these theoretically-determined f-values should be no more than the quoted20%(Hibbert et al.1985)since Soﬁa,Cardelli, &Savage(1994)have empirically veriﬁed that they are consistent with the accuratef-values appropriate for the stronger N Iλ1200transitions.Theλλ1160,1161absorption is generally weak enough for N(N I)to be conﬁdently derived under the assumption that the lines are optically thin.However,based on the relative N I line strengths towardλOri andδSco,a slight correction for saturation was applied using a Gaussian curve-of-growthwith respective b-values of5.0+∞−2.5and10.0+∞−5.0km s−1.The resultant N I column densitiesare5%and6%greater than their weak line limits,respectively.The N I column density uncertainties given in Table1reﬂect the estimated errors in the measured equivalent widths and the saturation corrections(where applied).3.DiscussionWith an ionization potential of14.534eV,N I should be the dominant ion of N in H I regions,and little N I should originate from H II regions.Consequently,the ratio of N(N I)to the total H column density[N(H)=2N(H2)+N(H I)]should accurately reﬂect the interstellar gas-phase N/H abundance ratio.The values of N(H)listed in Table1were calculated from the H2column densities measured by Savage et al.(1977)(and Jenkins, Savage,&Spitzer1986forκSco)and the weighted means of the Bohlin,Savage,&Drake(1978)(Jenkins et al.1986in the case ofκSco)and Diplas&Savage(1994)N(H I) data.The resulting N(N I)/N(H)ratios for the7GHRS sightlines yield a weighted mean (Bevington1969)interstellar gas-phase N abundance of106N/H=75±4(±1σ)that is about80%of the Grevesse&Noels(1993)solar abundance(106N/H=93±16).The spread in the GHRS nitrogen abundances is about±0.1dex with the most discrepant values being those ofδSco andκSco at1.6σabove and1.1σbelow the mean,respectively.It is worth noting that these two sightlines also have the most discrepant N(H I)measurements in our sample.In the top panel of Figure2,the interstellar gas-phase N abundances are plotted as a function of the fractional abundance of molecular hydrogen,f(H2)=2N(H2)/N(H),in the GHRS sightlines.As discussed by Cardelli(1994),this parameter separates sightlines rather distinctly into groups with low and high f(H2)values that are indicative of the physical diﬀerences between UV transparent and H2self-shielding environments.Since the former type of environment is typically less hospitable to grains,higher gas-phase abundances of an element in the low f(H2)group than in the high group is a sign of both the presence of that element in dust and changes in the elemental dust abundance due to grain growth and/or destruction.Figure2clearly shows that the gas-phase abundance of interstellar N does not increase with decreasing f(H2)and is thus consistent with the expectation that nitrogen is not depleted much into dust grains.In the bottom panel of Figure2,the interstellar gas-phase N/Kr abundance ratio is plotted as a function of f(H2)for the four GHRS sightlines in common between this study and that of Cardelli&Meyer(1997).Krypton can be used as a hydrogen-like benchmark in interstellar abundance studies since it should not be depleted into grains and Kr/H exhibits a tight spread of±0.05dex among the ten sightlines studied by Cardelli&Meyer(1997). Although the N/Kr sample is too small for deﬁnitive conclusions,it does appear from Figure2that the spread in N/Kr is tighter than that in N/H.In particular,the sightline(δSco) that stands out the most with a solar abundance in terms of N/H drops back to the pack in terms of N/Kr.The most likely explanation for this behavior is an underestimate of the H column density towardδSco.Apart from this sightline,the spread in N/H is comparable to those found for Kr/H,O/H(Meyer et al.1998),and C/H(Cardelli et al.1996,Soﬁa et al.1997)with GHRS.In any case,theδSco discrepancy is small enough that omitting this sightline from the sample would only slightly reduce the weighted mean N abundance from 106N/H=75±4to73±5.The bottom line is that the GHRS measurements yield an interstellar nitrogen abundance that is about80%of the solar value with no statistically signiﬁcant variations from sightline to sightline.As discussed by Meyer et al.(1998),a subsolar abundance pattern in the local ISM today implies that something unusual happened to either the Sun or the local ISM in the context of standard Galactic chemical evolution models which predict that the ISM metallicity should slowly increase over time.The fact that the GHRS interstellar abundances of C,N,O,and Kr vary little from sightline to sightline makes it diﬃcult to understand this anomaly simply in terms of a typical ISM abundanceﬂuctuation.Possible explanations include the early enrichment of the solar system by a local supernova(Reeves 1978,Lee1979,Olive&Schramm1982),a recent infall of metal-poor gas in the local Milky Way(Comeron&Torra1994,Meyer et al.1994,Roy&Kunth1995),or an outward diﬀusion of the Sun from a birthplace at a smaller galactocentric distance(Wielen,Fuchs, &Dettbarn1996).A key prediction of the infall model is that the mixture of metal-poor gas with the local ISM would lower the abundances of all of the heavy elements below their solar values by a similar amount.The supernova enrichment hypothesis,on the other hand, would create uneven elemental overabundances in the Sun relative to the ISM that would reﬂect the nucleosynthetic yields of one or more supernova events.For example,the relative yield of O to N in Type II supernovae(Olive&Schramm1982)is appreciably greater thantheir relative present-day interstellar abundances.If the solar N abundance and the N Iλλ1160,1161oscillator strengths are accurate, the GHRS observations imply that nitrogen is somewhat more abundant in the ISM than the2/3solar values measured for oxygen and krypton(Meyer et al.1998,Cardelli&Meyer 1997).This N enhancement is illustrated in Figure2in terms of the N/Kr abundance ratio.Although it should be small,the presence of any N in grains can only serve to push this ratio(or N/O)further from the equal deﬁcit(with respect to the solar abundances)ﬁducial.Thus,it would appear that nitrogen presents a problem for the constant subsolar ISM abundance pattern predicted by the infall model.Furthermore,a higher value of N/O in the present-day ISM than in the Sun is what one might expect if the protosolar nebula was enriched by a local Type II supernova.However,these conclusions are not yet deﬁnitive because the solar abundances and the N Iλλ1160,1161f-values are still uncertain enough that neither a subsolar ISM N abundance similar to that of O and Kr or a solar ISM abundance can be ruled out.Indeed,the quality of the GHRS data is now high enough that the limitations in comparing the interstellar C,N,O,and Kr abundances no longer lie in the measurements themselves but in the accuracy of the weak line oscillator strengths and the solar abundances.Deﬁning an accurate set of ISM elemental abundances is also important in determining the composition of interstellar dust grains.Based on the B-star CNO abundances and the GHRS data on O and Kr in the ISM,a general consensus has been developing that a subsolar B-star standard may be the most appropriate for this work(Soﬁa et al.1994, Savage&Sembach1996,Snow&Witt1996).However,applying this standard to GHRS measurements of the interstellar gas-phase carbon abundance(Cardelli et al.1996,Soﬁa et al.1997)yields a C dust fraction(106C/H≈100)that is appreciably smaller than that typically required(106C/H≈300)by models to explain the total optical/UV dust opacity(Mathis&Whiﬀen1989,Siebenmorgan&Krugel1992,Kim,Martin,&Hendry1994). Mathis(1996)has recently developed a model that reduces this solid carbon requirement to106C/H≈150and other low-C models may soon follow.If N/O is indeed overabundant in the ISM with respect to the Sun,the same could also be true of C/O and thus somewhat relax the carbon constraints on these models.Such a C/O overabundance would be expected in the scenario where the early solar system is enriched by a nearby Type II supernova(Olive&Schramm1982).In any case,our GHRS observations of interstellar nitrogen allow for the possibility that at least some elements do not follow the same subsolar abundance pattern set for the ISM by O and Kr.This work was supported by STScI through a grant to Northwestern University.REFERENCESAnders,E.,&Grevesse,N.1989,Geochim.Cosmochim.Acta,53,197Audouze,J.,&Tinsley,B.M.1976,ARA&A,14,43Bevington,P.R.1969,Data Reduction and Error Analysis for the Physical Sciences(New York:McGraw-Hill),66Bohlin,R.C.,Savage,B.D.,&Drake,J.F.1978,ApJ,224,132Cardelli,J.A.1994,Science,265,209Cardelli,J.A.,&Ebbets,D.C.1994,in Calibrating Hubble Space Telescope,ed.J.C.Blades&S.J.Osmer(Baltimore:STScI),322Cardelli,J.A.,&Meyer,D.M.1997,ApJ,477,L57Cardelli,J.A.,Meyer,D.M.,Jura,M.,&Savage,B.D.1996,ApJ,467,334 Comeron,F.,&Torra,J.E.1994,A&A,281,35Cunha,K.,&Lambert,D.L.1994,ApJ,426,170Diplas,A.,&Savage,B.D.1994,ApJS,93,211Ferlet,R.1981,A&A,98,L1Gies,D.R.,&Lambert,D.L.1992,ApJ,387,673Grevesse,N.,&Noels,A.1993,in Origin and Evolution of the Elements,ed.N.Prantzos,E.Vangioni-Flam,&M.Casse(Cambridge:Cambridge Univ.Press),15 Hibbert,A.,Dufton,P.L.,&Keenan,F.P.1985,MNRAS,213,721Jenkins,E.B.,Savage,B.D.,&Spitzer,L.1986,ApJ,301,355Keenan,F.P.,Hibbert,A.,&Dufton,P.L.1985,Irish Astron.J.,17,20Kilian,J.1992,A&A,262,171Kilian,J.,Montenbruck,O.,&Nissen,P.E.1994,A&A,284,437Kim.S.H.,Martin,P.G.,&Hendry,P.D.1994,ApJ,422,164Lee,T.1979,Rev.Geophys.Space Phys.,17,1591Mathis,J.S.1996,ApJ,472,643Mathis,J.S.,&Whiﬀen,G.1989,ApJ,341,808Meyer,D.M.,Jura,M.,&Cardelli,J.A.1998,ApJ,493,in pressMeyer,D.M.,Jura,M.,Hawkins,I.,&Cardelli,J.A.1994,ApJ,437,L59Olive,K.A.,&Schramm,D.N.1982,ApJ,257,276Reeves,H.1978,in Protostars and Planets,ed.T.Gehrels(Tucson:Univ.Arizona Press), 399Roy,J.R.,&Kunth,D.1995,A&A,295,432Savage,B.D.,Bohlin,R.C.,Drake,J.F.,&Budich,W.1977,ApJ,216,291Savage,B.D.,Cardelli,J.A.,&Soﬁa,U.J.1992,ApJ,401,706Savage,B.D.,&Sembach,K.R.1996,ARA&A,34,279Siebenmorgan,R.,&Krugel,E.1992,A&A,259,614Snow,T.P.,&Witt,A.N.1996,ApJ,468,L65Soﬁa,U.J.,Cardelli,J.A.,Guerin,K.P.,&Meyer,D.M.1997,ApJ,482,L105Soﬁa,U.J.,Cardelli,J.A.,&Savage,B.D.1994,ApJ,430,650Tielens,A.G.G.M.,Tokunaga,A.T.,Geballe,T.R.,&Baas,F.1991,ApJ,381,181 Timmes,F.X.,Woosely,S.E.,&Weaver,T.A.1995,ApJS,98,617Whittet,D.C.B.,Boogert,A.C.A.,Gerakines,P.A.,Schutte,W.,Tielens,A.G.G.M., de Graauw,Th.,Prusti,T.,van Dishoeck,E.F.,Wesselius,P.R.,&Wright,C.M.1997,ApJ,in pressWielen,R.,Fuchs,B.,&Dettbarn,C.1996,A&A,314,438York,D.G.,Spitzer,L.,Bohlin,R.C.,Hill,J.,Jenkins,E.B.,Savage,B.D.,&Snow,T.P.1983,ApJ,266,L55Fig.1.—HST GHRS echelle spectra of the interstellar N Iλλ1159.817,1160.937absorption doublet towardδSco,λOri,κOri,κSco,γCas,andιOri at a velocity resolution of3.5 km s−1.The normalized spectra are displayed from top to bottom in order of decreasing total hydrogen column density in the observed sightlines.The measured S/N ratios of these spectra are all in the150-250range.The measured equivalent widths of the N I lines are listed in Table1.Fig. 2.—Interstellar nitrogen abundances measured with GHRS as a function of the logarithmic fraction of hydrogen in molecular form,f(H2)=2N(H2)/N(H),in the observed sightlines.In the top panel,the N abundances are plotted in terms of106N/H as taken from Table1.The short-dashed line among the data points represents the weighted mean interstellar gas-phase N abundance(per106H atoms)of106N/H=75±4.This N abundance is about80%of the Grevesse&Noels(1993)solar value(106N/H=93±16)represented by the long-dashed line.In the bottom panel,the N/Kr abundance ratio is plotted for the four sightlines in common between this paper and the Kr study of Cardelli& Meyer(1997).The short-dashed line among the data points represents the weighted mean interstellar gas-phase N/Kr abundance ratio of10−3N/Kr=82±5.The solar value of N/Kr(10−3N/Kr=55±13)represented by the long-dashed line incorporates the solar Kr abundance measured by Anders&Grevesse(1989).Table1.The GHRS Interstellar Nitrogen AbundancesStar N(H)a log f(H2)b Wλ(1160)c Wλ(1161)c N(N I)d106N/H e (cm−2)(m˚A)(m˚A)(cm−2)a N(H)=2N(H2)+N(H I)is the total hydrogen column density(±1σ)in the observed sightlines. These values reﬂect the H2column densities measured by Savage et al.1977(Jenkins,Savage,& Spitzer1986in the case ofκSco)and the weighted means of the Bohlin,Savage,&Drake1978 (Jenkins et al.1986in the case ofκSco)and Diplas&Savage1994N(H I)data.b f(H2)=2N(H2)/N(H)is the fractional abundance of hydrogen nuclei in H2in the observed sightlines.c The measured equivalent widths(±1σ)of the N I1159.817and1160.937˚A absorption lines.The value listed forλ1161towardιOri is a2σupper limit.d The derived N I column densities(±1σ)in the observed sightlines.TheζOph value is taken from the analysis of Savage,Cardelli,&Soﬁa1992.TheλOri andδSco values are corrected for a slightamount of saturation using respective Gaussian b-values(±1σ)of5.0+∞−2.5and10.0+∞−5.0km s−1.Theother sightlines are assumed to be optically thin in the N I transitions.e The abundance of interstellar gas-phase nitrogen(±1σ)per106H atoms in the observed sightlines. The uncertainties reﬂect the propagated N(H)and N(N I)errors.。

A New Equation of State for Carbon Dioxide Covering the Fluid Region

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3.3 3.4 3.5 3.6 3.7 3.8 4.
Melting Pressure. . . . . . . . . . . . . . . . . . . . . . .. Sublimation Pressure. . . . . . . . . . . . . . . . . . . .. Vapor Pressure ....................... " Saturated Liquid Density. . . . . . . . . . . . . . . .. Saturated Vapor Density. . . . . . . . . . . . . . . . .. Caloric Data on the Liquid-Vapor Phase Boundary. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Experimental Basis of the New Equation of State. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4.1 Thermal Properties .................... " 4.2 Specific Isobaric Heat Capacity. . . . . . . . . . .. 4.2.1 Experimental Results for the Specific Isobaric Heat Capacity. . . . . . . . . . . . .. 4.2.2 Results for the Specific Isobaric Heat

Degradation of vitamin C in citrus juice concentrates during storage

Degradation of vitamin C in citrus juice concentrates during storageHande Selen Burdurlu,Nuray Koca,Feryal Karadeniz*Ankara University,Faculty of Engineering,Food Engineering Department,Campus of Agricultural Faculty,Dis ßkapı06110Ankara,TurkeyReceived 16July 2004;accepted 7March 2005Available online 11May 2005AbstractKinetics of ascorbic acid degradation in citrus juice concentrates (orange,lemon,grapefruit,tangerine)during an eight week stor-age at 28,37and 45°C were investigated.The loss of ascorbic acid at each temperature followed a ﬁrst-order kinetic model.Acti-vation energy was determined in the range of 12.77±0.97–25.39±1.98kcal mol À1.Ascorbic acid retention after storage at 28,37and 45°C was about 54.5–83.7%,23.6–27%and 15.1–20.0%,respectively.Since hydroxymethylfurfural (HMF)is one of the decom-position compounds of ascorbic acid degradation,its formation was also investigated.HMF accumulation ﬁtted to a zero-order kinetic model and activation energy ranged from 43.41±0.67to 80.02±0.07kcal mol À1.Signiﬁcant correlation was obtained between HMF accumulation and ascorbic acid loss at all storage temperatures in all citrus juice concentrates.Ó2005Elsevier Ltd.All rights reserved.Keywords:Citrus juice concentrates;Ascorbic acid;HMF;Kinetics;Storage1.IntroductionNutritional quality of food during storage has be-come increasingly important problem.The loss of some nutrients such as ascorbic acid (vitamin C)might be a critical factor for the shelf life of some products as citrus juice concentrates (Laing,Schlueter,&Labuza,1978)since vitamin C content of citrus juices undergoes destruction during storage (Johnson,Braddock,&Chen,1995;Lee &Nagy,1988a;Solomon,Svanberg,&Sahlstro ¨m,1995).Ascorbic acid (AA)is an important component of our nutrition and used as additive in many foods because of its antioxidant capacity.Thus,it increases quality and technological properties of food as well as nutritional value (Larisch,Groß,&Pischetsrieder,1998;Solomon et al.,1995).However,AA is an unstable compound and under less desirable conditions it decom-poses easily (Fennema,1977;Lee &Coates,1999).Degradation of AA proceeds both aerobic and anaero-bic pathways (Huelin,1953;Johnson et al.,1995)and depends upon many factors such as oxygen,heat,light (Robertson &Samaniego,1986),storage temperature and storage time (Fellers,1988;Gordon &Samaniego-Esguerra,1990).Oxidation of ascorbic acid occurs mainly during the processing of citrus juices (Huelin,1953),whereas,anaerobic degradation of AA mainly appears during storage (Johnson et al.,1995;Lee &Nagy,1988a;Solomon et al.,1995)which is especially observed in thermally preserved citrus juices.It was reported that several decomposition reactive products occur via the degradation of vitamin C (Eskin,1990;Huelin,Coggiola,Sidhu,&Kennett,1971)and these compounds may combine with amino acids,thus result in formation of brown pigments (Clegg,1964;Larisch et al.,1998).Hydoxymethylfurfural (HMF)is one of the decomposition products of ascorbic acid (Eskin,1990;Solomon et al.,1995)and suggested that a precur-sor of brown pigments.It is used to evaluate severity of heating applied to fruit juices during processing and taken into account for quality control (Lee &Nagy,1988b ).Other pathways of HMF accumulation are0260-8774/$-see front matter Ó2005Elsevier Ltd.All rights reserved.doi:10.1016/j.jfoodeng.2005.03.026*Corresponding author.Tel.:+903123170550x1716;fax:+903123178711.E-mail address:karadeni@.tr (F.Karadeniz)./locate/jfoodengJournal of Food Engineering 74(2006)211–216known as degradation of reducing sugars(Ibarz,Paga´n, &Garza,1999;Lee&Nagy,1988b)and Maillard reac-tion(Yaylayan,1990).Since ascorbic acid degradation cause browning which is the other problem of quality loss in citrus juices during storage(Nagy,Rouseﬀ,Fisher,&Lee,1992; Tatum,Philip,&Berry,1969),it is necessary to describe ascorbic acid degradation and investigate kinetics of AA loss in stored citrus juices.The objective of this study was to determine kinetics of both ascorbic acid degradation and HMF formation in citrus juice concentrates during storage.2.Materials and methods2.1.MaterialsOrange,lemon,grapefruit and tangerine juice con-centrates at61°,44.5°,59°and59.5°Bx,respectively, were obtained from one of fruit juice producers in Tur-key.All citrus juice concentrates in glass jars were stored in darkness at28,37and45°C for eight weeks.Ascorbic acid and HMF contents were determined every week and analyses were carried out on two replicates.2.2.Methods2.2.1.Determination of soluble solids content and pH valueThe soluble solids content of concentrates was deter-mined as°Bx using a refractometer(NOW,Nippon Optical Work Co.,LTD.,Tokyo).The pH of samples was determined with a pH meter(Consort P407,Schott Gerate,Belgium).2.2.2.Determination of ascorbic acidThe spectrophotometric method(Pepkowitz,1943; Robinson&Stotz,1945)for determination of ascorbic acid was performed by using Unicam UV–VIS(UV-2) spectrophotometer at a wavelength of500nm against xylene.The loss of ascorbic acid in citrus juice concen-trates was calculated by using the standard equation for aﬁrst-order reaction given below:ln C¼ln C0Àktwhere C,the concentration at time t;C0,the concentra-tion at time zero;k,theﬁrst-order rate constant;t,the storage time(week).2.2.3.Determination of HMFColorimetric method was used for determination of HMF.This method is based on measurement of red color appears from reaction between thiobarbituric acid (TBA)and HMF on spectrophotometer at550nm against water(Koch,1966).2.2.4.Statistical analysisCorrelation coeﬃcients between ascorbic acid degra-dation and HMF were performed by MINITAB (Version of Release,13)statistical computer progr-amme.3.Results and discussionInitial vitamin C contents of orange,lemon,grape-fruit and tangerine juice concentrates were232.9,225, 205.8and97.9mg/100g,respectively(Table1).After an eight week storage,ascorbic acid contents of those samples at28,37and45°C decreased to194.9, 122.8,144.0,65mg/100g;52.4,54.6,55.5,23.1mg/ 100g and39.3,45,31.4,14.8mg/100g,respectively. It was observed that ascorbic acid decreased with increasing temperature as expected and retention of vitamin C(%)in those samples at28,37and45°C was83.7,54.5,70,66.4;22.5,24.3,27,23.6and16.9, 20,15.3,15.1,respectively.At storage temperature of 28°C,the loss of vitamin C in orange juice concentrate was lowest compared to the loss of other concentrates. Moreover,half destruction time of vitamin C was found higher in orange juice concentrate among the other samples(Table2).Ascorbic acid retentions in all concentrates at37and45°C were found almost similar.When ascorbic acid retention of citrus juice concen-trates plotted to versus storage time,determination coef-ﬁcients of the curves found between0.8635and0.9702. However,the plot of change in logarithm of ascorbic acid retentions yielded higher determination coeﬃcients (Table2).So,the loss of ascorbic acid in citrus juice concentrates at all temperatures was described as a ﬁrst-order reaction.A representative graph for log per-cent retention of ascorbic acid in grapefruit juice con-centrates is shown in Fig.1.Theﬁrst order kinetic model for ascorbic acid degra-dation determined in this study is in agreement with the other studies(Huelin,1953;Johnson et al.,1995;John-son&Toledo,1975;Lathrop&Leung,1980;Lee& Coates,1999).On the other hand,there have been stud-ies reported that ascorbic acid destruction follows a zero-order(Laing et al.,1978)or second-order reaction (Robertson&Samaniego,1986).Lee and Coates(1999) is also reported that the loss of vitamin C known to fol-lowﬁrst order reaction for orange juice stored below 50°C.Temperature dependence of ascorbic acid degrada-tion was determined by using the Arrhenius equation: k¼k0ÁeÀE a=RTk=rate constant;k0=pre-exponential factor;E a=acti-vation energy(kcal molÀ1);R=gas constant(1.987 kcal molÀ1KÀ1);T=absolute temperature in K.212H.S.Burdurlu et al./Journal of Food Engineering74(2006)211–216Activation energies (Table 3)were calculated by using Arrhenius plots of ascorbic acid degradation in citrus juice concentrates given in Fig.2and found higher in orange (pH 3.20),tangerine (pH 3.23)and grapefruit (pH 2.56)juice concentrates than that of lemon (pH 1.82)juice concentrates (Table 3).Activation energies (E a )calculated for ascorbic acid degradation in citrus juice concentrates were related with those reported by Johnson et al.(1995)(30kcal mol À1in orange juice ser-um)and Laing et al.(1978)(14–17kcal mol À1in an intermediate moisture model system).Temperature quotient (Q 10)values were also calcu-lated for the temperature ranges of 28–37°C,28–45°C and 37–45°C (Table 3).According to these values,the least eﬀect of temperature rise on ascorbic acid degrada-tion was observed in lemon juice concentrate.However,it can be easily seen that the reaction occurred in orange juice concentrate was highly aﬀected by temperature in-crease except at the range of 37–45°C.HMF concentration of citrus juice concentrates is given in Table 4.As can be seen in Table 4,after an eight week storage,HMF contents of citrus juice con-centrates at 28°C were ranged from 3.01to 28.32mg/kg.The variation of HMF values at 37°C was between 521.52and 1141.99mg/kg,while those values for 45°C ranged from 1401.1to 3252.3mg/kg.The increase of HMF at 45°C was approximately 2.7times higher than that of at 37°C.When HMF values of citrus juice concentrates plotted to versus storage time the best ﬁt model for HMF accumulation was zero-order and the determination coeﬃcients in relation to this reaction were shown in Table 2.A representative graph for HMF formation in citrus juice concentrates is given in Fig.3.Table 2Times of half destruction of ascorbic acid and determination coeﬃcients for ascorbic acid degradation and HMF accumulation in citrus juice concentrates SpeciesTemperature °CTimes of half destruction and determinationcoeﬃcients of ﬁrst-order ascorbic acid degradation Determination coeﬃcients of zero-order HMF formation t 1/2(week)k ±SD R 2k ±SDR 2Orange2824.750.0276±0.01080.91070.2698±0.03400.919437 3.750.1850±0.01330.979380.728±25.00240.922545 2.720.2550±0.02870.9512333.40±34.97290.9207Lemon2810.340.0670±0.00590.9742 3.788±0.67340.951837 3.790.1830±0.00410.884976.057±27.90780.945145 3.350.2070±0.03300.9869181.940±21.39650.9848Grapefruit2814.740.0470±0.00670.9326 3.7012±0.59460.935937 4.250.1626±0.01970.9862151.35±38.52090.972445 2.860.2420±0.01840.9740438.75±41.16380.9744Tangerine2815.060.0460±0.00330.88770.3965±0.01770.952237 4.150.1670±0.01080.927464.368±12.81440.9618452.790.2480±0.02970.9790315.77±34.19460.9523SD:Standard deviation.Table 1Vitamin C degradation in citrus juice concentrates during storage (mg/100g)Variety Temperature (°C)Storage (week)012345678Orange28232.9242.1226.4218.5214.0210.0207.0189.9194.937232.9208.0196.6138.9121.5106.291.369.052.445232.9198.8153.495.272.956.339.338.439.3Lemon28225.0198.8188.8173.5166.9163.8148.1139.8122.837225.0188.3153.4118.880.473.4101.849.854.645225.0191.4152.9109.2112.780.465.950.645.0Grapefruit28205.8194.0184.4164.3160.0159.1155.0139.9144.037205.8180.0136.8119.9108.395.782.160.755.545205.8152.0115.890.971.244.141.936.731.4Tangerine2897.995.380.480.981.573.077.070.065.03797.988.768.660.355.034.138.538.423.14597.968.651.540.630.124.018.713.914.8H.S.Burdurlu et al./Journal of Food Engineering 74(2006)211–216213Signiﬁcant correlation (0.780–0.967)was obtained be-tween ascorbic acid loss and HMF formation (p <0.05)during storage of citrus juice concentrates.HMF forma-tion in citrus juice concentrates is mainly attributed to decomposition of ascorbic acid.In addition,sugar deg-radation might also be attributed to HMF content,since it is known that this reaction occurs in acidic media (Ibarz et al.,1999;Lee &Nagy,1988b ).However Mail-lard reaction,known as the other pathway for HMF accumulation,is thought to have a minor eﬀect on HMF accumulation since Maillard reaction was re-tarded by acidic systems (Daniel &Whistler,1985).Fig.4shows Arrhenius plots of HMF accumulation in citrus juice concentrates.Activation energies and Q 10values of HMF formation were calculated in citrus juice concentrates and given in Table 3.In citrus juice concentrates activation energies for HMF formation were obtained as in the range of 43.41±0.67–80.02±0.07kcal mol À1.High activation energies and Q 10values in orange and tangerine juice concentratesindicated that HMF formation was more temperature dependent than the other samples.The lowest E a value for HMF formation was obtained in lemon juice con-centrate.The lowest activation energies determined in lemon juice concentrates for ascorbic acid degradation and HMF accumulation is also remarkable since both reactions are favoured at low pH values even if at low temperatures.Kinetics of HMF formation was also investigated by other studies and reported that this reaction ﬁtted to a zero-order (Resnik &Chirife,1979),ﬁrst-order (Ibarz et al.,1999;Robertson &Samaniego,1986;Tosi,Ciappini,Re´,&Lucero,2002)and second-order (Shallenberger &Mattick,1983)kinetic models.Activa-tion energy for HMF accumulation in apple juice model solution was reported as 28–39.6kcal mol À1by Resnik and Chirife (1979)and in pear puree determined as 27.5kcal mol À1by Tosi et al.(2002).Table 3Activation energies (E a )and temperature quotient (Q 10)values for ascorbic acid degradation and HMF accumulation ReactionSpecies E a ±SD (kcal mol À1)Q 1028–37°C 28–45°C 37–45°C Ascorbic acid degradationOrange 25.16±4.298.14 3.68 1.50Lemon 12.77±0.97 3.05 1.95 1.17Grapefruit 18.37±1.08 3.98 2.63 1.63Tangerine 18.94±0.74 4.18 2.70 1.65HMF accumulationOrange 80.02±0.07560.1966.71 5.89Lemon 43.41±0.6727.939.82 2.97Grapefruit 53.52±1.0161.5016.73 3.77Tangerine74.76±1.15317.0051.486.46SD:Standard deviation.214H.S.Burdurlu et al./Journal of Food Engineering 74(2006)211–2164.ConclusionAscorbic acid in citrus juice concentrates decreased with increasing temperature.The loss of ascorbic acid in citrus juice concentrates at all storage temperatures was described as a ﬁrst-order reaction.Orange juice con-centrate had the lowest reaction rate at 28°C when com-pared to other samples.Since ascorbic acid decomposes easily in acid solutions,lemon juice concentrates (pH 1.82)showed the highest ascorbic acid destruction.On the other hand,HMF accumulation of citrus juice con-centrates increased depending on storage temperature.It was observed that the increase of HMF in citrus juice concentrates at 45°C was approximately 2.7times higher than that of at 37°C.High activation energies and Q 10values of HMF formation in orange and tanger-ine juice concentrates indicated that this reaction was more temperature dependent than the other concen-trates.The lowest activation energy determined in lemon juice concentrates for HMF accumulation is remarkable since the formation of HMF is favoured at low pH val-ues even if at low temperatures.ReferencesClegg,K.M.(1964).Non-enzymic browning of lemon juice.Journal ofthe Science of Food and Agricultural,15,878–885.Daniel,J.R.,&Whistler,R.L.(1985).Carbonhydrates.In O.R.Fennama (Ed.),Food chemistry (second ed.,pp.70–137).New York:Marcel Dekker.Eskin,N.A.M.(1990).Biochemistry of food processing:Browningreactions in foods.In Biochemistry of foods (second ed.,pp.240–295).London:Academic Press.Fellers,P.J.(1988).Shelf life and quality of freshly squeezed,unpasteurized,polyethylene-bottled citrus juice.Journal of Food Science,53(6),1699–1702.Fennema,O.(1977).Loss of vitamins in fresh and frozen foods.FoodTechnology,31(12),32–38.Gordon,L.R.,&Samaniego-Esguerra,M.C.(1990).Eﬀect of solublesolids and temperature on ascorbic acid degradation in lemon juice stored in glass bottles.Journal of Food Quality,13,361–374.Table 4HMF formation in citrus juice concentrates during storage (mg/kg)Variety Temperature (°C)Storage (week)012345678Orange28 1.13 1.13 1.13 1.51 1.88 2.63 2.64 2.64 3.0137 1.1310.5730.5890.25141.99270.39358.38493.58640.8645 1.1338.51152.19352.71655.961138.201449.001945.602727.00Lemon280.37 5.288.6812.8319.2525.3024.5029.0728.32370.3742.6786.10157.47233.76460.35423.33526.05534.36450.37112.91231.87393.50538.14889.721024.901190.001401.10Grapefruit28 2.64 4.908.3012.4616.9926.0526.0528.3228.3237 2.6445.31134.44229.98421.45608.00783.61994.331141.9945 2.64131.04336.85745.841158.601864.802355.702854.203252.30Tangerine280.370.37 1.13 1.51 2.26 2.64 2.79 2.79 3.39370.3710.9539.27101.58164.27294.93357.25460.34521.52450.3736.25161.25396.52681.261131.001604.202014.402348.20H.S.Burdurlu et al./Journal of Food Engineering 74(2006)211–216215Huelin, F. E.(1953).Studies on the anaerobic decomposition of ascorbic acid.Food Research,18,633–639.Huelin,F.E.,Coggiola,I.M.,Sidhu,G.S.,&Kennett,B.H.(1971).The anaerobic decomposition of ascorbic acid in the pH range of foods and in more acid solutions.Journal of the Science of Food and Agricultural,22,540–542.Ibarz,A.,Paga´n,J.,&Garza,S.(1999).Kinetic models for colour changes in pear puree during heating at relatively high tempera-tures.Journal of Food Engineering,39,415–422.Johnson,J.R.,Braddock,R.J.,&Chen,C.S.(1995).Kinetics of ascorbic acid loss and nonenzymatic browning in orange juice serum:Experimental rate constants.Journal of Food Science,60(3), 502–505.Johnson,R.L.,&Toledo,R.T.(1975).A research note:Storage stability of55°Brix orange juice concentrate aseptically packaged in plastic and glass containers.Journal of Food Science,40, 433–434.Koch,J.(1966).Die Beurteilung von Fruchtsaeften im Hinblick auf ihren HMF Gehalt.Deutsche Lebensmittel Rundschau,62,105–108. Laing,B.M.,Schlueter,D.L.,&Labuza,T.P.(1978).Degradation kinetics of ascorbic acid at high temperature and water activity.Journal of Food Science,43(5),1440–1443.Larisch,B.,Groß,U.,&Pischetsrieder,M.(1998).On the reaction of L-ascorbic acid with propylamine under various conditions:quan-tiﬁcation of the main products by HPLC/DAD.Zeitschrift fur Lebensmittel-Untersuchung Und-Forschung A,206,333–337. Lathrop,P.J.,&Leung,H.K.(1980).Rates of ascorbic acid degradation during thermal processing of canned peas.Journal of Food Science,45,152–153.Lee,H.S.,&Coates,G. A.(1999).Vitamin C in frozen,fresh squeezed,unpasteurized,polyethylene-bottled orange juice:A storage study.Food Chemistry,65,165–168.Lee,H.S.,&Nagy,S.(1988a).Quality changes and nonenzymatic browning intermediates in grapefruit juice during storage.Journal of Food Science,53(1),168–171.Lee,H.S.,&Nagy,S.(1988b).Relationship of sugar degradation to detrimental changes in citrus juice quality.Food Technology,11, 91–97.Nagy,S.,Rouseﬀ,R.L.,Fisher,J.F.,&Lee,H.S.(1992).HPLC separation and spectral characterization of browning pigments from white grapefruit juice stored in glass and cans.Journal of Agricultural and Food Chemistry,40,27–31.Pepkowitz,L.P.(1943).The rapid determination of ascorbic acid by the adaptation of StotzÕs method to plant materials.Journal of Biological Chemistry,151,405.Resnik,S.,&Chirife,J.(1979).Eﬀect of moisture content and temperature on some aspects of nonenzymatic browning in dehydrated apple.Journal of Food Science,44(2),601–605. Robertson,G.L.,&Samaniego,C.M.L.(1986).Eﬀect of initial dissolved oxygen levels on the degradation of ascorbic acid and the browning of lemon juice during storage.Journal of Food Science, 51(1),184–187.Robinson,W.B.,&Stotz,E.(1945).The indophenol-xylene extraction method for ascorbic acid and modiﬁcations for interfering substances.Journal of Biological Chemistry,160,217. Shallenberger,R.S.,&Mattick,L.R.(1983).Relative stability of glucose and fructose at diﬀerent acid pH.Food Chemistry,12, 159–165.Solomon,O.,Svanberg,U.,&Sahlstro¨m,A.(1995).Eﬀect of oxygen andﬂuorescent light on the quality of orange juice during storage at8°C.Food Chemistry,53,363–368.Tatum,J.H.,Philip, E.S.,&Berry,R. E.(1969).Degradation products from ascorbic acid.Journal of Agricultural and Food Chemistry,17(1),38–40.Tosi,E.,Ciappini,M.,Re´,E.,&Lucero,H.(2002).Honey thermal treatment eﬀects on hydroxymethlfurfural content.Food Chemis-try,77,71–74.Yaylayan,V.(1990).In search of alternative mechanisms for the Maillard reaction.Trends in Food Science and Technology,1(7), 20–22.216H.S.Burdurlu et al./Journal of Food Engineering74(2006)211–216。

USP 1087 固有溶出原文

1087 APPARENT INTRINSIC DISSOLUTION—DISSOLUTION TESTING PROCEDURES FOR ROTATING DISK ANDSTATIONARY DISKThis general information chapter Apparent Intrinsic Dissolution—Dissolution Testing Procedures for Rotating Disk and Stationary Disk 1087 discusses the determination of dissolution rates from nondisintegrating compacts exposing a fixed surface area to a given solvent medium. Compact, as used here, is a nondisintegrating mass resulting from compression of the material under test using appropriate pressure conditions. A single surface having specified physical dimensions is presented for dissolution. Determination of the rate of dissolution can be important during the course of the development of new chemical entities because it sometimes permits prediction of potential bioavailability problems and may also be useful to characterize compendial articles such as excipients or drug substances. Intrinsic dissolution studies are characterization studies and are not referenced in individual monographs. Information provided in this general information chapter is intended to be adapted via a specific protocol appropriate to a specified material.Dissolution rate generally is expressed as the mass of solute appearing in the dissolution medium per unit time (e.g., mass sec–1), but dissolution flux is expressed as the rate per unit area (e.g., mass cm–2 sec–1). Reporting dissolution flux is preferred because it is normalized for surface area, and for a pure drug substance is commonly called intrinsic dissolution rate. Dissolution rate is influenced by intrinsic solid-state properties such as crystalline state, including polymorphs and solvates, as well as degree of noncrystallinity. Numerous procedures are available for modifying the physicochemical properties of chemical entities so that their solubility and dissolution properties are enhanced. Among these are coprecipitates and the use of racemates and enantiomeric mixtures. The effect of impurities associated with a material can also significantly alter its dissolution properties. Dissolution properties are also influenced by extrinsic factors such as surface area, hydrodynamics, and dissolution medium properties, including solvent (typically water), presence of surfactants, temperature, fluid viscosity, pH, buffer type, and buffer strength.Rotating disk and stationary disk dissolution procedures are sufficiently versatile to allow the study of characteristics of compounds of pharmaceutical interest under a variety of test conditions. Characteristics common to both apparatuses include the following:1.They are adaptable to use with standard dissolution testing stations, and both use a tablet die to hold the nondisintegratingcompact during the dissolution test.2.They rely on compression of the test compound into a compact that does not flake or fall free during the dissolution test.3. A single surface of known geometry and physical dimension is presented for dissolution.4.The die is located at a fixed position in the vessel, which decreases the variation of hydrodynamic conditions.A difference between the two procedures is the source of fluid flow over the dissolving surface. In the case of the rotating disk procedure, fluid flow is generated by the rotation of the die in a quiescent fluid, but fluid flow is generated by a paddle or other stirring device for the stationary disk procedure.EXPERIMENTAL PROCEDUREThe procedure for carrying out dissolution studies with the two types of apparatus consists of preparing a nondisintegrating compact of material using a suitable compaction device, placing the compact and surrounding die assembly in a suitable dissolution medium, subjecting the compact to the desired hydrodynamics near the compact surface, and measuring the amount of dissolved solute as a function of time.Compacts are typically prepared using an apparatus that consists of a die, an upper punch, and a lower surface plate fabricated out of hardened steel or other material that allows the compression of material into a nondisintegrating compact. An alternative compaction apparatus consists of a die and two punches. Other configurations that achieve a nondisintegrating compact of constant surface area also may be used. The nondisintegrating compact typically has a diameter of 0.2 cm to 1.5 cm.Compact PreparationAttach the smooth lower surface plate to the underside of the die, or alternatively, insert the lower punch using an appropriate clamping system. Accurately weigh a quantity of material necessary to achieve an acceptable compact and transfer to the die cavity. Place the upper punch into the die cavity, and compress the powder on a hydraulic press at a compression pressure required to form a nondisintegrating compact that will remain in the die assembly for the length of the test. Compression for 1 minute at 15 MPa usually is sufficient for many organic crystalline compounds, but alternative compression conditions that avoid the formation of capillaries should be evaluated. For a given substance, the compact preparation, once optimized is standardized to facilitate comparison of different samples of the substance.Changes in crystalline form may occur during compression; therefore, confirmation of solid state form should be performed by powder X-ray diffraction or other similar technique. Remove the surface plate or lower punch. Remove loose powder from the surface of the compact and die by blowing compressed air or nitrogen over the surface.Dissolution MediumThe choice of dissolution medium is an important consideration. Whenever possible, testing should be performed under sink conditions to avoid artificially retarding the dissolution rate due to approach of solute saturation of the medium. Dissolutionmeasurements are typically made in aqueous media. To approximate in vivo conditions, measurements may be run in the physiological pH range at 37. The procedure when possible is carried out under the same conditions that are used to determine the intrinsic solubility of the solid state form being tested. Dissolution media should be deaerated immediately prior to use to avoid air bubbles forming on the compact or die surface.1The medium temperature and pH must be controlled, especially when dealing with ionizable compounds and salts. In the latter cases, the dissolution rate may depend strongly on the pH, buffer species, and buffer concentration. A simplifying assumption in constant surface area dissolution testing is that the pH at the surface of the dissolving compact is the same as the pH of the bulk dissolution medium. For nonionizable compounds, this is relatively simple because no significant pH dependence on dissolution rate is expected. For acids and bases, the solute can alter the pH at and near the surface of the compact as it dissolves. Under these conditions, the pH at the surface of the compact may be quite different from the bulk pH due to the self-buffering capacity of the solute. To assess intrinsic solubility, experimental conditions should be chosen to eliminate the effect of solute buffering, alteration of solution pH, and precipitation of other solid state forms at the surface of the compact. For weak acids, the pH of the dissolution medium should be one to two pH units below the pKa of the dissolving species. For weak bases, the pH of the dissolution medium should be one to two pH units above the pKa of the dissolving species.ApparatusRotating Disk— A typical apparatus (Figure 1) consists of a punch and die fabricated out of hardened steel. The base of the die has three threaded holes for the attachment of a surface plate made of polished steel, providing a mirror-smooth base for the compacted pellet. The die has a cavity into which is placed a measured amount of the material whose intrinsic dissolution rate is to be determined. The punch is then inserted in the die cavity and the test material is compressed with a hydraulic press. [NOTE—A hole through the head of the punch allows insertion of a metal rod to facilitate removal from the die after the test.] A compacted pellet of the material is formed in the cavity with a single face of defined area exposed on the bottom of the die.Figure 1The die assembly is then attached to a shaft constructed of an appropriate material (typically steel). The shaft holding the die assembly is positioned so that when the die assembly is lowered into the dissolution medium (Figure 2) the exposed surface of the compact will be not less than 1.0 cm from the bottom of the vessel and nominally in a horizontal position. The die assembly should be aligned to minimize wobble, and air bubbles should not be allowed to form on the compact or die surface.Figure 2A rotating disk speed of 300 rpm is recommended. Typical rotation speeds may range from 60 rpm to 500 rpm. The dissolution rate depends on the rotation speed used. This parameter should be selected in order to admit at least five sample points during the test, but excessive stirring speeds may create shear patterns on the surface of the dissolving material that could cause aberrant results (i.e., nonlinearity). Typically, the concentration of the test specimen is measured as a function of time, and the amount dissolved is then calculated. The sampling interval will be determined by the speed of the dissolution process. If samples are removed from the dissolution medium, the cumulative amount dissolved at each time point should be corrected for losses due to sampling.Stationary Disk— The apparatus (Figure 3) consists of a steel punch, die, and a base plate. The die base has three holes for the attachment of the base plate. The three fixed screws on the base plate are inserted through the three holes on the die and then fastened with three washers and nuts. The test material is placed into the die cavity. The punch is then inserted into the cavity and compressed, with the aid of a bench top press. The base plate is then disconnected from the die to expose a smooth compact pellet surface. A gasket is placed around the threaded shoulder of the die and a polypropylene cap is then screwed onto the threaded shoulder of the die.The die assembly is then positioned at the bottom of a specially designed dissolution vessel with a flat bottom (Figure 4). The stirring unit (e.g., paddle) is positioned at an appropriate distance (typically 2.54 cm) from the compact surface. The die assembly and stirring unit should be aligned to ensure consistent hydrodynamics, and air bubbles should not be present on the compact surface during testing. Alternative configurations may be utilized if adequate characterization and control of the hydrodynamics can be established.Figure 3Figure 4The dissolution rate depends on the rotation speed and precise hydrodynamics that exist. Typically, the concentration of the test specimen is measured as a function of time, and the amount dissolved is then calculated. The sampling interval will be determined by the speed of the dissolution process (see Rotating Disk). If samples are removed from the dissolution medium, the cumulative amount dissolved at each time point should be corrected for losses due to sampling.DATA ANALYSIS AND INTERPRETATIONThe dissolution rate is determined by plotting the cumulative amount of solute dissolved against time. Linear regression analysis is performed on data points in the initial linear region of the dissolution curve. The slope corresponds to the dissolution rate (mass sec–1). (More precise estimates of slope can be obtained using a generalized linear model that takes into account correlations among the measurements of the cumulative amounts dissolved at the various sampling times.)The amount versus time profiles may show curvature. When this occurs, only the initial linear portion of the profile is used todetermine the dissolution rate. Upward curvature (positive second derivative) of the concentration versus time data is typicallyindicative of a systematic experimental problem. Possible problems include physical degradation of the compact by cracking, delaminating, or disintegration. Downward (negative second derivative) curvature of the dissolution profile is often indicative of a transformation of the solid form of the compact at the surface or when saturation of the dissolution medium is inadvertently being approached. This often occurs when a less thermodynamically stable crystalline form converts to a more stable form. Examples include conversion from an amorphous form to a crystalline form or from an anhydrous form to a hydrate form, or the formation of a salt or a salt converting to the corresponding free acid or free base. If such curvature is observed, the crystalline form of the compact may be assessed by removing it from the medium and examining it by powder X-ray diffraction or another similar technique to determine if the exposed surface area is changing.The constant surface area dissolution rate is reported in units of mass sec –1, and the dissolution flux is reported in units of mass cm –2 sec –1. The dissolution flux is calculated by dividing the dissolution rate by the surface area of the compact. Test conditions, typically a description of the apparatus, rotation speed, temperature, buffer species and strength, pH, and ionic strength should also be reported with the analyses.1 One method of deaeration is as follows: Heat the medium, while stirring gently, to about 41, immediately filter under vacuum using a filter having a porosity of 0.45 µm or less, with vigorous stirring, and continue stirring under vacuum for about 5 minutes. Other deaeration techniques for removal of dissolved gases may be used.Auxiliary Information— Please check for your question in the FAQs before contacting USP.USP32–NF27 Page 549Pharmacopeial Forum : Volume No. 33(2) Page 269 Topic/QuestionContact Expert Committee General Chapter William E. BrownSenior Scientist1-301-816-8380(BPC05) Biopharmaceutics05。

Review and comparisons of DR models of equilibrium adsorption of binary mixtures of organic vapors

Carbon 40(2002)231–239Review and comparisons of D/R models of equilibrium adsorption of binary mixtures of organic vapors on activatedcarbons*G.O.Wood Los Alamos National Laboratory ,Mail Stop K -486,Los Alamos ,NM 87545,USAReceived 5November 2000;accepted 20February 2001AbstractPublished models and options for predicting equilibrium adsorption capacities of multicomponent mixtures using single component Dubinin/Radushkevich isotherm equations and parameters were reviewed.They were then tested for abilities to predict total and component capacities reported for 93binary adsorbed mixtures.The best model for calculating molar distributions was the Ideal Adsorbed Solution Theory (IAST),which balances spreading bined with the IAST,total and component capacities were best calculated using either the Lewis or original Bering equation with the Ideal Adsorbed Solution (Raoult’s Law)assumption.©2002Elsevier Science Ltd.All rights reserved.Keywords :A.Activated carbon;C.Adsorption,modelling;D.Phase equilibria1.Introductionequation [2]is the most versatile,proven,and useful model for predicting,as well as describing,equilibrium adsorp-The impetus for this review and testing of multicom-tion capacities of organic vapors on ordinary commercial ponent vapor adsorption models was to choose the best one activated carbons [1,3].For specialized carbons the more as a basis for developing a model of adsorption onto general Dubinin/Astakhov equation [4]with an additional activated carbon of vapors from mixtures in ﬂowing air.parameter can be used.These Dubinin equations have the One application goal is the prediction of service lives advantages of including:(a)carbon property parameters,(breakthrough times)of organic vapor air-purifying respir-(b)vapor property parameters,and (c)temperature.Only ator cartridges.In searching and reviewing the diverse and the Kisarov equation [5]can also claim this,but it has been scattered literature we recognized the need to summarize much less proven with data and was less successful in the proposed models and publish them together in one place.preliminary studies for mixtures [1].Other isotherm equa-Since they have been validated based on different and tions,particularly the Freundlich equation,are useful for limited data sets (often for light gases,not vapors of correlating experimental adsorption capacities,but have condensable chemicals),we also saw a need to compare had little success in predicting capacities for unmeasured models with a common set of multivapor data.vapors.The bases for multicomponent adsorption models are Therefore,only mixture models based on the Dubinin/always the adsorption isotherm equations and parameters Radushkevich (D/R)adsorption isotherm equation were of individual components.Many of the isotherm equations included in this review and study.The single vapor D/R proposed for describing adsorption isotherm data (Freun-equation for n moles adsorbed (e.g.mol/g)in equilibrium dlich,Langmuir,Langmuir/Freundlich,Dubinin/Radus-with its vapor pressure (or concentration in any consistent hkevich,Polanyi,Kisarov,Vacancy Solution Model,and units)p can be expressed as:Johns)have been reviewed for multicomponent applicabili-2W RTo2ty [1].The Dubinin/Radushkevich adsorption isotherm]]n 5exp 2ln(p /p )(1)hj o F S D Gsat b E V om3where W (cm /g)is the micropore volume of the ad-*Tel.:11-505-667-9824;fax:11-505-665-2192.o E -mail address :gerry@ (G.O.Wood).sorbent and E (kJ/mol)is its reference adsorption energy;o 0008-6223/02/$–see front matter ©2002Elsevier Science Ltd.All rights reserved.PII:S0008-6223(01)00090-2232G .O .Wood /Carbon 40(2002)231–239o 3V (cm /mol)is the liquid molar volume of the adsorbate,m p p 1p s12s1s2]]]]b is its afﬁnity coefﬁcient (relative to the reference),and 5(3)p p 1p 1212p is the vapor pressure of its unadsorbed bulk form at sat temperature T .One of the best features of the D/R The corresponding D/R equation for a multicomponent equation is the inclusion of the afﬁnity coefﬁcient,which mixture is:allows the application of the parameters of micropore 22W S p R T os i volume and reference adsorption energy measured with ]]]]]n 5exp2ln (4)S D F S S DD GT V b E S p one vapor to predict adsorption capacities of other vapors.mTT oiA thorough review with compilations and correlations of This equation will be called the Bering2model.They afﬁnity coefﬁcients has been published [6],which makes found that Eq.(4)well described ethyl chloride–diethyl single vapor isotherms easily predictable,even for water ether and diethyl ether–chloroform mixtures adsorbed on vapor.Benzene is usually chosen as the reference vapor an activated carbon.Phase diagrams of liquid mixtures (b 51.0).were used to get standard state pressures p of the s i components.Under certain conditions Eqs.(2)and (4)were shown to be equivalent [8].2.BackgroundAnother approach has been taken in weighting ad-sorption potentials.Xie et al.[9]used:2.1.Mixture D /R isotherm equationso´5S x ln(g x p /p )(5)T i i i sat i i The simplest extensions of the D/R equation to mixtures where g are activity coefﬁcients,which in their applica-i of miscible components involve mole fraction (x )weight-i tions for three binary mixtures (benzene–hexane,benzene–ing of afﬁnity coefﬁcient (b ),partial liquid molar volume i pentane,and hexane–pentane)on two carbons were appar-(V ),and adsorption potential (´5RT ln[p /p ])param-m i i s i i ently taken as unity.They did not use the D/R equation,eters of the components i to calculate total molar capacity,but a similar one with the same weighted terms and an n ,for the mixture.This was ﬁrst proposed by Bering et T additional empirical parameter for micropore size dis-al.[7]:tribution ing this weighting approach with the Bering1Eq.(2)gives:2W ´oT]]]n 5exp2(2)F S D GT V b E o 2mT T o2W S x ln (x p /p )RT oi i sat i i ]]]]]]]n 5exp2(6)F HJ GS D T V E b wheremToTTaking the standard reference component pressures to be x b 5S x b i T i i o p (superscript o indicates pure component)is the same sat i V 5S x V mT i m ias assuming Raoult’s Law and an ideal adsorbed solution ´5RT S x ln(p /p )Ti s i i (see later discussion).Therefore,Eq.(6)will be referred to as the Bering1–IAS model and option.This equation will be called the Bering1model.Mixture D/R isotherm equations such as Eqs.(2),(4)Bering et al.[7]left to ‘experience’which to choose for and (6)give only the total moles of mixture adsorbed.The the standard reference state of a mixture and the corre-component distributions (e.g.as moles n or mole fractions i sponding standard pressures p of components i in the s i x )must be known or determined independently by another i adsorbed mixture:‘...the state of a solution whose assumption and equation.composition is equal to the composition of the adsorbed phase or the state of a solution existing in equilibrium with 2.2.Lewis equationvapor whose composition is equal to the composition of the equilibrium vapor above the adsorption phase,....’The equation most often used to obtain moles of mixture They suggested that the partial molar volumes be de-components when total molar capacity is known or calcu-termined ‘from the phase diagram of the volume lated is:solution,....’Such selections of standard states and molar volumes are not practical for a widely applicable predictive n i ]S 51(7)o model for mixtures,since the required mixture phase n idiagrams usually do not exist.o Bering et al.[7]also proposed an alternative in which where n are the reference adsorbed molar capacities of the i the relative partial pressures of the components of the pure components and n are the molar capacities of the i mixture are set equal to the ratio of the sum of the components in the adsorbed mixture.It is based on an pressures of the components to the sum of the standard empirical correlation obtained for adsorption from constant state pressures.For a binary mixture this is:total pressure mixtures of hydrocarbon gases by Lewis etG .O .Wood /Carbon 40(2002)231–239233al.[10].The Lewis equation for a binary mixture in terms and the sum of mole fractions x in the adsorbate equal toi of mole fractions and total molar capacity (mol/g)is:unity to calculate the numbers of moles of each component adsorbed.However,this assumption of additivity is not a x x 112]]]necessary part of the Polanyi mixture theory.Mixture 51(8)o o n n n T 12isotherm equations,the Lewis equation,molar propor-tionality,or any other way of calculating or measuring Xie et al.[9]proposed a volumetric form of the Lewis total adsorbed molar capacity can be combined with the equation for non-ideal mixtures:mole fractions obtained from Eq.(10)to get molar V n m i icapacities of mixture components.]]S 51(9)o o V n m i i2.4.Ideal adsorbed solution theory (IAST )Partial molar volumes V for each mixture composition m i must be obtained from independent mixing data.The Myers and Prausnitz [15]are credited with the thermo-Lewis equation can also be used to calculate total molar dynamically consistent Ideal Adsorption Solution Theory,capacity when the mole fractions are determined by sometimes called the Myers–Prausnitz theory.They as-another method (see below).sumed Raoult’s Law and the concept of equality of Since the original Lewis correlation was obtained from spreading pressures P for each component:mixtures at constant total pressure,the reference adsorbedi o omolar capacities n should be calculated at p 5S p ,the i i j o p itotal pressure of the components,rather than at p .How-oi n RT iever,Lavanchy et al.[11]and Sundaram [12]both ]]P 5Ed p (12)i iA p isuccessfully applied the Lewis equation assuming Raoult’s 0o Law for an ideal solution for which p 5p /x .For these i i i o where n is the number of moles of pure component i in cases the proper D/R standard reference pressure is p 5i s i o the adsorbed phase obtained from a pure component p ,the saturation vapor pressure of the pure component i .sat i o isotherm for a vapor pressure p .The value of p is that i i corresponding to the spreading pressure.A is the speciﬁc 2.3.Polanyi adsorption potential theoryarea of the sorbent.Grant and Manes [14]stated that their adsorption theory for mixtures and the IAST are practically One of the most popular theories relating adsorption ofequivalent if the correlating divisor is molar volume.vapors of single pure chemicals is the Polanyi Theory [13].A major difﬁculty with the IAST model is the require-Lewis et al.[10]and Grant and Manes [14]have de-ment that the adsorption isotherms (actually,the n /p veloped it for mixtures.The latter assumed:(a)a liquid-i i ratios as functions of p )be accurately deﬁned to zero like adsorbate mixture in which the adsorption potential of i pressure and capacity,so that they can be integrated.Some each pure adsorbed component is determined by the total [1]have used Freundlich and other isotherm equations adsorbate volume of the mixture,(b)Raoult’s Law as the with this property or have ﬁt the lower coverage portion of relationship between the partial pressure of each com-experimental or theoretical isotherms with empirical equa-ponent and its adsorbate mole fraction,and (c)the adsor-tions that can be integrated analytically.Sundaram [12]bate volumes are additive.According to the Polanyi truncated a logarithmic expansion of the inverted D/R Eq.Theory all characteristic curves (adsorption capacities vs.(1)to get the Henry’s Law limit and apply the IAST.adsorption potentials)on a given adsorbent are superim-Alternately,Grant and Manes [14]pointed out that the posable to form a single curve by using correlating divisors integration difﬁculties for the IAST could be overcome by for the adsorption potentials.This correlating divisor can using any Polanyi-type correlation.Subsequently,Lavan-be (a)molar volume calculated at the boiling point chy et al.[11]derived analytical solutions for the integra-corresponding to adsorption pressure [10],(b)normal tions of the Dubinin/Radushkevich and Dubinin/Astakhov boiling point molar volume [14],or,more generally,(c)the equations to calculate spreading pressures.Their D/R-afﬁnity coefﬁcient b of Dubinin [2,4].This theory for Ideal Adsorbed Solution equation for spreading pressure is:mixtures states that:o ](RT /b )ln(x f /f )5(RT /b )ln(x f /f )5etc.(10)Œ111s 1222s 2W b E p x p RT o i o i sat i]]]]]]]P 512erfln S D SF S DGDS D i 2V RTb E p m i i o iFugacities f (and f for saturated vapors)used by Grant i i s and Manes for high-pressure gases can be replaced with (13)partial (and saturated vapor)pressures p or concentrations i where erf is the classical error function,which can beC at normal atmospheric conditions.i approximated [16]by the series:Grant and Manes [14]used the additivity of molar volumes:35792x x x x ]S ]]]]DV 5n S x V (11)erf(x )5x 21212 (14)]T T i m iŒ31042216p234G .O .Wood /Carbon 40(2002)231–239(Note:The negative sign before the erf is incorrect in Eq.single organic vapor mixtures [18,20,21].Beneﬁts of the (12)of Ref.[11],but correct in the Appendix derivation.)Doong/Yang simple volume exclusion model include:(a)In applying this model,spreading pressures for the com-solvable by simple matrix solutions without the need for ponents are balanced by adjusting the mole fractions,iteration,even for multiple components,and (b)yielding which must add up to unity.The common factor both distributions and quantities of adsorbed mixture (W E œp /2RT )is eliminated in setting the spreading components without a second equation.o o pressures equal to one another.This Myers/Prausnitz–Dubinin (or IAST–D/R)theory 2.6.Proportionality theorieshas the added advantage of not requiring the reference pure vapor isotherm to be at the same temperature as the The simplest model for predicting adsorption capacities mixture.It was found to work well with miscible mixtures of mixtures from known distributions (or distributions from of chlorobenzene/carbon tetrachloride [11],1,2-dichloro-total binary mixture capacity)is the Molar Proportionality ethane/benzene [17],and the ternary mixture carbon Model (or Method).It incorporates the assumption that the tetrachloride/chlorobenzene/2-chloropropane [18].Multi-amounts adsorbed from a vapor mixture are proportionalocomponent breakthrough times and curves,as well as by adsorbate mole fractions to the amounts n that would i adsorbed capacities at equilibrium,were successfully pre-have been adsorbed from a pure vapor at the same partial dicted.vapor pressure (or concentration).In other words,the A volumetric form of the IAST can be called the different components do not interact except to ‘deny’Volumetric Adsorbed Solution Theory (V AST).Since adsorption to one another.This assumes a limited number molecules of mixture components occupy different vol-of moles (adsorption sites or surface area)can be covered umes,their evaporation rates and corresponding pressures (the Langmuir isotherm assumption).For a binary vapor should be proportional to volume fractions,not mole mixture (two vapors excluding air components)the total n T fractions (all intermolecular interactions being equal).and individual amounts (e.g.mol/g)n adsorbed according i Also,since activated carbon is a volume ﬁlling sorbent,we to Molar Proportionality is:should have a ‘ﬁlling pressure’,rather than a spreading o on 5x n 1x n (16)T 1122pressure.Eq.(13),then,can be used to equate ﬁlling pressures and calculate volume fractions,which can be This can easily be extended to any number of vapor converted to mole fractions by knowing partial molar components.Similarly,Volume Proportionality states:volumes in the corresponding mixture.o oV 5z V 1z V (17)As with the Polanyi Adsorbed Potential Theory,which T 1122also gives adsorbed mixture component distributions,the For volume fractions z .Any single-vapor isotherm,IAST and V AST require a second equation to determine i including the D/R,can be used to calculate the pure vaportotal and component adsorbed capacities.o oadsorption capacities n or volumes V .For example,i i Jonas et al.[22]used the D/R isotherm with carbon 2.5.Exclusion theoriestetrachloride as the reference compound to predict in-dividual and total adsorption volumes (and corresponding Models based on exclusion assume that each adsorbategravimetric capacities in g/g carbon)from gas phase (not in a mixture reduces the sorbent available for adsorbing the adsorbed phase)mole fractions by the Molar Propor-other(s).In Molar Exclusion the adsorbates reduce the tionality Method.They found fair agreement (210to number of surface sites or area;in Volume Exclusion they 120%individual deviations)with experimental kinetic reduce adsorption volume.The adsorbates are still consid-capacities obtained from slopes of plots of 1%break-ered independent and existing as if they are in the pure through times vs.carbon bed weights.state;only the area or volume to be ﬁlled is less for each because of the presence of the other.Doong and Yang [19] 2.7.Standard state optionsproposed a Volume Exclusion Model for the D/R equation,such that for component 1of a binary mixture:The Lewis,Proportionality,and Exclusion Models are 2all interpolations between capacities of the pure com-p RTs1o ]]]V 5W 2V exp2ln (15)s d F SD G1o 2ponents.The pressures p and/or reference standard b E p i1o 1oo pressures p at which these pure component capacities n s i i where V and V are the micropore volumes occupied by are to be calculated by Eq.(1)is up for discussion.The 12adsorbed mixture components 1and 2from the total ﬁrst option is the Single Vapor Isotherm (SVI),where o micropore volume W .If the D/R isotherms for the pure p 5p ,the partial vapor pressure of component i in o i i o o components show signiﬁcantly different micropore vol-equilibrium with the mixture,and p 5p ,the saturation s i sat i umes,W and W ,these can be used.This and other vapor pressure of pure i .The second is the Ideal Adsorbedo1o2o o oexclusions models have been used for immiscible water–Solution (IAS)assumption,where p 5p /x or p 5x p i i i s i i sat iG.O.Wood/Carbon40(2002)231–239235 (not both).Similarly,the third is the Ideal Volumetric D/R parameters used for model comparisons.Afﬁnity oSolution(IVS),where p5p/z for volume fractions z.coefﬁcients were calculated from molecular parachors[6].i i i iFrom the Lewis correlation we also have the possibilityothat the reference capacities n should be calculated at the ponent molar volumesiototal pressure,so that p5S p.In this paper we willi iexplore these options with the abovementioned models.In applying the models discussed above a question iswhat to use for component molar volumes V in adsorbedm imixtures.Data on volume changes upon mixing vs.parisons mixture composition are necessary for exact values;how-ever,they are seldom available.On the other hand,molar 3.1.Database selection volumes of pure liquids are readily calculated from liquidodensities d and molecular weights M as V5M/d.L w m i w L Criteria for selecting mixture equilibrium adsorption Doong and Yang reviewed other equations for estimatingdata for testing of predictive models required listings of:molar volumes above normal boiling points[19].Since(a)D/R parameters of the pure components(or data from one goal of our work is to predict adsorption capacities ofwhich they could be derived);(b)vapor phase pressures of components of a wide variety of liquid mixtures using acomponents in adsorbed mixtures;(c)adsorbed phase minimum amount of input data,which must be readilycapacities and distributions;(d)information on conditions,available,in this paper we choose to use pure liquid molarsuch as temperature;and(e)an activated carbonaceous volumes(20–258C),even for components of adsorbedsorbent.Four sources of data meeting these criteria were mixtures.selected:Lavanchy et al.[11]published such data for20binary mixtures of chlorobenzene and carbon tetrachlorideon an activated carbon at298K.Stoeckli et al.[17] 4.Results and analysestabulated data for18benzene and1,2-dichloroethanemixtures on the same carbon at293K.Xie et al.[9] 4.1.Total capacity calculation comparisonspublished42data for three binary mixtures(benzene–hexane,benzene–pentane,and hexane–pentane)on an Theﬁrst test of the models discussed above with theactivated carbon and a carbon molecular sieve.Hoppe and options and data discussed above was how well theirWorch[23]published gas phase pressures and adsorbed calculated total adsorbed mixture capacities compared withphase capacities for13mixtures of benzene and iso-reported total capacities.Calculations were done for eachpropanol at303K.Although the latter did not give the of the21models and options listed in Table2and each ofD/R parameters for the pure components,they did list the93mixtures.Average and Standard Deviations fromcalculated pure component spreading pressures/RT for the experimental values are listed in Table2;thesevapor pressures400–4800Pa.From the benzene spreading represent measures of accuracy and precision,respectively.pressures and Eq.(13)we calculated a best-ﬁt reference Table2shows that the best(and equivalent)precisionsadsorption potential of E510.29kJ/mol and micropore of the model predictions were obtained for the Volume o3volume of W50.517cm/g.This gave a total of93Proportionality,Molar Proportionality,Lewis,and Bering1 obinary mixtures to study.Table1lists the mixtures and models with the Ideal Adsorbed Solution and Ideal Volu-Table1Mixtures and D/R parameters used for calculationsBinary mixture components Carbon designation Dubinin/Radushkevich isotherm parameters Data(Benzene reference)sourceMicropore Adsorption Afﬁnity Ref.volume potential coefﬁcients3(cm/g)(kJ/mol)Chlorobenzene–carbon tetrachloride Activated carbon U-020.44817.00 1.17,1.06[11] Benzene–1,2-dichloroethane Activated carbon U-020.44817.00 1.00,0.91[17] Benzene–hexane Carbon mol sieve J-10.46918.70 1.00,1.28[9] Benzene–pentane Carbon mol sieve J-10.46918.70 1.00,1.11[9] Hexane–pentane Carbon mol sieve J-10.46918.70 1.28,1.11[9] Benzene–hexane Activated carbon GH-280.60215.20 1.00,1.28[9] Benzene–pentane Activated carbon GH-280.60215.20 1.00,1.11[9] Hexane–pentane Activated carbon GH-280.60215.20 1.28,1.11[9] Benzene–isopropanol Activated carbon B-40.51710.29 1.00,0.82[23]236G.O.Wood/Carbon40(2002)231–239o Table2The Single Vapor Isotherm option[(´5RT S z ln(p/T i sat i Total capacity of mixtures calculations:models’average devia-p)]produced worse precisions and accuracies in these fouritions(accuracy)and standard deviations(precision)from ex-models.perimental values for93binary mixtures The Volume and Molar Exclusion models’predictions Model and option Total capacity(mmol/g)were signiﬁcantly worse than those of the four best,yielding results equivalent to one another due to theAverage Std Devassumption that molar volumes were the same in mixtures Volume proportionality–SVI20.3180.47as in the pure states.Bering2model predictions were Volume proportionality–IAS0.0080.38signiﬁcantly worse that those for the original Bering1 Volume proportionality–IVS20.0030.38model.Molar proportionality–SVI20.2930.46Molar proportionality–IAS0.0240.384.2.Mole fraction(distribution)modelsMolar proportionality–IVS0.0320.38Lewis–SVI20.3620.50The second test was of those models that can calculate Lewis–IAS20.0080.38Lewis–IVS20.0080.38distributions of adsorbed mixture components,in some Bering1–SVI20.3040.47cases starting with calculated or experimentally known Bering1–IAS20.0030.38total adsorbed molar capacities.Table3lists these models Bering1–IVS20.0010.38with options and resulting measures of accuracy and Bering2–SVI20.4640.63precision in applying them to data.It also lists the numbers Bering2–IAS0.0510.42of the93binary mixtures for which we were able to Bering22IVS0.0430.42calculate mole fractions between0and1.Only results for Molar exclusion–SVI0.1680.46one component of each binary mixture were used for these Molar exclusion–IAS0.4980.79measures,since the same results would be obtained for the Molar exclusion–IVS0.5400.81other of each pair.To avoid the effect of which component Volume exclusion–SVI0.1680.46Volume exclusion–IAS0.4980.79was chosen from each binary mixture,we averaged the Volume exclusion–IVS0.5400.81absolute values of model residuals(calculated minusexperimental mole fraction for one of the components). SVI5Single vapor isotherm;IAS5ideal adsorbed solution;Table3shows that only four of these models were able IVS5ideal volumetric solution.to calculate molar distributions for all93mixtures:IAST, metric Solution options.Of these,the Bering1mixture V AST,Polanyi,and Volume exclusion–SVI.Of these,the isotherm Eq.(2)with the Ideal Volumetric Solution option best accuracy and precision were found for the IAST and o[´5RT S z ln(z p/p)]had the best average accuracy.the worst for Volume exclusion–SVI;for V AST and T i i sat i iTable3Molar distribution calculations:models’average absolute deviations(accuracy)and standard deviations(precision)of component calculated mole fractions from experimental values for one selected component of each binary mixtureAverage Standard Number ofabsolute deviation of mixtures thatvalue of residuals could beresiduals calculatedLewis–SVI0.6590.26731Lewis–IAS0.6640.33843Lewis–total pressure0.7310.32463Molar proportionality–SVI0.6620.28031Molar proportionality–IAS0.6710.37643Molar proportionality–total pressure0.8030.38363Ideal adsorbed solution theory0.0540.07193 Volumetric adsorbed solution theory0.0720.09093Polanyi adsorption potential theory0.0720.08893Molar exclusion–SVI0.2860.40288Molar exclusion–IAS0.1920.22653Molar exclusion–IVS0.1950.22953Volume exclusion–SVI0.0920.11193Volume exclusion–IAS0.1350.15788Volume exclusion–IVS0.1370.16088SVI5Single vapor isotherm;IAS5ideal adsorbed solution;IVS5ideal volumetric solution.G.O.Wood/Carbon40(2002)231–239237 Polanyi they were intermediate and very similar.TheLewis and Molar proportionality models’calculated molefractions are very sensitive to the values of total andreference moles input,which explains their poor perform-ances.One other option that was tried with the IAST andPolanyi models was mole fraction weighting of the afﬁnitycoefﬁcient:b5S x b(j includes i).This producedi j jmuch worse accuracy and precision measures than usingindividual pure component b.ibined equation modelsThe third test was to calculate both experimental dis-tributions and experimental total capacities by combiningtwo equation models:(a)IAST,V AST,and Polanyi modelsparison of calculated and experimental capacities of were used to calculate the mole fractions of binary186components of binary adsorbed mixtures using the IAST–D/ components;(b)then the equations and options listed inR–Bering1–IAS combination of equations and options.The linear theﬁrst column of Table4were used to calculate total andleast squares slope(forced zero intercept)and squared correlation component adsorbed capacities.The latter were then coefﬁcient quantify average accuracy and precision,respectively. compared with reported experimental values.Table4shows measures of accuracy(average deviations from obtained with carbon tetrachloride and isopropanol.Devia-experimental values)and precision(standard deviations).tions include both experimental and model errors.Table4shows that the two models with the best(andsame)combination of accuracy and precision measureswere the IAST–Lewis–IAS and IAST–Bering1–IAS 5.Conclusions and discussioncombinations.The Polanyi model usually had better aver-age accuracy,but worse precision.The Ideal Volumetric We conclude from this study that the best model for Solution assumption gave no better(often worse)results calculating equilibrium molar distributions of components than the Ideal(Molar)Adsorbed Solution assumption.of adsorbed binary mixtures of organic compounds using Likewise,V AST was no improvement over IAST.known single-component Dubinin/Radushkevich isotherm Fig.1shows a comparison of component capacities for parameters is the Ideal Adsorbed Solution Theory.An both components of the93binary mixtures calculated by analytical solution(Eq.(13))for the necessary isotherm the IAST–Bering1–IAS combination model with ex-integrations(Eq.(12))avoids the problem of no Henry’s perimental values.The largest positive deviations were Law limit.The error function(erf)in this solution can beTable4Combined models’average deviations(accuracies)and standard deviations(precisions)of calculated component capacities from experimental values for both components of93binary mixturesModel and option IAST V AST PolanyiAverage Standard Average Standard Average Standarddeviation deviation deviation deviation deviation deviation(mmol/g)(mmol/g)(mmol/g)(mmol/g)(mmol/g)(mmol/g) Volume proportionality–IAS0.01440.3180.04080.49720.00180.395 Volume proportionality–IVS0.01500.3180.02540.40220.01760.449 Molar proportionality–IAS0.02400.3180.03620.4070.01080.391 Molar proportionality–IVS0.02880.3200.03510.4040.01430.391 Lewis–IAS0.01390.3180.02360.40220.00260.395 Lewis–IVS0.01460.3180.02520.40220.00260.396 Bering1–IAS0.01390.3180.02440.40220.00260.395 Bering1–IVS0.01470.3180.02520.48620.00180.395 Bering2–IAS0.03220.3240.04640.4080.00560.401 Bering2–IVS0.02860.3250.02680.4550.00180.403 IAS5Ideal adsorbed solution;IVS5ideal volumetric solution.。

Abiotic degradation of four phthalic acid esters in aqueous phase under natural sunlight irradiation

Journal of Environmental Sciences21(2009)285–290Abiotic degradation of four phthalic acid esters in aqueous phase undernatural sunlight irradiationRuttapol Lertsirisopon,Satoshi Soda,Kazunari Sei,Michihiko Ike∗Division of Sustainable Energy and Environmental Engineering,Graduate School of Engineering,Osaka University,2-1Yamada-oka,Suita565-0871,Osaka,Japan.E-mail:ike@see.eng.osaka-u.ac.jpReceived24April2008;revised02June2008;accepted17June2008AbstractAbiotic degradability of four phthalic acid esters(PAEs)in the aquatic phase was evaluated over a wide pH range5–9.The PAE solutions in glass test tubes were placed either in the dark and under the natural sunlight irradiation for evaluating the degradation rate via hydrolysis or photolysis plus hydrolysis,respectively,at ambient temperature for140d from autumn to winter in Osaka,Japan. The eﬃciency of abiotic degradation of the PAEs with relatively short alkyl chains,such as butylbenzyl phthalate(BBP)and di-n-butyl phthalate(DBP),at neutral pH was signiﬁcantly lower than that in the acidic or alkaline condition.Photolysis was considered to contribute mainly to the total abiotic degradation at all pH.Neither hydrolysis nor photolysis of di-ethylhexyl phthalate(DEHP) proceeded signiﬁcantly at any pH,especially hydrolysis at neutral pH was negligible.On the other hand,the degradation rate of di-isononyl phthalate(DINP)catalyzed mainly by photolysis was much higher than those of the other PAEs,and was almost completely removed during the experimental period at pH5and9.As a whole,according to the half-life(t1/2)obtained in the experiments,the abiotic degradability of the PAEs was in the sequence:DINP(32–140d)>DBP(50–360d),BBP(58–480d)>DEHP(390–1600d) under sunlight irradiation(via photolysis plus hydrolysis).Although the abiotic degradation rates for BBP,DBP,and DEHP are much lower than the biodegradation rates reported,the photolysis rate for DINP is comparable to its biodegradation rate in the acidic or alkaline condition.Key words:phthalic acid esters;abiotic degradation;photolysis;hydrolysis;ﬁrst-order kineticsDOI:10.1016/S1001-0742(08)62265-2IntroductionIn recent years,considerable attention has been paid totoxicity and degradability of phthalic acid esters(PAEs)(Staples et al.,1997),which have been frequently de-tected throughout aquatic environment(Fromme et al.,2002;Yuan et al.,2002).PAEs undergoing hydrolysis,photolysis,and aerobic/anaerobic biodegradation could beremoved from aquatic environment.Among those diﬀerentdegradation processes,relatively abundant data are avail-able on biodegradation of PAEs(Chang et al.,2007;Liet al.,2005;Yuan et al.,2002;Wang et al.,1996,2000).On the other hand,limited information has been knownon the abiotic processes(hydrolysis and photolysis).Thereare several researchers who have focused on photolysis ofPAEs using artiﬁcial irradiation sources,such as xenon arclamps(Bajt et al.,2001),mercury lamps(Mailhot et al.,2002),and ultraviolet light(Lau et al.,2005),to cleanup the PAEs-contaminated water.However,those irradi-ation sources had very diﬀerent radiation intensities andwavelength distributions from natural sunlight irradiation.As a rare study for describing the abiotic degradation of*Corresponding author.E-mail:ike@see.eng.osaka-u.ac.jpPAEs under natural aquatic environment,Gledhill et al.(1980)have reported that butylbenzyl phthalate(BBP)exposing to sunlight irradiation for28d resulted in lessthan5%degradation,but limited information is availableto date.Wolfe et al.(1980)inferred that according to amathematical model data the photolysis is the primarydegradation process of PAEs in oligotrophic lakes.Forbetter understanding of the fate of PAEs in aquatic envi-ronment,there is a need to conduct more realistic studieson abiotic degradation with natural solar intensity.The aim of this study was to assess the contributionof abiotic degradation of PAEs under the sunlight irra-diation at ambient temperature over a wide pH rangethat normally found in natural aquatic environments.Fourcommercial PAEs(BBP,di-n-butyl phthalate(DBP),di-ethylhexyl phthalate(DEHP),and di-isononyl phthalate(DINP)),were subjected to the abiotic degradation tests,and the half-lives of the PAEs by hydrolysis and photolysiswere estimated by theﬁrst-order degradation kinetics.Therole of abiotic degradation in the fate of the PAEs wasdiscussed by comparing the estimated half-lives with thoseby aerobic/anaerobic biodegradation reported previously.286Ruttapol Lertsirisopon et al.V ol.211Materials and methods1.1Phthalic acid eatersAnalytical grade BBP(Tokyo Chemical,Japan),DBPand DEHP(Kishida Chemical,Osaka,Japan),and DINP(Wako,Osaka,Japan)were utilized in the abiotic degra-dation tests.BBP and DBP are suspected to be endocrinedisruptors(Jobling et al.,1995;Harris et al.,1997;Beres-ford et al.,2000).DEHP is a probable human carcinogen(class B)and BBP is a possible human carcinogen(class C)(USEPA,2000).DINP is one of the PAEs with the largestproduction rate as well as DEHP.1.2Abiotic degradation testsOutdoor experiments were carried out on the roof ofa building of Department of Environmental Engineering,Graduate School of Engineering,Osaka University,Japan(34◦N,135◦E)for140d from September2004to March2005.All the selected PAEs were prepared at total organiccarbon(TOC)concentration of100g/L in artiﬁcial riverwater(g/L deionized water)(K2HPO421.8,KH2PO48.5,Na2HPO444.6,NH4Cl1.7,MgSO4·7H2O22.5,CaCl2 27.5,and FeSO4·6H2O0.25).The concentration of BBP, DBP,DEHP,and DINP at100g TOC/L corresponds to0.44,0.52,0.35,and0.32mmol/L,respectively.Sincesolubility of the PAEs is extremely low,the solutionswere treated by an ultrasonicator(TOMY UD201,Seiko,Japan)with output20kHz and stirred for several hoursfor homogenization.The pH value was adjusted by HClor NaOH to designed pH value(5.0,6.0,7.0,8.0,and9.0).A30-mL of the solution was placed in a50-mLpyrex glass test tube(IWAKI,Chiba,Japan)in duplicate.All tubes were sealed tightly with a rubber stopper.Thetest tube was in2-mm thick and90%–100%transparentfor solar radiation.All test tubes were divided into twogroups,one was exposed to the sunlight irradiation and theother was covered with aluminum foil to keep in the darkat the same place.The radiation energy and the ambienttemperature were measured by a pyranometer EKO MS-802(EKO Instruments,Japan).1.3Analytical proceduresA0.75-mL was periodically sampled from the testtube and mixed with0.75mL acetonitrile to extract thePAE,followed by centrifugation(15000×g)to obtainsupernatant.The0.75mL of supernatant was used for thePAE analysis by high performance liquid chromatography(HPLC).The HPLC apparatus consisted of two LC-10ADvp solvent delivery pump with a DGU-14A solventcontroller and a SPd−10Avp UV-Vis spectrophotometricdetector connected to an advanced computer interface forthe analyses by a chromatography workstation(LCsolu-tion,ver.1.02J,Shimadzu,Japan).Samples were injectedvia a SIL-10AF autosampler into Shim-pack VP-ODScolumn(150mm×4.6mm,i.d.5μm;Shimadzu,Kyoto)with the mobile phase of acetonitrile and water mixture(90:10,V/V)at aﬂow rate of0.5mL/min.The PAEs weredetected by the UV detector at a wavelength of254nm.The errors in the PAEs measurements were less than5%. 2Results2.1Daily changes of radiation energy and ambienttemperatureThe daily average radiation and ambient temperature widely varied from17.1to242.8W/m2(107.9W/m2by mean)and0.4to27.4°C(10.8°C by mean)(Fig.1).These conditions can reﬂect a moderate autumn and winter in Japan in the temperate zone.2.2Abiotic degradationThe results of the abiotic degradation tests of the PAEs at diﬀerent initial pH values are shown in Fig.2.The pH value of the mixture did not change signiﬁcantly during the experimental period.The PAE concentrations in the dark were aﬀected only by hydrolysis,while those under the sunlight irradiation were aﬀected by both hydrolysis and photolysis.Degradation of all the PAEs proceeded slowly in the dark,and more than80%of the initial concentration remained after140d at all pH,especially degradation of DEHP and DINP in the dark was negligible at neutral pH. On the other hand,BBP,DBP,and DINP demonstrated the relatively high abiotic degradation rate under the sunlight irradiation at acidic and alkaline pH values compared with those under the dark condition,suggesting the higher photolysis rate than the hydrolysis rate of the three PAEs. DINP was eﬀectively degraded under sunlight irradiation even at neutral pH,where more than50%was removed. BBP and DBP were degraded by about20%under same condition.On the other hand,DEHP degradation proceed-ed slowly even under sunlight irradiation at any pH,and more than80%of its initial concentration remained even after140d.Any distinctive intermediate could not be detected under the experimental condition.2.3Kinetic analysisAlthough there was a large variation in solar radia-tion and temperature during the experimental period,the abiotic degradation curves could be well described by theﬁrst-order kinetic model compared to the zero-order kinetic that could also describe the abiotic degradation under dark condition.Theﬁrst-order kinetic parameters(k) and half-lives(t1/2)are estimated and summarized in Table 1,and the simulated degradation curves are described in Fig.2.The k values and half-lives determined for degradation under sunlight irradiation represent typical values for the abiotic PAEs degradation under moderate or calm climates such as autumn or winter in Osaka,Japan. According to the kinetic analysis,abiotic degradation of the four PAEs would be ranked by half-lives as:BBP(390–1500d) DBP(430–1300d)>DINP(>460d) DEHP (>830d)in the dark and DINP(32–140d)>DBP(50–360 d),BBP(58–480d)>DEHP(390–1600d)under sunlight irradiation.No.3Abiotic degradation of four phthalic acid esters in aqueous phase under natural sunlight irradiation287Fig.1Daily average radiation and ambient temperature at Osaka from September 2004to March 2005.Experiments were beaked by typhoons (A)and equipment maintenance(B).Fig.2Degradation of the PAEs in sunlight irradiation (upper panels)and in the dark (lower panels)at pH 5,6,7,8,and 9.The regression lines by ﬁrst-order kinetics are shown.DBP:di-n -butyl phthalate;BBP:butylbenzyl phthalate;DEHP:di-ethylhexyl phthalate;DINP:di-isononyl phthalate.3DiscussionThis research aimed at assessing the contribution of abiotic degradation of the PAEs to total degradation in aquatic environment.The abiotic degradation tests were carried out for selected PAEs at ambient temperature in the dark and under natural sunlight irradiation.Degradation observed in the former test refers to hydrolysis solely,while that in the latter test to hydrolysis plus photolysis,that is total abitotic degradation.The half-lives of the PAEs by abiotic degradation under ambient conditions which have been reported previously (Table 2).Our resultsconsist with the previous data that PAEs are hydrolyzed at negligible rates and photolysis is minor degradation in aquatic environment at neutral pH.Fig.3illustrates the contribution of hydrolysis and photolysis and pH to total abiotic degradation of each PAE during 140d experiment.It could be said,as a whole,that photolysis is the main process for abiotic PAE degradation and the acid-and alkali-catalyzed photo-hydrolysis processes enhance abiotic degradation considerably.The e ﬀect of pH on the abiotic degradation rate was rarely reported in aquatic u et al .(2005)reported that the rates of DBP degradation were high at288Ruttapol Lertsirisopon et al.V ol.21Table 1Kinetic parameters for abiotic degradation of the PAEs under sunlight irradiation and dark conditionsCondition pHDBPBBPDEHPDINPk(d −1)t 1/2(d)k (d −1)t 1/2(d)k (d −1)t 1/2(d)k (d −1)t 1/2(d)Sunlight5 1.4×10−250 1.2×10−258 1.8×10−3390 2.1×10−2326 1.0×10−2669.3×10−375 1.3×10−3550 1.3×10−2527 1.9×10−3360 1.5×10−3480 4.4×10−41600 4.9×10−314087.3×10−394 6.9×10−31009.9×10−4700 1.1×10−2619 1.2×10−257 1.0×10−268 1.5×10−3460 1.9×10−236Dark5 1.4×10−3510 1.6×10−34408.2×10−48409.6×10−47206 1.1×10−3620 1.2×10−3600 5.6×10−41300 5.9×10−412007 5.3×10−41300 4.6×10−415000–0–8 1.3×10−3530 1.5×10−3480 6.8×10−41000 6.9×10−4100091.6×10−34301.8×10−33908.4×10−48301.5×10−4460All the regression resulted in r 2>0.99.Table 2Abiotic degradation half-life of the PAEs (d)DBPBBP DEHP DINP ReferenceHydrolysis 3650–730000–Wolfe et al .,1980a –>100––Gledhill et al .,1980bPhotolysis880–4450–73–550–Wolfe et al .,1980;Howard 1991c –>100––Gledhill et al .,1980d–:No data;a based upon overall rate constant at pH 7and 30°C;b aqueous solutions under dark conditions for 28d;c scientiﬁc judgment based upon estimated rate data for alkylperoxy radicals in aqueous solution;d Sunlight exposure in aqueous solutions for 28d.Fig.3Contribution of hydrolysis and photolysis on abiotic degradation of the PAEs under di ﬀerent initial pH after 140d tested period.both the highest pH value (pH =10)and lowest pH (pH =3)under UV irradiation at the initial concentration of 600g TOC /L for 60min.According to the degradation model of DBP (Fig.4),the major degradation pathway of DBP involves the hydrolytic photolysis of the carbon in the α-and /or β-position of the ester chain with the production of aromatic carboxylic derivatives (Lau et al .,2005).As the pH is elevated to the alkali range,a simpleNo.3Abiotic degradation of four phthalic acid esters in aqueous phase under natural sunlight irradiation289Fig.4Model of degradation mechanism of DBP photolysis at diﬀerent pH(Lau et al.,2005).Six diﬀerent pathways are marked by numbers.The mechanisms are divided into3major pathways depending on the pH level.Aαand Aβ:acidic catalysis at pH3;Hβ:hydrolysis;H butyl:oxidation/reduction of the butylchain at pH5;Bα:basic catalysis when pH>>7.cleavage dominates the degradation process through a photochemical homolyric decarboxylation.Additionally, multi-degradation pathways explain the fast acid-catalyzed hydrolytic photolysi.This model possibly explains the results of abiotic degradation of the PAEs.However,both hydrolysis and photolysis were not eﬀective for DEHP at acidic/alkaline pH,i.e.,abiotic degradability of DEHP is low at ordinal conditions like in the ranges of solar radiation,temperature and pH tested here.The other three PAEs could be readily degraded under acidic and alkaline conditions mainly via photolysis.DINP could be eﬃciently degraded even at neutral pH.In contrast, the abiotic degradation of BBP and DBP was signiﬁcant-ly ineﬀective compared with that under acidic/alkaline conditions.Therefore,abiotic degradation of DINP might proceed readily regardless of pH when sunlight irradiation is available.It could partly explain that there is no apparent contamination of aquatic environment by DINP in contrast to frequent detection of DEHP,even though DINP is one of the PAEs with the largest production as well as DEHP. The detection,identiﬁcation,and toxicity evaluation of the intermediates are needed for further studies,although no distinctive intermediate in abiotic degradation of the PAEs could be detected in current experimental conditions.In order to discuss the abiotic degradation contributions to the fate or disappearance of the PAEs in aquatic envi-ronment,the half-lives of PAEs by biodegradation which have been reported previously(Table3)were used for comparison with those determined in this study(Table1). Since there have been rarely reported on the biodegra-dation half-lives under acidic/alkaline condition,the data only determined at neutral pH are listed in Table3.Under the aerobic condition,BBP and DBP can be biodegraded by half-lives of a few days,whereas,more than weeks or months are required for DEHP and DINP.The half-lives in the anaerobic condition are2–10times longer than those in aerobic conditions.Photolysis and aerobic degradation occurs simultaneously in the surface layer of aquatic environment.The biodegradation half-lives of the PAEs are much shorter than abiotic degradation at neutral pH,suggesting that biodegradation would be the main process to remove the PAEs from aquatic environment when the aqueous phase is neither acidic nor alkaline. However,low or high pH could lower the microbial activities.Lertsirisopon et al.(2003)reported that the half-lives of BBP,DBP,DEHP and DINP increased about20% under aerobic condition(pH5–9).Chang et al.(2005) have also reported that about15%increase in the half-290Ruttapol Lertsirisopon et al.V ol.21Table3Biodegradation half-life of the PAEs in aquatic systems(d)Condition DBP BBP DEHP DINP ReferenceAerobic0.5–10.10.5–10.57.3–27.5Yuan et al.,2002a 1–32–42–5Fujita et al.,2005b2–54–116–217–40Lertsirisopon et al.,2003c Anaerobic8–1414–33>1300Painter and Jones,1990d11.7–18.99.9–25.529.9–39.1Yuan et al.,2002e2–32–3>208>347Lertsirisopon et al.,2006f a Unacclimated river sediment samples at pH7.0;b unacclimated river,pond,or activated sludge samples at pH7.2,and28°C;c unacclimated pond water samples at28°C;d unacclimated sludge at30°C;e unacclimated river sediment microcosms at pH7and30°C;f natural sediment microcosms at pH7and28°C.lives of BBP and DEHP by anaerobic degradation wasobserved at low or high pH(pH5–9).In contrast,ourstudy showed that abiotic degradability of the PAEs wasconsiderably enhanced under the acidic and alkaline condi-tions.Therefore,the contribution of abiotic degradation todisappearance of the PAEs will increase when pH becomesacidic or alkaline.Even so,the disappearance of BBP,DBP and DEHP might highly depend on biodegradationunless pH becomes extremely acidic/alkaline judging fromcomparison of the half-lives.However,abiotic degradation(photolysis)would play a signiﬁcant role in removal ofDINP in acidic(pH<6)or alkaline(pH>8)conditionsinstead of biodegradation.4ConclusionsThe abiotic degradation tests under the sunlight ir-radiation over a wide pH range were carried out toestimate the contribution of hydrolysis and photolysis todegradation of the PAEs in aquatic environment.Theexperiments gaveﬁndings that abiotic degradation ofthe PAEs occurs mainly by photolysis under acidic andalkaline conditions rather than neutral pH,as a wholetrend.According to theﬁrst-order kinetics analysis,theabiotic degradability(hydrolysis plus photolysis)of thePAEs in aquatic environment would be ranked as DINP >DBP,BBP>DEHP.Although the abiotic degradation rate for BBP,DBP,and DEHP is considered much smallerthan their biodegradation rate when pH is not extremelyacidic/alkaline,the photolysis rate for DINP is comparablewith its biodegradation rate in aquatic environment.DINPin aquatic environment would be degraded mainly byphotolysis in both acidic and alkaline conditions but bymicroorganisms at neutral pH.ReferencesBajt O,Mailhot G,Bolte M,2001.Degradation of dibutyl phthalate by homogeneous photocatalysis with Fe(III)in aqueous solution.Applied Catalysis B:Environmental,33:239–248.Beresford N,Routledge E J,Harris C A,Sumper J P,2000.Issues arising when interpreting results from an in vitro assay for estrogenic activity.Toxicology and Applied Pharmacology,162:22–33. Chang B V,Liao C S,Yuan S Y,2005.Anaerobic degradation of diethyl phthalate,di-n-butyl phthalate,and di-(2-ethylhexyl)phthalate from river sediment in Taiwan.Chemosphere,58:1601–1607. Chang B V,Wang T H,Yuan S Y,2007.Biodegradation of four phthalate esters in sludge.Chemosphere,69:1116–1123.Fromme H,K¨u chler T,Otto T,Pilz K,M¨u ller J,Wezel A,2002.Occurrence of phthalates and bisphenol A and F in the environ-ment.Water Research,36:1429–1438.Fujita M,Ike M,Ishigaki T,Sei K,Jeong J S,Makihira N,Lertsirisopon R,2005.Biodegradation of three phthalic acid esters by microor-ganisms from aquatic environment.Japanese Journal of Water Treatment Biology,41:193–201.Gledhill W E,Kaley R G,Adams W J,Hicks O,Michae P R,Saeger V W,LaBlanc G A,1980.An environmental safety assessment of butyl benzyl phthalate.Environmental Science and Technology,14: 301–305.Harris C A,Henttu P,Parker M G,Sumpter J P,1997.The estrogenic activity of phthalate esters in vitro.Environmental Health and Perspectives,105:802–811.Howard P H,Boethling R S,Jarvis W F,Meylan W M,Michanlenko E M,1991.Handbook of Environmental Biodegradation Rates.MI: Lewis Publishers.Jobling S,Reynolds T,White R,Parker M G,Sumpter J P,1995.A variety of environmentally persistent chemicals,including some phthalate plasticizers,are weakly estrogenic.Environmental Health and Perspectives,103:582–587.Lau T K,Chu W,Graham N,2005.The degradation of endocrine disruptor di-n-butyl phthalate by UV irradiation:A photolysis and product study.Chemosphere,60:1045–1053.Lertsirisopon R,Ike M,Fujita M,2003.Environmental factors aﬀecting degradation of phthalic acid n Waterqual2003IWA-Asia Paciﬁc Regional Conference.Ban Kok,Thailand.19–23. Lertsirisopon R,Soda S,Sei K,Ike M,Fujita M,2006.Biodegrability of four phthalic acid esters under anaerobic condition assessed using natural sediment.Journal of Environmental Sciences,18:793–796. Li J X,Gu J D,Pan L,2005.Transformation of dimethy phthalate, dimethyl isophthalate and dimethyl terephthalate by Rhodococccus rubber Sa and modeling the process using the modiﬁed Gompertz model.International Biodeterioration and Biodegradation,55: 223–232.Mailhot G,Sarakha M,Lavedrine B,Caceres J,Malato S,2002.Fe(III)-solar light induced degradation of diethyl phthalate(DEP)in aqueous solutions.Chemosphere,49:525–532.Painter S E,Jones W J,1990.Anaerobic bioconversion of phthalic acid esters by natural inocula.Environmental Technology,11:1015–1026.Staples C A,Peterson D R,Parkerton T R,Adams W J,1997.The environmental fate of phthalate esters:A literature review.Chemo-sphere,35:667–749.USEPA(United States Environmental Protection Agency),2002.List of substances on IRIS.In:United State Environmental Protection Agency,Integrated Risk System Information.Wang J L,Chen L J,Shi H C,Qian Y,2000.Microbial degradation of ph-thalic acid esters under anaerobic digestion of sludge.Chemoshere, 41:1245–1248.Wang J L,Liu P,Qian Y,1996.Biodegradation of phthalic acid ester by acclimated activated sludge.Environment International,22:737–741.Wolfe N L,Burns L A,Steen W C,e of linear fee energy rela-tionships and an evaluative model to assess the fate and transport of phthalate esters in the aquatic environment.Chemosphere,9:393–402.Yuan S Y,Liu C,Liao C S,Chang B V,2002.Occurrence and microbial degradation of phthalate esters in Taiwan river sediments.Chemosphere,49:1295–1299.。

高温对药物有何影响呢英文

高温对药物有何影响呢英文The Effects of High Temperatures on MedicationsIntroduction: High temperatures can have significant effects on the stability and potency of medications. It is important to understand these effects in order to ensure the safety and efficacy of drugs. This document will discuss the impact of high temperatures on medications and provide recommendations for proper storage and handling under hot conditions.1. Degradation of Active Ingredients: High temperatures can lead to the degradation of active ingredients in medications. Many medications are sensitive to heat and can break down when exposed to elevated temperatures. This degradation can result in a loss of potency or even render the medication ineffective. It is crucial to store medications in a cool and dry place to prevent this degradation.2. Alteration of Physical Properties: In addition to the degradation of active ingredients, high temperatures can also alter the physical properties of medications. Heat can cause changes in the solubility, dissolution rate, and particle size of the drug, which can impact its absorption and bioavailability. This can lead to unpredictable drug responses and potentially compromise patient safety.3. Increased Risk of Contamination: Heat can increase the risk of contamination of medications. High temperatures can promote the growth of microorganisms, such as bacteria and fungi, in drug products. Contaminated medications can lead to serious infections and adverse reactions in patients. It is essential to store medications in a controlled environment to prevent microbial growth and maintain their sterility.4. Potential for Chemical Reactions: Certain medications are prone to undergo chemical reactions when exposed to high temperatures. For example, heat can cause the breakdown of certain drug molecules or facilitate the formation of new compounds, which may be toxic or have unpredictable effects on patients. Proper storage and handling of medications can help minimize the risk of these chemical reactions.5. Specific Medications and their Susceptibility to Heat: While all medications can be affected by high temperatures to some extent, certain drugs are more susceptible than others. For instance, insulin, certain antibiotics, and biologic medications are known to be highly sensitive to heat. It is vital to be aware of the specific storage requirements for each medication and follow the manufacturer's instructions accordingly.Recommendations: To ensure the efficacy and safety of medications, it is essential to follow proper storage and handling practices, especially under high-temperature conditions. Here are some recommendations:1. Store medications in a cool and dry place, away from direct sunlight and sources of heat.2. Avoid exposing medications to extreme temperatures, such as inside hot cars or near heating appliances.3. Check the storage instructions provided by the manufacturer for individual medications and adhere to them.4. If traveling with medications, use insulated containers or cool packs to maintain a constant temperature.5. Dispose of any medications that have been exposed to high temperatures, as their effectiveness may be compromised.Conclusion:High temperatures can cause numerous adverse effects on medications, including active ingredient degradation, alteration of physical properties, increased risk of contamination, and potential chemical reactions. Following proper storage and handling practices is essential to ensure the effectiveness and safety of medications, particularly in hot climates. It is crucial for healthcare professionals and patients to be aware of these effects and take necessary precautions to preserve the quality of medications.。

发芽对高粱氨基酸及抗营养因子含量

张俊，张三杉，叶丹，等. 发芽对高粱氨基酸及抗营养因子含量的影响[J]. 食品工业科技，2022，43（1）：87−92. doi:10.13386/j.issn1002-0306.2021030365ZHANG Jun, ZHANG Sanshan, YE Dan, et al. Effects of Germination on the Content of Amino Acids and Anti-nutritional Factors of Sorghum Grain[J]. Science and Technology of Food Industry, 2022, 43(1): 87−92. (in Chinese with English abstract). doi:10.13386/j.issn1002-0306.2021030365发芽对高粱氨基酸及抗营养因子含量的影响张　俊1，张三杉1，叶　丹2，余梦玲1，雷　激1,*（1.西华大学食品与生物工程学院, 四川成都 610039；2.四川天味食品集团股份有限公司, 四川成都 610200）摘　要：为改善高粱营养品质，拓宽其在食品工业中的应用，本实验以白高粱为原料进行发芽，探讨高粱发芽过程中氨基酸组成、γ-氨基丁酸（γ-aminobutyric acid ，GABA ）含量、谷氨酸脱羧酶（glutamic acid decarboxylase ，GAD ）活性、植酸酶活性、植酸及单宁含量的变化规律。

结果表明：随着发芽时间延长，高粱氨基酸总量显著增加，60 h 达到最大值为5.694 g/100 g ，相较未发芽高粱增加了28.50%；赖氨酸含量在发芽72 h 达到最大值为0.157 g/100 g ，增加了21.71%；GAD 活性增强，GABA 含量增加，60 h 达到最大值为19.026 mg/100 g ，增加到5倍；植酸酶活性同样随着发芽时间的延长不断增强，促使植酸发生降解，植酸含量从94.85 mg/100 g 下降到52.44 mg/100 g ，降低了44.71%；单宁含量从1.07%降到0.14%，下降了86.92%。

S-Demethylation of Nitrogen Heterocycles (1 a)

0 HeteroCorporation
304
S.-F. Chen and R. P. Panzica
Vol. 18
Scheme 2 reaction sequence and provides the one-carbon unit (C2) for annulation to the imidazole moiety. We now turned our attention to the origin of 6. We envisaged three possible pathways for the formation of 5 and 6 as illustrated in Figure 1. The first pathway, pathway A,
J. Heterocyclic Chem., 18, 303 (1981).
Certain 4-substituted imidazo- and v-triazolo[4,5-d]pyridazines can act as substrates (2) or inhibitors (3,4) of salvage pathway enzymes and therefore have the potential to function as chemotherapeutic agents. One approach to their synthesis involves ring closure of 3-methylthio-4,5diaminopyridazine (3) (5) followed by nucleophilic displacement of the methylthio group (6). 3-Methylthio-4,5-diaminopyridazine (3) had been prepared (7) by methylation of 4,5-diaminopyridazine-3-thione (4). The thione 4, in turn, was synthesized from 4,5-diaminopyridazine-3-one (1) in the presence of phosphorus pentasulfide (P,S,) and pyridine at reflux (7). Attempts at scaling up this reaction according to the published procedure met with failure and therefore we turned our attention to a n alternate route to 3 via 3-chloro-4,5-diaminopyridazine (2). This heterocycle had been isolated (7) as a minor product in the catalytic reduction of 4,5-diamino-3,6-dichloropyridazine. Since 2 was desired in large quantities, it was prepared directly from 1. Treatment of 1 with phosphorus oxychloride (POCl,) and a catalytic amount of N,N-dimethylaniline furnished 2 in good yield. Conversion of chloroazines to their corresponding methylthio analogs with sodium methylmercaptide has been accomplished in various solvents (8). Our initial sol-

Degradation of atrazine by m

Journal of Hazardous Materials B138(2006)187–194Degradation of atrazine by microwave-assisted electrodelessdischarge mercury lamp in aqueous solutionNa Ta,Jun Hong,Tingfeng Liu,Cheng Sun∗State Key Laboratory of Pollution Control and Resource Reuse,School of Environment,Nanjing University,Nanjing210093,ChinaReceived22March2006;received in revised form17May2006;accepted18May2006Available online26May2006AbstractThe present study investigates the degradation of atrazine(2-chloro-4-(ethyl amino)-6-isopropyl amino-s-triazine)in aqueous solution by a developed new method,namely by means of a microwave-assisted electrodeless discharge mercury lamp(MW-EDML).An experimental design was conducted to assess the inﬂuence of various parameters:pH value,initial concentration,amount of EDML,initial volume and coexisted solvent.Atrazine was degraded completely by EDML in a relatively short time(i.e.t1/2=1.2min for10mg/l).Additionally,the identiﬁcation of main degradation products during atrazine degradation process was conducted by gas chromatography–mass spectrometry(GC–MS)and liquid chromatography–mass spectrometry(LC–MS).This study proposes the degradation mechanism including four possible pathways for atrazine degradation according to the degradation products.©2006Elsevier B.V.All rights reserved.Keywords:Atrazine;Microwave;Electrodeless discharge mercury lamp;Photodegradation;Pesticide1.IntroductionMW has been developed over than30years since in1975 Abu-Samraﬁrst applied MW oven in laboratory.It has become a very attractive tool in synthetic organic chemistry because of its great ability to accelerate chemical reactions with improved yields and selectivity[1].MW application is an activeﬁeld of research,so it is also greatly applied in environmental sci-ence as a more effective,easier,cheaper extraction technique compared to traditional methods.The major advantages of MW extraction are decreased extraction time,reduced solvent con-sumption,increased sample throughput[2].Application of MW in some other environmental researchﬁelds is still in progress [3,4].An original photochemical reactor consisting of an elec-trodeless discharge lamp(EDL)was introduced in detail[5].It was reported to be a prospective tool for photochemistry with good photochemical efﬁciency,simplicity and inexpensiveness by simultaneous application of UV and MW irradiation in exper-iment[6].However,the MW-EDL was not widely employed ∗Corresponding author.Tel.:+862583593372;fax:+862583707304.E-mail address:tanawu@(C.Sun).in decomposition of organic pollutants especially in pesticides [7,8].Atrazine(2-chloro-4-(ethylamino)-6-isopropylamino-s-tri-azine)was introduced in the1950s,and since then atrazine has become the most widely used herbicide in agricultural and forestry applications,with70,000–90,000tonnes applied annu-ally in the world.Atrazine has high effectiveness in inhibiting the growth of target weeds including variety of plants and some species of algae by interfering with the normal function of photosynthesis[9].In addition,atrazine has the properties of high leaching potential,persistence in soil,slow hydroly-sis,low vapor pressure,solubility in water and high toxicity to aquatic organisms and lower for mammals[10].Because of these properties,atrazine applied to cropland can be transported to groundwater by inﬁltration or to surface waters by water runoff[11].Atrazine is more frequently detected in ground water and surface water of many countries than any other herbicides [9,12].Atrazine persists under cool,dry conditions,in a sta-ble pH environment.For these reasons,numerous studies have been carried out on degradation of atrazine applying different methods such as advanced oxidation method[13],catalytic oxi-dation process[14]and microorganism removal[15]for objec-tive of resolving atrazine contamination and removing atrazine0304-3894/$–see front matter©2006Elsevier B.V.All rights reserved. doi:10.1016/j.jhazmat.2006.05.050188N.Ta et al./Journal of Hazardous Materials B138(2006)187–194from water system.Both advanced oxidation method and cat-alytic oxidation process show higher efﬁciency in removal of atrazine in a mild condition and have received increasing atten-tion.However,they are demanding preparation of catalyst and feasible regeneration of catalyst,thus,it is sometimes not desir-able.Additionally,atrazine is toxic for microorganisms and the triazine-ring itself is quite resistant to the microbial attack[16]. As a result,conventional biological remediation processes are not efﬁcient and unsuitable to remove higher concentration of atrazine from contaminated water rapidly.Therefore,all above methods are time costing and the application is restricted by limited conditions of the methods.Thus,until now,no com-pletely efﬁcient methods have been developed for remediation of atrazine-contaminated water.The degradation mechanisms and metabolic pathways of triazines have been also largely investi-gated[17,18],but the mechanisms of atrazine degradation still remain unclear and little information is available on the degra-dation mechanism of atrazine under MW-EDML irradiation, which serves as background data for environmental behavior of atrazine.A MW-EDML reactor was developed in our laboratory and was applied to remove higher concentration of atrazine with impressive degradation capability.Several factors affecting the degradation of atrazine,such as the initial concentration of atrazine,pH value,the initial solution volume,the amount of EDML and trace coexisted solvent were studied in detail.In present study,applying LC–MS and GC–MS to identiﬁcation of degradation products and according to the results of LC–MS and GC–MS,the possible degradation pathway and degradation products for atrazine are also predicted and proposed.It is also proved that MW-EDML is a very simple,economic,efﬁcient, environmentally friendly and prospective tool for degradation of atrazine.2.Materials and methods2.1.ChemicalsStandard atrazine(99.0%)was purchased from Supelco (Bellefonte,PA,USA),and HPLC grade solvents (dichloromethane and methanol)used in the analysis were purchased from Tedia(Fairﬁeld,OH,USA).Atrazine solution was prepared in methanol.Anhydrous sodium sulfate(ana-lytical grade)was purchased from Nanjing Chemical Factory. Phosphate buffer solution with concentration of0.02mol/l was prepared in distilled water(pH3.0,5.0,6.0,7.0,8.0,9.0).All chemicals were used as received.2.2.Methods2.2.1.MW experimentsAll MW degradation experiments was conducted in MW-EDML reactor,which consisted of a MW oven,Pyrex ves-sel,EDML,glass tube connector and water-cooling condenser (Fig.1).A domestic MW oven(Midea,PJ23C-SCI,China)was one of the important parts of this reactor,which was mod-iﬁed as follows:a hole was drilled in the upper ovenwall Fig.1.The microwave-assisted photochemistry reactor:(1)water-cooled con-denser;(2)aluminum tube(glass tube connector in it);(3)vessel;(4)magnetron;(5)glass tube;(6)microwave oven cavity;(7)electrodeless discharge mercury lamps(EDML).and an aluminum tube of the same diameter was attached to the hole in order to eliminate possible MW leaking.In the aluminum tube,a glass tube was attached connecting a water-cool condenser and a Pyrex vessel on its both sides. The EDML was placed into the vessel which was then put into the MW oven cavity.So,when the MW begins to work, the EDML is excited and causes UV–vis irradiation which is absorbed by the atrazine solution and induces the degra-dation of atrazine.The EDML was made of Pyrex with desired length,ﬁlled with argon and a few drops of mer-cury and as well as sealed under vacuum.The EDML lamp (10mm×50mm)has prominent emission bands at254,313, 365,405,436,546,577and579nm[19]and light intensity of 254–300nm is9–10mW/cm2for four EDML with good sta-bility more than800min.The MW power was adjusted to a maximal value(900W),which guaranteed continuous MW radi-ation.When the experiment was started,the vessel with atrazine aqueous solution and EDML was placed into the MW oven cavity and connected to the glass tube connector and the water-cooling condenser systems.After installation,the reactor began to work and the solution for measurement of atrazine was obtained in time.The basic degradation experiments were car-ried out with above mentioned MW-EDML reactor.All the processes and the results described below were performed under this reactor.2.2.2.HPLC analysis of atrazineThe degradation process followed a consecutive measure-ment of atrazine in time by a HPLC system(Agilent,USA, 1100Series high-performance liquid chromatography)equipped with Zobax Extend-C18HPLC column(150mm×4.6mm i.d.,5␮m,Agilent,USA),a diode array detector(DAD) and an auto sampler controlling under a Chemstation data acquisition system.The measurement was performed in a methanol/water(60:40,v/v)phase at aﬂow rate of1.0ml/min. The wavelength was set at220nm which is the maxi-mum absorption of atrazine and the column temperature was 30◦C.Retention time of atrazine was4.67min at the above conditions.N.Ta et al./Journal of Hazardous Materials B138(2006)187–1941892.2.3.SPE enrichment of degradation productsAccording to previous literature[11],the C18tube has a high efﬁciency on recovering atrazine and most of atrazine degra-dation products.In order to identify all degradation products of atrazine,the Supelclean ENVI TM-18solid phase extraction (SPE)tubes(Supelco,Bellefonte,PA,USA)were chosen for the enrichment of degradation products of atrazine.The SPE tubes were packed with1mg of silica gel bonded reversed phase parkings with average particle size at56.0␮m.Before the enrichment,the SPE tubes were preconditioned with10ml of methanol and then10ml of distilled water and stored at dis-tilled water until the enrichment procedure.The water solutions after degradation were trapped through the SPE tubes with aﬂow rate of5ml/min under vacuum pump.The SPE tubes enriched degradation products were eluted by5ml methanol twice and then the eluent was dried by adding anhydrous sodium sulfate and evaporated in an evaporator,then in a gentle stream of nitro-gen until the volume was less than1ml.2.2.4.Identiﬁcation of degradation products by LC–MSand GC–MSLC–MS and GC–MS are proved to be the appropriate and useful apparatus in the conﬁrmation of many organic pollu-tants and their degradation products,which are widely applied in environmental science.However,an unambiguous identiﬁca-tion of phototransformation products is often not readily possible because of the limitation of the apparatus.LC–MS–APCI is use-ful in detection of polar and thermally labile chemicals providing the molecular weight,but the information of molecular structure and inquiring laboratory system are unavailable or undesirable. GC–MS applies in nonpolar chemicals by providing the infor-mation of molecular structure following a relatively abundant inquiring laboratory system,but for some degree,GC is unde-sirable in polar organic pollutants.Therefore,the combination of LC–MS–APCI and GC–MS information might be more effec-tive in getting more information about degradation products.The identiﬁcation of atrazine and its degradation products wasﬁrst performed by LC–MS(ThermoQuestLCQ Duo,USA) with Beta Basic-C18HPLC column(150mm×2.1mm i.d., 5␮m,Finnigan,Thermo,USA).Theﬁnal extract(10␮l)from SPE enrichment was injected automatically into the LC–MS system.Theﬂow rate was0.2ml/min.The other LC conditions were described in Section2.2.2.MS conditions were as follows: the MS was equipped with atmospheric pressure chemical ion-ization and electrospray ionization interface(APCI/ESI).The APCI interface was selected and the capillary temperature was set to150◦C with a voltage of10V.The spectra were acquired in the positive scan mode,over the m/z range40–500at1scan/s. The discharge current was5␮A and the sheath gasﬂow rate was 60AU.The identiﬁcation of atrazine and its degradation products was also conducted by a Finnigan Thermo Trace gas chro-matography interfaced with a Polaris Q ion trap mass spectrom-eter(GC–MS,Finnigan Thermo,USA).The instrument was controlled by the Xcalibur software from Finnigan.Theﬁnal extracts(1.0␮l)were automatically injected into a5%equiva-lent polysilphenylene-siloxane GC column(DB-5fused-silica capillary column,30m×0.25mm i.d.,0.25␮mﬁlm thickness) with splitless mode.The oven temperature was programmed as follows:the initial temperature was60◦C,then60–200◦C at ramp rate of10◦C/min hold2min,to240◦C at4◦C/min, to280◦C at10◦C/min holds2min.The MS conditions of the analysis were as follows:injector temperature and transfer line temperature was set at250and200◦C,respectively.The carrier gas was helium withﬂow rate of1.5ml/min at constantﬂow with vacuum compensation.The mass spectra were scanned from40 to650␮m at0.4scan/s.The MS was operated with a70-eV electron impact(EI)mode with positive ion mode.3.Results and discussion3.1.The factors affecting degradation of atrazine3.1.1.Effect of initial concentration of atrazineThe effect of initial concentration of atrazine was exam-ined with different concentrations at5,10,20and50mg/l (Fig.2).As shown in Fig.2,with the increasing of initial con-centration of atrazine,the degradation rates were decreased. It indicates that initial concentration greatly affects the degra-dation rate of atrazine.When initial concentration was5mg/l, the degradation rate constant was0.89min−1,and atrazine was degraded completely within6min.However,when the initial concentration was increased to50mg/l,degradation rate con-stant was decreased to0.1459min−1,complete degradation of which needed30min.It might be the reason that degradation amount of atrazine is affected by light intensity of UV–vis irradi-ation.Therefore,under invariable light intensity,the degradation rate of atrazine decreases when the concentration of atrazine in the aqueous solution is increased.The degradation followed a ﬁrst order rate equation,which is conﬁrmed by the evidence of a straight line relationship of logarithmic atrazine concentra-tion versus irradiation time(r>0.92),this is coherent with the literature[20].3.1.2.Effect of initial volume of atrazineIn order to estimate the effect of solution volume,degradation of atrazine with a series of different volumes was carriedout. Fig.2.Effect of initial concentration of atrazine:5mg/l( ),10mg/l( ),20mg/l ( )and50mg/l( );solution volume of atrazine was50ml(pH6.3,under one EDML irradiation).190N.Ta et al./Journal of Hazardous Materials B138(2006)187–194Fig.3.Effect of initial volume of atrazine:the initial volume of atrazine was 25ml ( ),50ml ( ),75ml ( )and 100ml (*);the concentration of atrazine was 10mg/l (pH 6.3,without buffered,under one EDML irradiation).Fig.3shows the experimental result when the same concentra-tion of atrazine (10mg/l)was conducted with different volumes at 25,50,75and 100ml.It was obvious that the solution volume has a great inﬂuence on atrazine degradation.The experiment with smaller volumes showed higher degradation rate than that of larger one.It might be the reason that degradation amount of atrazine is inﬂuenced by light intensity of UV–vis irradiation.With increasing the volume of arazine solution,the amount of atrazine increased but the light intensity of UV–vis irradiation not changed,as a result,degradation rate of atrazine decreased.3.1.3.Effect of pH valueThe effect of pH value on atrazine degradation was investi-gated by ranging the pH value of aqueous solution of atrazine from pH 3to 9(Fig.4).As inferred from Fig.4,atrazine degrada-tion is also strongly dependent on pH.A signiﬁcant enhancement of the degradation is experienced when increasing the pH value of aqueous solution of paring the half-lives of atrazine at different pH values (not shown),it is concluded that degradation is slowed down in an acidic medium;on the con-trary,the degradation of atrazine tends to be most efﬁcient at the highest pH value,which might be a result of hydroxide ioncon-Fig.4.Effect of pH value:pH 3( ),pH 5( ),pH 6( ),pH 7(×),pH 8(*)and pH 9(♦);atrazine concentration was 50mg/l (phosphate buffer solution,under one EDMLirradiation).Fig.5.Effect of EDML:0( ),1( ),2( )and 3(*);atrazine concentration was 50mg/l (50ml,pH 6.3,not buffered,under various amounts ofEDML).Fig.6.Effect of solvent:no solvent ( ),methanol ( )and acetone ( );atrazine concentration was 10mg/l (50ml,pH 6.3,not buffered,under one EDML irra-diation).centration.The same behavior was reported by other literature [16].3.1.4.Effect of EDMLThe degradation experiments were conducted in various amount of EDML including the blank experiment.Following the degradation processes under different amounts of EDML which lead to a diagram,it is shown in Fig.5.The effect of EDML on degradation of atrazine is apparent in Fig.5.It can beconcludedFig.7.Evolution of the concentration of atrazine and its ﬁrst degradation prod-ucts during microwave-assisted photolysis:AT ( ),HAET ( ),HIET ( ),CDT (×),CAIT (*).The unclear parts of the ﬁgure have been enlarged and is shown in inset.N.Ta et al./Journal of Hazardous Materials B138(2006)187–194191that there is a relationship between the amounts of EDML and the degradation efﬁciency of atrazine.When increasing the amount of EDML,the degradation rates apparently increase. It is worth pointing out that in blank experiment(without EDML),no degradation of atrazine was observed although the MW irradiation was still applied.This evidence implies that the existence of EDML can produce UV–vis irradiation which can degrade the atrazine,nevertheless the MW irradiation cannot degrade the atrazine.Additionally,the degradation efﬁciency strongly depends on the light intensity of EDML irradiated UV–vis which is correlated to the amount of EDML.3.1.5.Effect of coexisted solventTo assess a small volume of solvent(less than1vol.%)in the degradation process of atrazine,the experiment was conducted in an aqueous solution and with a small volume of methanol and acetone(Fig.6).It was observed that a small volume of methanol and acetone slowed down the degradation rateof Fig.8.Degradation pathways of atrazine under MW-EDML:(1)dechlorination–hydroxylation;(2)dealkylation;(3)alkylic-oxidation;(4)delamination–hydroxylation process.192N.Ta et al./Journal of Hazardous Materials B138(2006)187–194atrazine,respectively.The effect on the degradation of atrazine was notable at the beginning of degradation,but the solvents in the aqueous solution of atrazine were not apparent at the end of the experiment.It can be explained by the different characters of methanol and acetone.Known as a photosensitizer,acetone will compete with atrazine for absorption of UV–vis light.More-over,as a quencher of radicals,methanol will trap the radicals and slow down the consequent degradation of atrazine.During the experiment,the solvent in the solution is volatilized gradu-ally due to thermo-effect of MW.3.2.Degradation products and degradation mechanismIn the present work,we focused mainly on the mechanism of atrazine degradation with particular care in the identiﬁcation of degradation products.The degradation of10mg/l atrazine solu-tion was investigated and the concentrations ofﬁrst degradation products were evaluated as shown in Fig.7.The experiment was conducted20min.As can be seen in Fig.7,atrazine was degraded quickly and completely degraded in8min,and simul-taneously some degradation products were formed and reached gradually the maximum,then they also began to degrade.Among the degradation products,one main degradation product was accumulated and its concentration was much higher than the other degradation products.According to the analysis of LC–MS and GC–MS,the main degradation product is HIET.From Fig.7, it is observed that HIET is degraded slowly while the degra-dation time is increased.It indicates that formation of HIET (dechlorination–hydroxylation mechanism)is one of the main degradation mechanisms of atrazine in an aqueous solution by UV–vis irradiation of MW-EDML,which is in accordance with the previous studies[14,21].The formation of HIET could result either from a homolytic cleavage of the C–Cl bond followed by an electron transfer from the carbon to the chlorine radicals pro-cessed by the carbocation reaction with water,or the heterolytic cleavage of the excited state atrazine molecule which is favored by polar solvents such as water[18].In addition,some other degradation products were formed during20min degradation process.According to the result of GC–MS and LC–MS analysis,they were found to be the dealky-lation products(CDT and CEAT)and alkylic-oxidation product (CAAT).However,from the evaluation of their concentration (Fig.8),it is obvious that their formation is minor and they are also degraded under increased degradation time.It indicates that the dealkylation and alkylic-oxidation of atrazine are two other mechanisms for atrazine degradation.Table1Structures,retention time and abbreviation of atrazine and degradationproductsm/z or(m+1)Retention time Detected Abbreviation Compounds X R1R223010.26LC–MS CAIT2-Chloro-4-acetamindo-6-(isopropylamino)-s-triazineCl NHCOCH3NHCH(CH3)22269.60LC–MS,GC–MS M-HAITM2-Hydroxy-4-acetamindo-6-(isopropylamino)-s-triazineOCH3NHCOCH3NHCH(CH3)2216 6.75LC–MS,GC–MS AT2-Chloro-4-(isopropylamino)-6-(ethylamino)-s-triazine(atrazine)Cl NHC2H5NHCH(CH3)2212 6.25LC–MS,HAITM2-Hydroxy-4-acetamindo-6-(isopropylamino)-s-triazineOH NHCOCH3NHCH(CH3)22127.32LC–MS,HDAT2-Hydroxy-4,6-diacetamindo-s-triazine OH NHCOCH3NHCOCH3 2128.63LC–MS,GC–MS M-HIET2-Hydroxy-4-(isopropylamino)-6-(ethylamino)-s-triazineOCH3NHC2H5NHCH(CH3)2198 2.55LC–MS,GC–MS HIET2-Hydroxy-4-(isopropylamino)-6-(ethylamino)-s-triazineOH NHC2H5NHCH(CH3)2198 3.59LC–MS,GC–MS HAET2-Hydroxy-4-acetamido-6-(ethylamino)-s-triazineOH NHCOCH3NHC2H5198 5.30LC–MS CDVT2-Chloro-4,6-(divinylamino)-s-triazine Cl NHC2H4NHC2H4 198 5.71LC–MS,GC–MS M-HDT2-Hydroxy-4,6-(diethylamino)-s-triazine OCH3NHC2H5NHC2H5 182 4.46LC–MS,GC–MS HVET2-Hydroxy-4-(vinylamino)-6-(ethylamino)-s-triazineOH NHC2H4NHC2H5174 3.59LC–MS,GC–MS CEAT2-Chloro-4-(ethylamino)-6-amino-s-triazine Cl NHC2H5NH2154 2.61LC–MS,GC–MS HV AT2-Hydroxy-4-(vinylamino)-6-amino-s-triazineOH NHC2H4NH2154GC–MS DVT2,6-Dihydroxy-4-(vinylamino)-s-triazine OH NHC2H4OH187GC–MS CAAT2-Chloro-4-acetamido-6-amino-s-triazine Cl NH2NHC2H5 145GC–MS CDT2-Chloro-4,6-diamino-s-triazine Cl NH2NH2N.Ta et al./Journal of Hazardous Materials B138(2006)187–194193Fig.9.Scissile bonds in atrazine molecular under MW-EDML.In order to assess all the available degradation products dur-ing atrazine degradation,the same concentration of atrazine with longer degradation time(40and120min)and higher concentra-tion of atrazine with longer degradation time(50mg/l,40and 120min)in the degradation process were conducted.All the identiﬁed degradation products and their retention times,names, formulae and structures are presented in Table1.Furthermore, according to Table1,the possible degradation pathways are pro-posed in Fig.8.The degradation of atrazine in MW-EDML in an aqueous solution is a complicated process.Nevertheless,it still follows certain patterns of mechanism.According to previous literature [22],we suggest that the MW-EDML irradiation will lead to the promotion of atrazine to their excited singlet states,then may transit to the triplet states and then undergo the three possible processes,namely,homolysis,heterolysis and photoionization. According to the structure of atrazine,we suggest that there are several bonds(Fig.9)which are easy to cleave when they get enough energy from UV–vis irradiation during MW-EDML degradation process.The bond␣is the easiest to be scissile as compared to any other bonds.The cleavage of bond␣lead to a dechlorination–hydroxylation process(the chlorine atom was substituted by a hydroxyl group):in this process,it is esti-mated that the chlorine atom which is connected to the carbon atom on the heterocyclic ring might cause a cleavage due to its higher polarity and is substituted by hydroxyl group at the same time.While the dechlorination occurs,the hydroxylation hap-pens simultaneously.Consequentially,the degradation product HIET is being formed.Additionally,the b,c,f and g bonds might also cleave easily and form dealkylation(alkylic lateral chain cleavage) degradation products including demethylation,deethylation and deisopropylation which are CDT,CAAT and CEAT identiﬁed by GC–MS and LC–MS,respectively.There is no evidence from GC–MS or LC–MS that the g bond is cleaved during the degradation process.Therefore,it is estimated that the order of those bonds cleavage from easy to difﬁcult goes as follows: b>c>f>g.This is supported by the previous work showing that deethylation is easier than deisopropylation[23].We suggest that the cleavage of those bonds might result in the formation of some neutral molecular such as alkenes or alkyl radicals.In addition,an attack of the hydroxyl group on N-adjacent carbon atom of bonds b and c might result in an alkylic-oxidation (alkylamino lateral chain oxidation)process which is proved by the identiﬁcation of CAIT,HAITM,HDAT and HAET.It is estimated that the abstraction of the hydrogen atom might occur in the case of hydroxyl radical’s attacks on N-adjacent carbon atom.The observation of HVET might be explained by this mechanism.If only amino group remained on the lateral chain of hetero-cyclic ring after complete dealkylation,bond d might cleave and cause the deamination–hydroxylation process(the amino group is substituted by a hydroxyl group).It should be pointed out that only after the dealkylation,the deamination–hydroxylation pro-cess is likely to occur.The cleavage of bond d and attack of the hydroxyl radicals on the carbon atom of heterocyclic ring hap-pen simultaneously.This can be supported by the observation of DVT.It may be pointed out that in the second step or ulterior steps, the above four degradation mechanisms may compete with one another,thus,the mixture of lateral chain losing,lateral chain oxidizing and hydrolyzing products are being formed.In general,the common processes of degradation of atrazine are as follows:partial or complete loss of lateral chains;oxida-tion of lateral chains;substitution hydroxyl group for chlorine or amino group rather than opening the heteroatom ring.The degra-dation process mayﬁnally lead to the formation of ultimate pro-duction of cyanuric acid(2,4,6-trihydroxy-1,3,5-triazine,CA) rather than causing the complete mineralization which is often observed for other chemicals.However,CA is not detected in our experiment,but it is eventually formed when a sufﬁcient intensity of irradiation is provided with an extended time.It suggests that the heterocyclic ring has a much higher stability to decompose under the UV–vis light intensity irradiated by MW-EDML.As far as we know,the complete mineralization has not been reported in any other previous literature of photodegrada-tion and biodegradation processes.Cyanuric acid was treated by Fenton Reagent and photocatalyst for100h,but no meaningful disappearance was observed[17].Fortunately,it was reported that cyanuric acid had a low toxicity[17].Therefore,the MW-EDML process shows a very efﬁcient means for detoxiﬁcation of atrazine.4.ConclusionPhotodegradation of atrazine in an aqueous solution by MW-EDML was investigated in this study.The MW-EDML is proved to be a very simple,economic,efﬁcient,prospective and envi-ronmentally friendly tool for detoxiﬁcation of atrazine.The initial pH value,initial concentration of atrazine,volume of solution,amount of EDML and coexistent solvent are all the factors strongly affecting the atrazine degradation.In addition, the main degradation pathways proposed include the four ways: dealkylation,dechlorination–hydroxylation,alkylic-oxidation, and delamination–hydroxylation.In general,the most com-monly degraded process of atrazine loses the lateral chains partially or completely,oxidizes and hydroxylates in the lateral chains rather than opens the heteroatom ring. AcknowledgmentsThis study was supported by Chinese national programs for high technology research and development863projects(No. 2002AA601011-03).。

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Degradation of nitrobenzene using titania photocatalyst co-doped with nitrogen and cerium under visible light illuminationXiang-Zhong Shen, a, , Zhi-Cheng Liu a, Shan-Mei Xie a and Jun Guo aa Department of Chemistry and Materials Science, Hunan Institute of the Humanities and Science and Technology, Loudi 417000, ChinaReceived 5 March 2008;revised 1 June 2008;accepted 3 June 2008.Available online 8 June 2008.AbstractA type of nitrogen and cerium co-doped titania photocatalyst, which could degrade nitrobenzene under visible light irradiation, was prepared by thesol–gel route. Titanium isopropoxide, ammonium nitrate, and cerium nitrate were used as the sources of titanium, nitrogen, and cerium, respectively. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis diffusive reflectance spectroscopy (DRS), scanning electron microscopy (SEM), and N2 adsorption–desorption isotherm were employed to characterize theas-prepared photocatalyst. The degradation of nitrobenzene under visible light illumination was taken as probe reaction to evaluate the photoactivity of theco-doped photocatalyst. The commercial TiO2 photocatalyst (Degussa P25), which was thought as a high active photocatalyst, was chosen as standard photocatalyst to contrast the photoactivity of the nitrogen and cerium co-doped titania photocatalyst. The results showed that the photocatalyticperformance of the nitrogen and cerium co-doped titania was related withthe synergistic effects of the nitrogen and cerium co-doping.Nitrobenzene degradation; Nitrogen; Cerium; Co-doped; TitaniaThe modification to titania by co-doping was an effective method and the cooperate action of the co-doping was able to improve the photocatalyticreported that the cooperative action of co-doping ofNi co-doped photocatalyst using the modified solP co-doped titania photocatalyst extending spectral response to the visible light region. They proved that coand fluorine co-doped titania photocatalyst showing high photocatalyticdemonstrated that the observed high photocatalytic activity of the samples could be ascribed to a synergetic effect of nitrogen and fluorine co-doping. Ling et al. [24] prepared the B and N co-doped TiO2 nanopowders using boric acid and ammonium fluoride as the precursors of boron and nitrogen. They proved that the synergistic effect of B and N co-doping was responsible for improving the photocatalytic performance. These reports unequivocally indicated that modification to titania by co-doping was an effective method for increasing the photocatalytic activity.However, there were few reports on the co-doped photocatalyst with nitrogen and cerium. In the present work, the nitrogen and cerium co-doped titania photocatalyst with high photocatalytic performance under visible light was prepared using the sol–gel method. The prepared samples were characterized by XRD, XPS,DRS, SEM, and N2 adsorption–desorption isotherm. The photocatalytic performance was evaluated by means of the degradation for nitrobenzene under visible light illumination.2. Experimental2.1. Photocatalyst preparationIn this study titanium isopropoxide was chemically pure and others were analytically pure. All chemicals were used without any further purification. Water used was deionized water.The nitrogen and cerium co-doped titania was synthesized by the following procedure. A certain amount of ammonium nitrate and cerium nitrate was dissolved in the mixture of 10 mL of deionized water, 10 mL of glacial acetic acid, and 80 mL of ethanol at room temperature to gain solution A. Titanium isopropoxide (28.6 g, 0.1 mol) was dissolved in 100 mL of absolute ethanol to form solution B. Then, the solution B was added drop-wise into the solution A within 60 min under vigorous stirring, followed by stirring for 2 h. The resultingsol was aged for 48 h at room temperature and was dried for 12 h at 80 °C. Thus, the xerogel was to be obtained. The resultant xerogel was milled and annealed at different temperature for 3 h to remove the residual organic compounds to prepare the nitrogen and cerium co-doped photocatalyst. The sample was labeled as N(x)Ce(y)TiO2-t, where x and y represented the mole ratios of ammonium nitrate to titanium isopropoxide and cerium nitrate to titanium isopropoxide, respectively, and t denoted the corresponding temperature of calcination (°C).2.2. Photocatalyst characterizationThe XRD patterns of samples were recorded by means of a D/max-RB X-ray diffractometer equipped with Cu Kα radiation (λ = 0.15406 nm) in a 2θ range of 20–70°. The scanning speed was 4°/min. The standard diffraction charts of anatase and rutile were used to compare with the obtaining XRD patterns. Crystallite sizes of the samples were estimated by the Scherrer equation and the lattice constants were calculated using full profile structure refinement of XRD data. The X-ray photoelectron spectra of the co-doped photocatalyst were measured by a Thermo Escalab250 X-ray photoelectron spectroscope equipped with Al Kα excitation. The binding energies for N 1s, Ti 2p, and Ce 3d were calibrated with respect to the signal for adventitious carbon (binding energy = 284.6 eV). The surface electronic states and the chemical states were analyzed using the binding energies. The UV–vis diffusive reflectance absorption spectra of samples were recorded on a Shimadzu (Japan) UV–Vis 2100S spectrophotometer with an integrating sphere attachment. The scanning range was between 200 nm and 800 nm. BaSO4 was used as a reference. The structural morphology of sample was observed by a microscope (Philips XL 30 CP). The particle size was estimated approximately by SEM photograph. Specific surface area was determined by the BET method based N2 adsorption on a Autosorb-1 at 77 K. Prior to adsorptionmeasurement, the sample was degassed in an evacuation chamber for 12 h at 423 K.2.3. Photocatalytic activity testNitrobenzene was used as a model organic pollutant. The degradation of nitrobenzene was taken as a model reaction to assess the photocatalytic performance of the nitrogen and cerium co-doped titania photocatalyst. In all the studies, the suspension containing 200 mL of 50 mg/L nitrobenzene aqueous solution and 0.20 g of photocatalyst was loaded in a 500 mL of homemade quartz vessel beaker and was magnetically stirred. A 300 W xenon lamp provided the light source and a 400 nm glass filter was used to remove the UV light. The degradation reaction was carried out under visible light irradiation and the reaction temperature was maintained at 30.0 °C. After the mixture was ultrasonicated for 10 min and stirred for 60 min in the dark to achieve the adsorption equilibrium, the xenon lamp was turned on. The decomposition experiment was carried out for 4 h. Prior to irradiation and after irradiation of 4 h, 5 mL of sample was taken out and centrifugated for determining the nitrobenzene concentration, from which the nitrobenzene conversion was calculated.3. Results and discussion3.1. XRD spectra of samplesFig. 1 shows the XRD patterns of the different samples. From Fig. 1, one could observe a characteristic peak (2θ = 27.4°) assigned to rutile (1 1 0) for the sample TiO2-600. However, one could not see the characteristic peak assigned to rutile for the other samples. One could conclude that the sample TiO2-600 existed in the states of both anatase and rutile, and that the other samples existed only in anatase phase. Obviously, the XRD patterns revealed that the doping could retard the transformation from anatase to rutile atFull-size image (21K)Fig. 1. XRD patterns of different samples: (a) N(0.02)Ce(0.01)TiO2-400, (b)N(0.02)Ce(0.01)TiO2-500, (c) N(0.02)Ce(0.01)TiO2-600, (d) N(0.02)TiO2-500, (e) Ce(0.01)TiO2-500, (f) TiO2-500, and (g) TiO2-600.According to Fig. 1, the width of the (1 0 1) plane diffraction peak of anatase (2θ = 25.3°) become narrower for the nitrogen and cerium co-doped titania with the annealing temperature increasing. Based on the Scherrer equation, one could conclude that the average particle size increased when increasing the calcination temperature. Moreover, the average grain sizes of the samples were shown in Table 1 and were 22.9 nm, 9.2 nm, 9.6 nm, and 10.2 nm for TiO2-500, N(0.02)Ce(0.01)TiO2-400, N(0.02)Ce(0.01)TiO2-500, andN(0.02)Ce(0.01)TiO2-600, respectively. Apparently, the annealing temperature had an effect on the grain size of the nitrogen and cerium co-doped titania photocatalyst.Table 1.Crystal size and surface area of samples3.2. XPS spectra of the nitrogen and cerium co-doped TiO The XPSFull-size image (13K)Fig. 2. XPS spectra of the typical sample N(0.02)Ce(0.01)TiO2-500 for N 1s.Full-size image (13K)Fig. 3. XPS spectra of the typical sample N(0.02)Ce(0.01)TiO2-500 for Ti 2p.Full-size image (12K)Fig. 4. XPS spectra of the typical sample N(0.02)Ce(0.01)TiO2-500 for Ce 3d.Combined with the XRD analysis, one could deduce that the doping nitrogen atoms were weaved into titania crystals, and that the doping cerium atoms presented in the forms of Ce2O3 and were distributed on the surface of titania.3.3. UV–vis DRS spectra of samplesFig. 5 shows the optical absorption spectra of the different samples. The samples N(0.02)TiO2-500 and N(0.02)Ce(0.01)TiO2-500 absorbed observably in the visible region from 400 nm to 800 nm wavelengths. However, the samples Ce(0.01)TiO2-500 and TiO2-500 hardly absorbed visible light. The red shift of the absorption edge demonstrated a decrease in the band gap energy. According to the results from XRD and XPS,the doping nitrogen atoms were weaved into titania crystals and led to the modification of the electronic structure around the conduction band edge of TiO2 because of the substitution of the lattice oxygen by nitrogen during the TiO2 nitridation, whereas the doping cerium atoms presented in the forms of Ce2O3 and were distributed on the surface of titania. Therefore, N doping led to the band gap narrowing [17]. However, Ce doping did not.Full-size image (7K)Fig. 5. Diffuse reflectance absorption spectra of the different samples: (a)TiO2-500, (b) Ce(0.01)TiO2-500, (c) N(0.02)TiO2-500, and (d)N(0.02)Ce(0.01)TiO2-500.Furthermore, the intercept on the wavelength axis for a tangent drawn on DRS spectra was used to determine the onsets of absorption edge, which were 393.1 nm for TiO2-500 and 560.7 nm for the sample N(0.02)Ce(0.01)TiO2-500.3.4. SEM photograph of N–Ce co-doped TiO2 photocatalystFig. 6 shows SEM photograph of the typical sample N(0.02)Ce(0.01)TiO2-500. From the image, the sample N(0.02)Ce(0.01)TiO2-500 existed approximately in the form of spherical particle and presented the porous structures. According to the statistical estimation, the average size was about 10.3 nm, which was in accordance with the value determined by XRD (9.6 nm). In addition, other samples investigated were so from the SEM images (not shown), too.Full-size image (27K)Fig. 6. SEM pattern of the typical sample N(0.02)Ce(0.01)TiO2-500.3.5. BET surface areaTable 1 shows the Brunauer–Emmett–Teller (BET) surface areas of different samples calculated from the linear part of the BET plots. The surface areas were 29.8 m2/g, 89.6 m2/g, 151.9 m2/g, 144.5 m2/g, and 132.7 m2/g for the samples TiO2-500, Ce(0.01)TiO2-500, N(0.02)Ce(0.01)TiO2-400,N(0.02)Ce(0.01)TiO2-500, and N(0.02)Ce(0.01)TiO2-600, respectively. There was no doubt that co-doping led to the increase of BET surface area. In addition, the annealing temperature had an effect on the surface area of the nitrogen and cerium co-doped photocatalyst. As is well known, the photocatalytic reaction occurs on the surface and the surface area of photocatalyst influences the photocatalytic rate.3.6. Photocatalytic performanceThe adsorption of target pollutant over photocatalyst is the prerequisite of photocatalysis. Table 3 shows the concentrations of nitrobenzene at the adsorption equilibrium after 60 min in the dark over different photocatalysts. Obviously, it could be seen that the adsorption of nitrobenzene over different photocatalysts was influenced by the annealing temperatures and the component, and that the sample N(0.02)Ce(0.01)TiO2-400 adsorbed the most amount of nitrobenzene at the adsorption equilibrium among these samples. Fig. 7 shows the nitrobenzene conversion within 4 h under visible illumination over the different samples including P25, N(0.02)Ce(0.01)TiO2-500,N(0.02)TiO2-500, Ce(0.01)TiO2-500, and TiO2-500. Obviously, the samplesP25, N(0.02)Ce(0.01)TiO2-500, and N(0.02)TiO2-500 exhibited photocatalytic activity under visible light irradiation, whereas the samples Ce(0.01)TiO2-500 or TiO2-500 hardly degraded nitrobenzene. The results were in agreement with the outcome from the DRS analysis. According to Fig. 7, the photocatalytic activity of N(0.02)Ce(0.01)TiO2-500 was superior to that of N(0.02)TiO2-500, indicating that Ce2O3 distributed on the surface of photocatalyst doped with N could further improve the photocatalytic performance. It could be observed that the photoactivity of N(0.02)Ce(0.01)TiO2-500 exceeded that of P25. Compared with P25, there was an increase of 175% in photoactivity for the decomposing nitrobenzene under visible light for the sample N(0.02)Ce(0.01)TiO2-500.Table 3.The concentrations of nitrobenzene at the adsorption equilibrium after 60 min in the dark over different photocatalystsFig. 7. The nitrobenzene conversion within 4 h under visible illumination over the different samples: (a) P25, (b) N(0.02)Ce(0.01)TiO2-500, (c)N(0.02)TiO2-500, (d) Ce(0.01)TiO2-500, and (e) TiO2-500.Fig. 8 shows the nitrobenzene conversion within 4 h under visible illumination over the nitrogen and cerium co-doped titania samples with the different annealing temperatures and with the different component, includingN(0.02)Ce(0.01)TiO2-400, N(0.02)Ce(0.01)TiO2-450,N(0.02)Ce(0.01)TiO2-500, N(0.02)Ce(0.01)TiO2-550,N(0.02)Ce(0.01)TiO2-600, N(0.01)Ce(0.01)TiO2-500,N(0.015)Ce(0.01)TiO2-500, N(0.025)Ce(0.01)TiO2-500,N(0.02)Ce(0.005)TiO2-500, and N(0.02)Ce(0.02)TiO2-500. All the nitrogen and cerium co-doped titania samples showed photocatalytic activity under visible light irradiation. Compared with the nitrobenzene conversions over these samples, one could deduce that the photoactivity of the nitrogen and cerium co-doped titania photocatalyst was related to the annealing temperatures, and that the component of photocatalyst influenced the photoactivity. Among these samples, N(0.02)Ce(0.01)TiO2-500 owned the best photocatalytic performance for the nitrobenzene degradation within 4 h. It has been widely accepted that many factors have effects on the photoactivity of photocatalyst and these factors are closely related to each other [19], [32], [33] and [34]. Therefore, it was easy to understand that the sampleN(0.02)Ce(0.01)TiO2-500 exhibited the highest photocatalytic performance for nitrobenzene decomposition under visible light illumination.Full-size image (34K)Fig. 8. The nitrobenzene conversion within 4 h under visible illumination over the N–Ce co-doped titania samples with the different annealing temperatures and with the different component: (a) N(0.02)Ce(0.01)TiO2-400, (b) N(0.02)Ce(0.01)TiO2-450, (c) N(0.02)Ce(0.01)TiO2-500, (d)N(0.02)Ce(0.01)TiO2-550, (e) N(0.02)Ce(0.01)TiO2-600, (f)N(0.02)Ce(0.005)TiO2-500, (g) N(0.02)Ce(0.02)TiO2-500, (h)N(0.01)Ce(0.01)TiO2-500, and (i) N(0.025)Ce(0.01)TiO2-500.In order to test the stability of the nitrogen and cerium co-doped titania photocatalyst, six cycles of photocatalytic experiments were done using the sample N(0.02)Ce(0.01)TiO2-500 under visible irradiation. The photoactivity was found not to decrease, demonstrating that the as-prepared titania photocatalyst co-doped with nitrogen and cerium was stable.4. ConclusionsThe nitrogen and cerium co-doped titania photocatalyst was prepared through the sol–gel route. The as-prepared photocatalyst could adsorb the visible light and showed high photoactivity in the visible region because of the band gap narrowing. Nitrogen atoms were incorporated into the crystal lattice of titania and nitrogen doping destroyed locally the crystal structure, resulting in the response to the visible light. Cerium atoms existed in the state of Ce2O3 and were dispersed on the surface of titania, suppressing the recombination of electron–hole pairs and increasing the photoactivity. The as-prepared titania photocatalyst presented approximately the spherical shape and owned the porous surface. The average crystal size and the surface area correlated with the calcination temperature. The catalytic performance was influenced by the annealing temperature and the component of photocatalyst. The cooperative effect of the nitrogen and cerium co-doping improved the photocatalyticactivity. 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