径向流吸附器吸附穿透曲线的计算

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吸附动力学和热力学各模型公式及特点

吸附动力学和热力学各模型公式及特点1. Langmuir模型：Langmuir模型是最常用的吸附动力学方程之一，它假设吸附物分子只能以单层方式吸附在吸附剂表面。

该模型的方程表示为：dθ/dt = k_ads * (θ_max - θ) * P其中，dθ/dt表示单位时间内吸附量的增加速率，θ表示已吸附的物质分数，θ_max是最大吸附容量，P是气体或溶液中的吸附物质分压或浓度，k_ads是吸附速率常数。

2. Freundlich模型：Freundlich模型是一个经验模型，适用于多层吸附过程。

该模型的方程表示为：q=k_f*C^(1/n)其中，q表示单位质量的吸附物质的吸附量，C是气体或溶液中的吸附物质浓度，k_f和n是实验参数。

3. Temkin模型：Temkin模型假设吸附位点之间存在相互作用，并且随着吸附量的增加，吸附能力会降低。

该模型的方程表示为：q = K * ln(A * P)其中，q表示单位质量的吸附物质的吸附量，P是吸附物质的分压或浓度，K和A是实验参数。

- Langmuir模型适用于单层吸附过程，Freundlich模型适用于多层吸附过程，而Temkin模型考虑了吸附位点之间的相互作用。

- Langmuir模型假设吸附过程是可逆的，而Freundlich模型和Temkin模型则没有这个假设。

-吸附动力学模型通常基于实验数据拟合得出，因此需要大量的实验数据支持。

-吸附动力学模型常用于工业催化剂和废水处理等领域，用于优化吸附过程和预测吸附性能。

吸附热力学模型：1. Gibbs吸附等温方程：Gibbs吸附等温方程描述了吸附过程中的吸附热效应，即吸附热与吸附度的关系。

方程表示为：ΔG = -RTlnK = -ΔH + TΔS其中，ΔG是自由能变化，ΔH是焓变化，T是温度，R是气体常数，K是吸附平衡常数，ΔS是熵变化。

2. Dubinin-Radushkevich方程：Dubinin-Radushkevich方程适用于描述吸附剂对非特异性吸附的情况。

10第三章第五节移动床吸附过程的计算

第五节移动床吸附过程的计算在移动床吸附器的吸附操作中，吸附剂固体和气体混合物均以恒定速度连续流动，它们在床层任一截面上的浓度都在不断地变化，和气液在吸收塔内的吸收相类似。

移动床吸附过程的计算主要是吸附器直径、吸附段高度和吸附剂用量的计算。

我们可以仿照吸收塔的计算来处理问题，同时由于我们所进行的是低浓度气态污染物的吸附处理，可以按照等温过程对待。

为了简化计算，只讨论一个组分的吸附过程。

一、移动床吸附器直径的计算移动床吸附器主体一般为园柱形设备，和吸收塔计算塔径的公式相同： (3-53) 式中 D ——设备直径，m ；V ——混合气体流量，m 3/h ；u ——空塔气速，m/s 。

与吸收计算一样，在吸附设计中，一般来说混合气体流量是已知的，计算塔径的关键是确定空塔气速u 。

一般移动床中的空塔气速都低于临界流化气速。

球形颗粒的移动吸附床临界流化气速可由下式求得： (3-54) 式中 u mf ——临界流化气速，m/s ；μV ——气体粘度，Pa ·s ；ρV ——气体密度，kg/m 3；d p ——固体颗粒平均直径，m ；R emf ——临界流化速度时的雷诺准数，由下式求得：式中 A T ——阿基米德准数，由下式求取：式中 ρs ——吸附剂颗粒密度，kg/m 3。

若吸附剂是由不同大小的颗粒组成，则其平均直径应按下式计算：式中 x i ——颗粒各筛分的质量分率，%；d pi ——颗粒各筛分的平均直径，m ； u V D π4=v p V emf mf d R u ρμ=5.022.51400T T emf A A R +=)(23v s v v p T g d A ρρμρ-=∑==n i pi i p d x d 11d 1、d 2——上下筛目尺寸，m 。

计算出临界流化气速后，再乘以0.6～0.8，即为空塔气速u ，再代入（3-35）式，求出塔径D 。

二、移动床吸附器吸附剂用量的计算（一）物料衡算与操作线方程与吸收操作相类似，只是以固体吸附剂代替液体吸收剂。

（完整版）N2吸脱附曲线说明

（完整版）N2吸脱附曲线说明关于氮气等温吸脱附计算比表面积、孔径分布的若干说明我们拿到的数据，只有吸脱附曲线是真实的，比表面积、孔径分布、孔容之类的都是带有主观人为色彩的数据。

经常听到有同学说去做个BET，其实做的不是BET，是氮气等温吸脱附曲线，BET （Brunauer-Emmet-Teller）只是对N2-Sorption isotherm中p/p0=0.05~0.35之间的一小段用传说中的BET公式处理了一下，得到单层吸附量数据Vm，然后据此算出比表面积，如此而已。

◆六类吸附等温线类型几乎每本类似参考书都会提到，前五种是BDDT(Brunauer-Deming-Deming-T eller)分类，先由此四人将大量等温线归为五类，阶梯状的第六类为Sing增加。

每一种类型都会有一套说法，其实可以这么理解，以相对压力为X轴，氮气吸附量为Y轴，再将X轴相对压力粗略地分为低压（0.0-0.1）、中压(0.3-0.8)、高压（0.90-1.0）三段。

那么吸附曲线在：低压端偏Y轴则说明材料与氮有较强作用力(?型，??型，Ⅳ型)，较多微孔存在时由于微孔内强吸附势，吸附曲线起始时呈?型；低压端偏X轴说明与材料作用力弱(型，Ⅴ型)。

中压端多为氮气在材料孔道内的冷凝积聚，介孔分析就来源于这段数据，包括样品粒子堆积产生的孔，有序或梯度的介孔范围内孔道。

BJH方法就是基于这一段得出的孔径数据；高压段可粗略地看出粒子堆积程度，如?型中如最后上扬，则粒子未必均匀。

平常得到的总孔容通常是取相对压力为0.99左右时氮气吸附量的冷凝值。

◆几个常数※液氮温度77K时液氮六方密堆积氮分子横截面积0.162平方纳米，形成单分子层铺展时认为单分子层厚度为0.354nm※标况（STP）下1mL氮气凝聚后（假定凝聚密度不变）体积为0.001547mL例：如下面吸脱附图中吸附曲线p/p0最大时氮气吸附量约为400 mL，则可知总孔容＝400*0.001547＝400/654＝约0.61mL ※STP每mL氮气分子铺成单分子层占用面积4.354平方米例：BET方法得到的比表面积则是S/(平方米每克)＝4.354*Vm，其中Vm由BET方法处理可知Vm=1/(斜率＋截距)◆以SBA-15分子筛的吸附等温线为例加以说明此等温线属IUPAC 分类中的IV型，H1滞后环。

N2吸脱附曲线说明

N2吸脱附曲线说明计算氮等温吸附和解吸的比表面积和孔径分布的几点注意事项我们获得的数据只是真实的吸收-解吸曲线。

比表面积、孔径分布、孔容等都是主观和人为的数据。

经常听到一些学生说要做一个BET，但他们实际做的不是BET，而是氮气等温吸附-解吸曲线。

BET(Brunauer-Emmet-Teller)只处理N2-N2-吸附等温线中p/p0=0.05~0.35之间的一小段，用著名的BET公式获得单层吸附数据Vm，然后根据它计算比表面积，如此而已。

◆六种吸附等温线几乎每一本类似的参考书都会提到前五类是BDDT(布鲁纳-戴明-戴明-泰勒)。

首先，他们四个人把大量的等温线分成五类，而第六类台阶状的是星升。

每种类型都有一组语句。

事实上，可以理解，相对压力是X轴，氮吸附量是Y轴。

X轴相对压力大致分为三个部分:低压(0.0-0.1)、中压(0.3-0.8)和高压(0.90-1.0)。

那么吸附曲线为:低压端偏离y轴表明材料对氮气有很强的作用力。

类型？？类型，类型iv)，许多微孔由于微孔隙中的强吸附势，显示在吸附曲线的起点？类型；材料作用力(？)对低压端偏离x轴的解释较弱？？类型五)。

中压端主要是氮气在材料孔隙中的冷凝和积聚。

中孔分析来自这些数据，包括样品颗粒堆积产生的孔和有序或梯度中孔内的孔。

BJH方法基于本节获得的孔径数据。

高压段可以大致看出颗粒堆积的程度，如？如果模型最终上升，粒子可能不均匀。

通常，当相对压力约为0.99时，获得的总孔体积通常是氮吸附的冷凝值。

◆几个常数※液氮温度为77K时，液氮六方密堆积态氮分子的横截面积为0.162平方纳米，形成单层铺展时，单层厚度为0.354纳米※在标准温度和压力下冷凝1毫升氮气后(假设冷凝密度不变)，体积为0.001547毫升例如，当吸附曲线p/p0在下面的吸附图中最大时，如果氮气的吸附容量为约400毫升，可以看出总孔体积= 400 * 0.001547 = 400/654 =约0.61毫升STP占地4.354平方米/毫升的氮分子铺砌成单层。

吸附容量的曲线n

Available online at Colloids and Surfaces A:Physicochem.Eng.Aspects320(2008)11–18Kinetics of adsorption of Saccharomyces cerevisiae mandelated dehydrogenase on magnetic Fe3O4–chitosan nanoparticlesGui-Yin Li a,b,Yu-Ren Jiang a,∗,Ke-Long Huang a,∗,Ping Ding a,Li-Li Yao aa College of Chemistry and Chemical Engineering,Central South University,Hunan410083,Chinab Hunan Vocational College of Science and Technology,Changsha,Hunan410118,ChinaReceived4August2007;received in revised form17December2007;accepted1January2008Available online19January2008AbstractThe adsorption of Saccharomyces cerevisiae mandelated dehydrogenase(SCMD)protein on the surface-modiﬁed magnetic nanoparticles coated with chitosan was studied in a batch adsorption system.Functionalization of surface-modiﬁed magnetic particles was performed by the covalent binding of chitosan onto the surface of magnetic Fe3O4nanoparticles.Characterization of these particles was carried out using FTIR spectra, transmission electron micrography(TEM),X-ray diffraction(XRD)and vibrating sample magnetometry(VSM).Magnetic measurement revealed that the magnetic Fe3O4–chitosan nanoparticles were superparamagnetic and the saturation magnetization was about37.3emu g−1.The adsorption capacities and rates of SCMD protein onto the magnetic Fe3O4–chitosan nanoparticles were evaluated.The adsorption capacity was inﬂuenced by pH,and it reached a maximum value around pH8.0.The adsorption capacity increased with the increase in temperature.The adsorption isothermal data could be well interpreted by the Freundlich isotherm model.The kinetic experimental data properly correlated with theﬁrst-order kinetic model,which indicated that the reaction is the adsorption control step.The apparent adsorption activation energy was27.62kJ mol−1and the ﬁrst-order constant for SCMD protein was0.01254min−1at293K.©2008Published by Elsevier B.V.Keywords:Adsorption kinetics;SCMD;Magnetic Fe3O4–chitosan nanoparticles1.1ntroductionAdsorption is a conventional but important separation pro-cess.It has been used widely in the chemical,analytical, environmental and biologicalﬁelds,especially in the separation of proteins.In most cases,the adsorbents have diameters in the range of submicron to micron and have large internal porosities to ensure adequate surface area for adsorption[1].However, the diffusion limitation within the particles leads to decreases in the adsorption rate and available capacity.Therefore,it is important and interesting to develop a novel adsorbent with a large surface area for adsorption,a small diffusion resistance and a high capacity for large solutes.Nanotechnology has been quickly developed in variousﬁelds in the past pared to the traditional micron-sized supports used in separation pro-∗Corresponding authors.Tel.:+867318836834;fax:+867318859988.E-mail addresses:jiangyr@(Y.-R.Jiang),klhuang@(K.-L.Huang).cess,nano-sized carriers possess quite good performance due to high speciﬁc surface area and the absence of internal diffusion resistance[2].Magnetic particles ranging from nanometer to micrometer scale are being used in an increasing number of bioapplica-tions[3]such as the immobilization of proteins,peptides and enzymes[4,5],bioafﬁnity adsorbents[6],drug delivery[7,8], biosensor[9]and so on.Particles in the nanosize range possess distinctively different physiochemical,magnetic,and optical properties compared to their bulk phase.The ideal magnetic nanoparticles for bioapplications would have these desirable properties,i.e.,uniform size,high surface area,fast adsorption kinetics,biocompatibility,as well as superparamagnetism with high magnetic strength[10,12].Thus,there are many reports on using nanosize magnetic bodies to adsorb proteins[11,12], enzymes which include lipase,ribonuclease,lysozyme,peni-cillin G acylase,glucose oxidase and so on[13–16].Often,an additional inorganic or polymeric coating layer is necessary to avoid magnetically induced self-aggregation of magnetic cores and to improve the functionality or biocompatibility of these0927-7757/$–see front matter©2008Published by Elsevier B.V. doi:10.1016/j.colsurfa.2008.01.01712G.-Y.Li et al./Colloids and Surfaces A:Physicochem.Eng.Aspects320(2008)11–18nanostructures.Shamim et al.[17,18]prepared an organic–inorganic nanoadsorbent with a mean diameter of12nm using surface modiﬁed Fe3O4as the core and N-isopropylacrylamide as the polymer shell.These thermosensitive nanoparticles were used as a bioseparation tool for the separation of BSA.The adsorption and desorption was done quickly due to high adsorp-tion capacity.Bucak et al.[19]synthesized phospholipid-coated colloidal magnetic nanoparticles with mean magnetite core size of8nm for the adsorptive separation of model hydrophilic pro-teins.These particles were of high adsorptive capacities(up to1200mg protein/ml adsorbent),and used as effective ion exchange media for the recovery and separation of proteins from protein mixtures and exhibited none of the diffusion resistances offered by conventional porous ion exchange media.Alcohol dehydrogenase which catalyzes the oxidation of alcohols and the reduction of carbonyl compounds such as alde-hydes and ketones has attracted attention because of its potential applications in the production of various starting materials and intermediates in chemical industry.It is well known that Saccha-romyces cerevisiae possesses several alcohol dehydrogenases and shows good capacity as a redox biocatalyst in a variety of stereoselective reductions and in the regeneration of coenzymes NAD(P)H in vivo continuously[20].S.cerevisiae mandelated dehydrogenase(SCMD),a kind of alcohol dehydrogenases,can catalyze the reduction of phenylglyoxylic acid to(R)-mandelic acid[21],which is widely used as a precursor for the manufac-ture of semi-synthetic penicillin and cephalosporin and also for the synthesis of various other pharmaceuticals[22].The characteristic of protein adsorption on surfaces of mag-netic particles is of particular importance as it reﬂects the interaction between synthetic materials and the biomolecule of interest.Besides mimicking some of the in vivo processes like drug delivery,the adsorption of protein is also a key reaction step in many bioprocesses found in the food and pharmaceutical industries[11].The goal of this paper is to report on the syn-thesis of single-domain magnetic nanoparticles with chitosan coatings and on their use in the adsorptive immobilization of the SCMD.The equilibrium of adsorption SCMD onto the magnetic Fe3O4–chitosan nanoparticles was investigated in detail and the kinetic of adsorption was also suggested.2.Materials and methods2.1.MaterialsStrains(S.cerevisiae,strain No.3)used in this work were obtained from our culture collection and alcohol dehydroge-nase(EC1.1.1.1)from S.cerevisiae was prepared as described in Section 2.5.Phenylglyoxylic acid was purchased from Sigma Chemical Company.Nicotinamide adenine dinucleotide, reduced form(NADH)was procured from Roche Ltd.Chitosan (CTS,MW4.9×105,degree of deacetylation95%)was pro-cured from Dalian Xindie Chitin Company(Dalian,China). 25%Glutaraldehyde solution was purchased from Hunan Nor-mal University Chemical Company(Hunan,China).Ferrous sulphates heptahydrate and aqueous ammonia solution were purchased from Tianjin No.3Chemical Plant(Tianjin,China).Other chemicals were the analytic grade reagents commercially available and used without further puriﬁcation.All solutions were prepared with distilled,and deionized water.2.2.Synthesis of Fe3O4magnetic nanoparticles by hydrothermal methodFe3O4nanoparticles were prepared by hydrothermal method with a ferrous complex using H2O2as an oxidizer.Ferrous sul-phates heptahydrate(2.50g)were dissolved in30ml water,then 10ml50g L−1PEG-20000and30ml NH4OH solution were added to the solution at30◦C under vigorous stirring.During the reaction process,the pH was maintained at about10.After-wards,0.27ml of30%H2O2solution was added to the stirred mixture for20min.The mixture was put into the autoclaves and heated at160◦C for5h in a furnace.The Fe3O4nanopar-ticles were gained by centrifugation at8025×g for15min and washed several times with water and ethanol,andﬁnally dried in a vacuum oven at70◦C.2.3.Preparation of magnetic Fe3O4nanoparticles coated with chitosanFe3O4nanoparticles(0.2g)were washed with99.5%ethanol twice and dispersed in a solution with30ml parafﬁn and0.5ml span-80,then15.0ml of chitosan(0.2g)dissolved in acetic acid with concentration of5%were added.The suspension was mixed by ultrasonic irradiation for30min.The suspension was then transferred into a three-neckedﬂask with a mechanical stir-rer after adding3ml25%glutaraldehyde solution.After4h,the Fe3O4–chitosan nanocomposite particles were recovered from the reaction mixture by placing the bottle on a permanent magnet with a surface magnetization of6000G.The magnetic particles settled within1–2min.The supernatant was removed and the precipitant were washed several times with water and ethanol and dried at50◦C in a vacuum oven.2.4.Particles characterizationThe average particle size and morphology of the samples were observed by TEM using a H-600transmission electron microscope.XRD measurement was performed on a Philips D/Max-2500diffractometer,using a monochromatized X-ray beam with nickel-ﬁltered Cu K␣radiation with4◦min−1scan rate.A continuous scan mode was used to collect2θdata from 10◦to90◦.The magnetization curves of the dried microspheres were recorded with a JDM-13D magnetometer.The hysteresis of the magnetization was obtained by changing H between+4000 and−4000Oe at25◦C.FTIR spectra of CTS,Fe3O4nanoparti-cles and Fe3O4–chitosan nanoparticles were recorded with KBr discs in the range of4000–400cm−1on Nicolet A V ATAR360 Fourier-transfer infrared.2.5.Production and puriﬁcation of SCMDS.cerevisiae was cultivated in Rough bottles in the follow-ing culture medium(g/L):glucose50,peptone3.0,yeast extractG.-Y.Li et al./Colloids and Surfaces A:Physicochem.Eng.Aspects320(2008)11–18132.5,K2HPO41.0,MgSO4·7H2O0.5,NaCl0.5,Fe2(SO4)30.01,ZnSO40.01,pH6.5.The cells were incubated at30◦C and har-vested after24h.Then the cells were collected from culture bycentrifugation at6687.5×g at4◦C for15min.Cell pellets weresuspended with10ml0.9%sterile physiological saline per gramof cell pellet and disrupted by using Ultrasonic vibra cell crusherKS-250F(power400W,120times,work8s,stop8s).The dis-rupted cell mixture was centrifuged at6687.5×g for10minat4◦C and the supernatant was collected and precipitated withammonium sulphate atﬁnal concentration of3M.The precipi-tant was collected by centrifugation at6687.5×g for15min at4◦C and then resuspended in5ml of phosphate buffer(0.2M,pH6.8)per100mg of precipitant.The resuspended solution wasdialyzed overnight against500ml of phosphate buffer(0.2M,pH6.2).The dialyzed sample was clariﬁed by centrifugation at12,000×g for20min and the crude SCMD protein solution wasobtained in the supernatant.2.6.Protein adsorption on magnetic Fe3O4–chitosannanoparticlesMagnetic Fe3O4–chitosan nanoparticles(50mg)were redis-persed in30ml of5%glutaraldehyde phosphate buffer solutionat pH6.8and kept at room temperature for10h.The nanoparti-cles were separated by magnetic decantation placing the bottleon a permanent magnet with a surface magnetization of6000G,and washed several times with deionized water.Then differ-ent concentrations of SCMD solution(30ml0.2mM phosphatebinding buffer,pH8.0)were added to the particles.The resultingsuspensions were subsequently incubated at room temperaturewith shaking for3h,which proved to be a sufﬁcient period toreach equilibrium.At the end of incubation,the immobilizedSCMD were separated by magnetic decantation,washed with aphosphate buffer solution at pH7.0(5×2ml),and were used tomeasure the activity of the immobilized SCMD.The supernatantSCMD concentration was determined by Lab Tech UV2100spectrophotometer(absorption at280nm)with bovine serumalbumin as the standard.The protein adsorption capacity wascalculated by mass balance.The adsorbed amount of SCMD perunit weight of magnetic Fe3O4–chitosan nanoparticles at time t,Q(t)(mg g−l)was calculated from the mass balance equation asQ(t)=(C0−C t)Vm(1)where C0and C t(mg ml−1)are the initial SCMD concentration and the SCMD concentrations at any time t,respectively;V is the volume of the SCMD solution;and m is the weight of the magnetic Fe3O4–chitosan nanoparticles.2.7.Activity measurementThe activity of SCMD immobilization onto the magnetic Fe3O4–chitosan nanoparticles was determined according the references[23,24]with some modiﬁcations.The activity of immobilized SCMD was determined by measuring the initial reduction rate of phenylglyoxylic acid by SCMD at the desired temperature following the decrease in absorbance of NADH at 340nm on a Lab Tech UV2100spectrophotometer.Generally, 4ml phosphate buffer solution(0.02M,pH7.0),1ml1mM NADH solution and1ml0.1M phenylglyoxylic acid solution were mixed to the test tube,then10mg SCMD-immobilized magnetic nanoparticles(1ml0.14mg/ml SCMD solution immo-bilized on the10mg magnetic nanoparticles)was added.After mixing for several minutes by vortex,the liquid solution sepa-rated from the magnetic nanoparticles via a permanent magnet was used for the analysis of NADH concentration.To compare the activity of SCMD with and without immo-bilized the magnetic Fe3O4–chitosan nanoparticles,the initial reduction rate of phenylglyoxylic acid by free SCMD follow-ing the decrease of NADH concentration was measured at the same condition as that of SCMD immobilized on the magnetic Fe3O4–chitosan nanoparticles.One unit of SCMD activity(U)was deﬁned as the amount of SCMD which used up1nm NADH per minute at25◦C and pH 7.0.3.Results and discussion3.1.Characterization of the magnetic nanoparticlesFig.1showed the FTIR spectra of the naked Fe3O4(a), CTS(b)and Fe3O4–chitosan nanoparticles(c).The peak around 3440cm−1observed in curve b and c relates to the–OH group. For the naked Fe3O4(Fig.1(a)),the peak at569cm−1relates to Fe–O group.For the IR spectrum of CTS(Fig.1(b)),the charac-teristic absorption bands appeared at1589cm−1which can be assigned to N–H bending vibration,peaks1399cm−1appeared to–C–O stretching of primary alcoholic group in chitosan.In the spectrum of Fe3O4–chitosan nanoparticles(Fig.1(c)),compared with the spectrum of CTS,the1589cm−1peak of N–H bending vibration shifted to1562cm−1,and a new sharp peak1627cm−1 appeared,it indicated that chitosan react with glutaraldehyde to form Schiff base,and a new sharp peak560cm−1relates toFe–O Fig.1.FTIR spectra of the naked Fe3O4(a),CTS(b)and Fe3O4–chitosan nanoparticles(c).14G.-Y.Li et al./Colloids and Surfaces A:Physicochem.Eng.Aspects 320(2008)11–18Fig.2.TEM micrographs for magnetic nanoparticles without (a)and with (b)chitosan,the bar is 100nm.group appeared.The results indicated that CTS was coated to the magnetic Fe 3O 4nanoparticles successfully.Because the sur-face of iron oxide with negative charges has an afﬁnity toward CTS,protonated CTS could coat the magnetite nanoparticles by the electrostatic interaction and chemical reaction through glutaraldehyde cross-linking.The typical TEM micrographs for magnetic nanoparticles with and without chitosan coating were shown in Fig.2.From Fig.2(a),it was clear that the naked Fe 3O 4nanoparticles were essentially monodisperse and had a mean diameter of 20nm.After coating with chitosan (Fig.2(b))the particles remained dis-crete with a mean diameter of about 25nm.This revealed that the coating process did not signiﬁcantly result in the agglomeration and the change in size of the particles.This could be attributed to the reaction occurring only on the particle surface.But there is little aggregative phenomenon in the Fe 3O 4nanoparticles coated with chitosan.Fig.3showed the XRD patterns for the naked and Fe 3O 4nanoparticles coated with chitosan.It indicated that Fe 3O 4isFig.3.XRD patterns for magnetic nanoparticles without (a)and with (b)chi-tosan.the dominant phase in both the samples,but the entire peak is broadened.Six characteristic peaks for Fe 3O 4marked by their indices ((220),(311),(400),(422),(511)and (440))were observed for both samples.These peaks are consistent with the database in JCPDS ﬁle (PDF No.65-3107)and reveal that the resultant nanoparticles were pure Fe 3O 4with a spinel structure.It is also explained that the coating process did not result in the phase change of Fe 3O 4.Fig.4showed the magnetization curves of (a)magnetic Fe 3O 4particles (b)magnetic Fe 3O 4–chitosan nanoparticles obtained by VSM at 25◦C.The saturation magnetization (σs )of the chitosan-magnetite nanocomposites was about 37.3emu g −1,while for the pure magnetite nanoparticles the σs was 83.2emu g −1.As could be seen in Fig.4,no remainance and coercivity is observed,which indicated that the magnetic nanoparticles are superparamagnetic.Superparamagnetism (i.e.responsiveness to an applied magnetic ﬁeld withoutretainingFig.4.Magnetization curves of (a)magnetic Fe 3O 4particles and (b)magnetic Fe 3O 4–chitosan nanoparticles obtained by VSM at 25◦C.G.-Y.Li et al./Colloids and Surfaces A:Physicochem.Eng.Aspects320(2008)11–1815Fig.5.Adsorption kinetic of SCMD protein on the magnetic Fe3O4–chitosan nanoparticles with different pH(temperature25◦C).any magnetism after removal of the magneticﬁeld.)is an espe-cially important property needed for magnetic targeting carriers. These results also indicated that the single domain magnetic nanoparticles remained in these polymer nanoparticles.The decrease of the saturation magnetization is most likely attributed to the existence of span-80on the surface of Fe3O4nanoparti-cles which may create a magnetically dead layer.In addition,the magnetic molecules on the surface lack complete coordination and thus increase the surface spin disorientation.This disordered structure in the amorphous materials and at the interface might have caused a decrease in the effective magnetic moment[17].3.2.Effect of pH on SCMD protein adsorptionFig.5showed the effect of pH on the adsorption of SCMD onto the magnetic Fe3O4–chitosan nanoparticles.The adsorp-tion capacity increases with increasing pH of the solution(pH 5.8–8.0).The maximum adsorption capacity of SCMD on mag-netic Fe3O4–chitosan nanoparticles is found at pH8.0.This could be explained by the fact that at low pH,more protons will be available to protonate amine groups to form groups NH3+,reducing the number of binding sites for the adsorption of SCMD.The adsorption behavior showed that adsorption of protein onto magnetic nanoparticles is governed by hydropho-bic interaction and by electrostatic interactions[18,25].The inﬂuence of pH on the adsorption capacity showed decreasing afﬁnity with increasing electrostatic repulsion between protein and adsorbent and a maximum plateau value at pH8.0.3.3.Adsorption isotherm of SCMD proteinFig.6displayed the equilibrium adsorption data con-cerning the adsorption of SCMD protein on the magnetic Fe3O4–chitosan nanoparticles at4,20,30and45◦C,respec-tively.There was a gradual increase of adsorption for SCMD protein until equilibrium was attained.The adsorption capacities at different temperatures are very different.Adsorption isotherm is important to describe how solutes interact with adsorbent.The Fig.6.Adsorption isotherms of SCMD protein on the magnetic Fe3O4–chitosan nanoparticles at4,20,30and45◦C,respectively.Langmuir and Freundlich models are frequently employed to describe the adsorption process.The Langmuir adsorption model is given asQ=K L Q m C1+K L C(2)where Q is the amount of SCMD protein adsorbed per unit weight of the magnetic Fe3O4–chitosan nanoparticles at equilib-rium concentration(mg g−1),C is the equilibrium concentration in the solution(mg ml−1),Q m is the maximum adsorption at monolayer coverage(mg g−1),and K L is the Langmuir constant related to the afﬁnity of binding sites(ml mg−1).Eq.(2)can also be expressed as follows:CQ=CQ m+1Q m K L(3) Freundlich adsorption isotherm model,which is an empirical equation used to describe heterogeneous adsorption systems, can be represented as follows:Q=K F C1/n(4)where Q and C are deﬁned as above,K F is Freundlich con-stant representing the adsorption capacity(mg g−1),and n is the heterogeneity factor depicting the adsorption intensity.In most reference,Freundlich adsorption Eq.(4)may also expressed as Eq.(5)log Q=log K F+1n log C(5) Weﬁt the adsorption isotherms in Fig.6to Langmuir and Freundlich adsorption equations.The regression equations, parameters K L,K F and n,as well as the correlation coefﬁ-cients R are summarized in Table1.It is shown that Freundlich isotherm is suitable for characterizing the experimental adsorp-tion isotherms since all of the correlation coefﬁcients are larger than0.99.As known to us all,Langmuir isotherm is on the supposition that the surface of the adsorbent is a homogeneous16G.-Y.Li et al./Colloids and Surfaces A:Physicochem.Eng.Aspects 320(2008)11–18Table 1The regression results for adsorption of SCMD protein on the magnetic Fe 3O 4–chitosan nanoparticles Temperature (◦C)The regression equation K L Q m R Langmuir isotherm equation 4C /Q =0.00855+0.00715C 139.8600.8360.94920C /Q =0.00416+0.00846C 118.203 2.0340.98930C /Q =0.00417+0.00713C 140.252 1.7090.99145C /Q =0.00398+0.00655C 152.671 1.6540.988Temperature (◦C)The regression equation K F n R Freundlich isotherm equation 4log Q =1.82972+0.75842log C 67.656 1.3190.99720log Q =1.94116+0.60433log C 87.329 1.6550.99630log Q =1.99194+0.64765log C 98.161 1.5440.99845log Q =2.02201+0.65600log C105.1971.5240.998surface,whereas Freundlich isotherm is applied to the adsorp-tion process on a heterogeneous ngmuir adsorption model is classically used for protein adsorption at an interface,surface,or membranes [26,27].The Langmuir model assumes that the adsorption can take place only at speciﬁc localized sites on the surface and that the saturation coverage corresponds to complete occupancy of these sites.At 20,and 30◦C,the experi-mental adsorption isotherm data can ﬁt the Langmuir adsorption model well.3.4.Kinetics of adsorptionThe adsorption kinetic experiments were carried out to eval-uate the rate and the activation energy of the SCMD protein adsorption process on the magnetic Fe 3O 4–chitosan nanoparti-cles.The kinetics of the adsorption process was followed by determining the amounts of adsorbed SCMD protein at var-ious time intervals in the following temperatures:4,20,30and 45◦C,as shown in Fig.7.The results indicated thattheFig.7.Adsorption kinetic of SCMD on the magnetic Fe 3O 4–chitosan nanopar-ticles with different temperature (initial protein concentrations:0.14mg/ml,pH 8.0).amount of SCMD adsorbed was not affected signiﬁcantly over the examined temperature range.The time necessary to reach equilibrium for the different studied temperatures is practically about 180min and signiﬁcant increases in the adsorbed amounts are not observed after the equilibrium stage.It is also a well-recognized fact that the process of adsorp-tion is a two-regime process [28].At the initial stage,the solid surface is bare,and the kinetics of adsorption is governed by the diffusion of the molecules from the bulk solution to the surface.All of the molecules that arrive at the surfaces are assumed to be immediately adsorbed.The mass transport can be interpreted as a Fickian diffusion equation:Q t =k i t 0.5(6)where k i is the diffusion rate (mg g −1min −0.5).The experimen-tal data (shown in Fig.7)were plotted as Q t versus t 0.5and the results were shown in Fig.8.From the slope of the curve Q t as a function of t 0.5,the diffusion constant k i can becalculated.Fig.8.Plot of the Fickian diffusion equation at different temperatures.G.-Y.Li et al./Colloids and Surfaces A:Physicochem.Eng.Aspects 320(2008)11–1817Table 2Adsorption kinetic parameters at different temperature Fickian diffusion model Pseudo ﬁrst-order model Temperature (◦C)k i (mg g −1min −0.5)R k 1(min −1)Q e ,cal R4 1.06540.98150.0141614.69740.9948200.81390.99310.0125410.39740.9976300.83510.94490.0208412.52030.9927450.49320.90530.030169.65950.9878In the later stage,a barrier of adsorbed molecules exists,and the molecules arriving from solution have to diffuse across this barrier.This penetration is slow,and the speciﬁc rate constants of the SCMD protein adsorption can be determined from the pseudo ﬁrst-order kinetic model—Lagergren Equation ln(Q e −Q t )=ln Q e −k 1t(7)where Q e and Q t are the amounts of SCMD protein adsorbed on adsorbent (mg g −1)at equilibrium and at time t ,respectively,and k 1is the rate constant of ﬁrst-order adsorption (min −1).Straight-line plots of log(Q e −Q t )against t were used to determine the rate constant,k 1and correlation coefﬁcient.With the help of Figs.8and 9,drawn in accordance with Eqs.(6)and (7),respectively,the diffusion constant k i and the ﬁrst-order rate constants k 1have been calculated.These were summarized in Table 2.Based on the correlation coefﬁcients,the adsorptions of SCMD protein were best described by the ﬁrst-order equation,similarly to other report of the protein adsorption on solid phases [28,29].The ﬁrst-order kinetic process has been used for reversible reaction with an equilibrium being estab-lished between liquid and solid phases.Generally,a rise in temperature of a chemical reaction increases the rate of the reaction,and the temperature depen-dence results in a change in the rate constant.Activation energy of the sorption can be estimated by Arrhenius equation provid-ing the relationship between the rate constant andtemperatureFig.9.Plot of the pseudo ﬁrst-order equation at different temperatures.as shown in the following equation:ln k =ln A −E a RT(8)where k is the rate constant of adsorption,A the Arrhenius con-stant which is a temperature independent factor,E a the activation energy,R the gas Constant and T is the solution temperature in Kelvin.In this work,activation energy of sorption process has been calculated using the values of rate constant from a ﬁrst-order kinetic equation and using the appropriate solution temperatures.The plots of ln k versus 1/T were found to be lin-ear in the temperatures range of 20–45◦C.The value of E a from the slope of the plot was 27.62kJ mol −1.The relatively low acti-vation energy indicates the adsorption of SCMD is easily taken place by the magnetic Fe 3O 4–chitosan nanoparticles.3.5.Activity of immobilized SCMDThe effect of adsorption on the activity of SCMD was exam-ined to demonstrate the practicability for biocatalysing the reduction of phenylglyoxylic acid to (R )-mandelic acid.Fol-lowing the determination activity of SCMD with and without immobilized Fe 3O 4–chitosan method,we measured the activity of free SCMD and immobilized SCMD at 25◦C and pH 7.0.For free SCAD,the activity is 360.655U,while for the immobilized SCMD,the activity is 176.014U,48.8%activity was retained.The duration of a catalyst is an important feature for its potential application in industry.To investigate the reusability of immobilized SCAD,several repetitive use of immobilized SCAD were operated.After each cycle,the immobilized SCAD was recovered by magnetic separation and recycled for the reduction of phenylglyoxylic acid.The activity of the ﬁrst batch was taken as 100%.The assay condition remained the same for all batches.Within seven cycles of usage,the remaining activity was about 100%,89.15%,79.42%,69.50%,62.80%,56.48%,and 48.26%of the ﬁrst use.The activity of the immobilized SCAD in the repeated use did not decrease signiﬁcantly.Although the immobilized SCMD activity decreased signiﬁ-cantly,the immobilized SCMD had a good durability and could be readily recovered by magnetic separation.This revealed the magnetic Fe 3O 4–chitosan nanoparticles indeed could be practi-cally used for the immobilized of enzymes.4.ConclusionsMagnetic Fe 3O 4–chitosan nanoparticles were fabricated by the covalent binding of chitosan onto the surface of the mag-。

常见吸附等温曲线的类型及其理论分析PPT课件

2.BET方程建立的几个假设： • 与Langmuir方程相同的假设
•第一层的吸附热是常数，第二层以后各层的吸附热都相等并等同于凝聚热 •吸附是无限层
3. 方程的推导
θ0
θ1
θ2
θ3

1 i i0

n nm ii
(6)
i0
气体分子在第零层上吸附形成第一层的速度等于第一层脱附形成第零层的速度：
3.Kelvin方程对Ⅳ和Ⅴ型等温线的解释：
n
B A 0
D C
临界温度以下，气体在中孔吸附剂上发生吸附时，首先形成单分子吸附层，对应图中的AB段，当单分子层吸附接近饱和时（达到B 点），开始发生多分子层的吸附，从A点到C点，由于只发生了多
D' E
分子层吸附，都可以用BET方程描述。当相对压力达到与发生毛细凝聚的Kelvin半径所对应的某一特定值，开始发生毛细孔凝聚。如果吸附剂的空分布比较窄（中孔的大小比较均一），CD段就会比较陡，如果空分布比较宽，吸附量随相对压力的变化就比较缓慢如 p/p0 CD‘段。当孔全部被填满时，吸附达到饱和，为DE段。对于Ⅳ和Ⅴ 型等温线的区别，可以参考Ⅱ和Ⅲ型等温线。当吸附剂与吸附质之间的作用比较弱时，就会出现Ⅴ型等温线。
B n
0
p/p0 开始凝聚
开始蒸发
B类回线：典型的例子是具有平行板结构
的狭缝孔。开始凝聚时，由于气液界面
是大平面，只有当压力接近饱和蒸汽压
时才发生毛细凝聚（吸附等温线类似Ⅱ
型）。蒸发时，气液界面是圆柱状，只
有当相对压力满足蒸发才能开始。
ln
p p0
d

VL RT
1 rk
n
B 0

径向流分子筛吸附器流场数值模拟

收稿日期:2009212230作者简介:李剑锋,男,1983年生,2009年毕业于江苏工业学院化工过程机械专业,现在杭州杭氧股份有限公司设计研究院从事分子筛吸附器等单元设备的开发、设计工作。

径向流分子筛吸附器流场数值模拟李剑锋1,周寒秋2,林秀娜3(1、31杭州杭氧股份有限公司设计研究院,浙江省杭州市东新路388号　310004;21杭州杭氧股份有限公司石化工程公司,浙江省杭州市东新路388号　310004) 摘要:介绍了径向流分子筛吸附器的主要结构和工作原理。

采用CFD 软件对径向流分子筛吸附器流场进行了模拟计算,分析了径向流分子筛吸附器流场压力分布和气体流动速度分布,比较分子筛层和氧化铝层中不同位置处的速度分布曲线,预测径向流分子筛吸附器吸附工作时吸附饱和临界突破位置。

关键词:空分设备;分子筛吸附器;径向流;流场;数值模拟中图分类号:TB662 文献标识码:AFlow f ield numerical simulation of radial flow molecular sieve adsorberLi Jianfeng 1,Zhou Hanqiu 2,Lin Xiuna 3(1、31Designi ng Instit ute ,Hangz hou Hangyang Co.,L t d.,388Dongxi n Road ,Hangz hou 310004,Zhejiang,P.R.Chi na ;21Pet ro 2chem icalEngi neeri ngCom pany ,Hangz houHangyang Co.,L t d.,Dongxi n Road ,Hangz hou 310004,Zhejiang ,P.R.Chi na )Abstract :Here ,the main structure and working principle of radial flow molecular sieve adsorber are briefed.The simulation calculation is made with CFD software for the flow field of radial flow molecular sieve adsorber ,the pressure distribution and gas flow velocity distribution of the said field are analyzed ,the velocity distribution curves at different positions between molecular sieve layer and alumina layer are compared ,and the critical saturated adsorption breaking through position of the said adsorber during adsorption is predicted.K eyw ords :Air separation plant ;Molecular sieve adsorber ;Radial flow ;Flow field ;Numerical simulation 分子筛吸附器在空气分离系统中起到吸附原料空气中的水分、二氧化碳和碳氢化合物等杂质的作用。

吸附常用公式

吸附常用公式：一.Freundlich 等温式：n /1kc q =或c lg n1k lg q lg +=，q 平衡吸附量mg/g ；c 平衡浓度mg/L 一般认为：1/n 的数值一般在0与1之间，其值的大小则表示浓度对吸附量影响的强弱。

1/n 越小，吸附性能越好。

1/n 在0.1~0.5，则易于吸附；1/n>2时难以吸附。

k 值可视为c 为单位浓度时的吸附量，一般说来，k 随温度的升高而降低Ki/n 吸附容量吸附强度。

二.Langmuir 等温式：bc1bc q q e +=或（1）e e q 1c 1b q 1q 1+⋅=或（2）b q 1c q 1q c e e += q 平衡吸附量mg/g ；c 平衡浓度mg/L ；q e 饱和吸附量mg/g一般c 值<1时采用（1）式；c 值较大时采用（2）式。

符合Langmuir 等温式的吸附为化学吸附。

化学吸附的吸附活化能一般在40~400kJ/mol 的范围，除特殊情况外，一个自发的化学吸附过程，应该是放热过程，饱和吸附量将随温度的升高而降低。

b 为吸附作用的平衡常数，也称为吸附系数，其值大小与吸附剂、吸附质的本性及温度的高低有关，b 值越大，则表示吸附能力越强，而且b 具有浓度倒数的量纲。

三.颗粒内扩散方程：5.0t k q ⋅=q 为t 时刻的吸附量mg/g ；t 为吸附时间(min)；k 为颗粒内扩散速率常数(mg·g -1·min -0.5) 四.准二级吸附动力学方程：t q 1q k 1qt e2e2+⋅=q e 、q 分别为吸附平衡及t 时刻的吸附量(mg·g -1)；t 为吸附时间(min)；k 2为准二级吸附速率常数(g·mg -1·min -1)五.二级动力学方程：t k q 1q q 1'2ee +=- q e 、q 分别为吸附平衡及t 时刻的吸附量(mg·g -1)；t 为吸附时间(min)；k 2‘为二级吸附速率常数(g·mg -1·min -1)六.Lagergren 方程（准一级吸附动力学方程）：ln(q e －q)=lnq e －k 1tq e 、q 分别为吸附平衡及t 时刻的吸附量(mg·g -1)；t 为吸附时间(min)；k 1为准一级吸附速率常数(min -1)七.二级反应模型：tc k 11c c 0'20⋅⋅+= c 0、c 分别为溶液中初始及t 时刻溶液的浓度(mg·L -1)；t 为吸附时间(min)；k 2‘为二级反应速率常数(L·mg -1·mi n -1)当吸附过程为液膜扩散控制时，t 与ln(q e －q)成直线关系，并通过坐标原点；Mckay 等人认为,当t 0.5应与q 成直线关系且通过原点时，则说明物质在颗粒内扩散过程为吸附速率的唯一控制步骤。

径向流氦氢分离床穿透特性实验与模拟分析

散系数$表达式!!+"如下#=89%c%!%!,!c S-!J#;!J槡W!%>'M&#!,+%;'M&W!,"+'%S&式中#,为气体温度+J#*JW为组分#*W的相对摩尔质量+'M#*'M W为组分#*W的分子体积)如果气体密度不大$多孔介质的孔径较小$气体的分子平均自由程可能远大于多孔介质的孔径$此时气体分子与多孔介质孔壁碰撞的机会大于气体分子间的碰撞$阻碍气体扩散的主要因素成为气体分子与多孔介质孔壁的碰撞$此时可考虑Z9C F?39扩散$其表达式如下#=a9*S%%'D,J槡#%(&式中$'j为多孔介质微孔的平均半径$@8)在本实验系统中$经计算$=#W$L远小于=a$说明氢气通过粉末层的扩散机理为分子扩散$==i=#W$L)D C E!初始条件与边界条件初始条件#采用Q N,0型流动模型$床体入口为特定浓度氦氢混合气体$吸附压力为!=:8$设定床体初始压力为%$=$依据床体实际工作温度设定床体初始温度$初始流速为%8,?)边界条件#外部温度边界为恒温$采用速度入口*压力出口边界设定$出口压力边界为!%%a$=$抑制回流$入口速度采用标准质量流量控制)D C F!模型假设在不影响床体吸附过程的前提下$作如下假设)!&忽略气固反应吸附热$设定床体温度均匀)由于径向吸附床结构较小$入口原料气氢浓度为778量级$氦载气流量较大)随着反应的进行$床体温度与床体外侧温度梯度加大$会加快换热效率$达到稳态温度)'&吸附过程中仅考虑氢气的吸附反应$不考虑氦气的表面吸附影响)+&进出口气体为理想气体))&忽略吸附过程对孔隙率的影响)E!结果与分析E C B!模拟分析径向吸附床穿透性能模拟采用参数如表!所列$计算)%%8A9内径向床体的穿透性能)床体粉末层浓度分布云图如图+所示)表B!径向床模拟特性参数:,=-'B!7,!#,-='!6#)/-,+#"*4;,(,4+'(#6+#4&,(,)'+'(6由图+可看出$由于粉末层流场分布均匀$沿粉末层轴向方向浓度云图分布均匀)径向方向存在浓度梯度$且'%%8A9以内$随着时间的推移$传质区在移动$出口浓度一直很低$说明床体保持高效率吸附++%%8A9后$随着吸附反应的推进$吸附效率明显下降$出口浓度与入口浓度差逐渐接近)径向吸附床穿透性能是通过求解稀物质传递方程*动量方程以及吸氢速率的微分方程按照一定的初始条件和边界条件迭代求解的)分析求解图+中不同时刻床体浓度沿吸附层的轴向分布$结果如图)所示)由图)可发现$粉末层在不同时刻所对应的浓度分布曲线基本一致$说明在吸附反应过程中$沿气体径向流动方向$吸附反应以一定的流动速度沿粉末层向出口移动) E C D!特性参数影响分析!&吸附温度表!中其他参数不变$改变粉末层吸附温度%+%+*+'+*+)+*+T+*+(+Z&进行参数化扫描$考察温度对穿透曲线的影响$并与实验结果进行比对$结果如图-所示)由图-可看出$穿透曲线的模拟结果与实验结果线型及变化规律基本一致$在穿透拐点处存在一定偏差$其可能的原因有#理论模型未考虑吸附热效应$粉末自身吸附热效应对传热传质的影响未充分考虑+模型中未考虑粉末层粒度的变化$多次吸放氢循环测试后$材料粒度会减小$吸氢速率有所变化$同时在吸附穿透过程中$由初始的[>Q6相到[>Q6K+相变$相尺寸发生变化$随着吸附的进行$床体径向方向孔隙率呈现一定的变化规律$影响流场分布与物质传递过程$故实际床层内物质状态变化较为复杂$而在模型中未考虑粉末粒度及孔隙率变化的影响)但整体模拟变化规律与实验结果符合较好$说明模型具有一定的有效性))(!原子能科学技术!!第-(卷=111%i !8A 9+R 111%i '%%8A 9+@111%i +%%8A 9+F 111%i )%%8A 9图+!床体浓度分布云图N A E "+!Q 69@39:>=:A 69F A ?:>A R C :A 69@56C F A 8=E36;>=F A =5R 3F 图)!氢气浓度沿粉末层径向分布的动态变化N A E ")!2I 9=8A @4=>A =:A 696;6E39@69@39:>=:A 69F A ?:>A R C :A 69=569E >=F A =56;76X F 3>5=I3>同时由图-可发现$床体温度为+%+#+'+Z 时$床体效率基本一致$之后随着温度的升高$床体效率下降$且下降速率逐渐加大$分析原因如下#[>%c (J A %c 'Q 6材料吸氢的平衡压较低$在+%+#+'+Z 内$随着吸附初期温度的升高$吸氢平衡压增加$吸氢速率压力项变小$结合阿伦尼乌斯公式$温度增加使吸氢速率常数%@&增大$在此阶段$吸氢平衡压增加导致吸氢速率降低的效果与吸氢速率常数增大导致吸氢速率增加的效果基本相同$最终使得吸氢速率变化不大$吸附效率变化不明显+而当温度进一步增大时$吸氢平衡压增加导致吸氢速率降低的效果大于吸氢速率常数增大导致吸氢速率增加的效果$致使整体吸氢速率减小$进而吸附效率下降)图-!床体温度对径向吸附床穿透曲线的影响N A E "-!P 9;5C 39@36;R 3F :3873>=:C >3697393:>=:A 69@C >436;>=F A =5R 3F定义吸附效率**c *b #%c !b 所对应的径向长度为!个传质区长度$为计算方便$穿透点的初始浓度设为%c !b $穿透前吸附床出口处氢浓度需低于%c !b $绘制吸附初期%%i !8A 9&$轴向高度为!-88处床体径向长度方向浓度分布曲线$如图T 所示)由图T 可发现$+%+#+)+Z 温度范围内$随着温度的升高$传质带长度基本不变$为!'c )88+随着温度继续升高$传质带长-(!第!期!!丁卫东等#径向流氦氢分离床穿透特性实验与模拟分析度升高加快$当床体温度升高至+(+Z 时$粉末层厚度不足!个传质区长度$导致初始时刻吸附效率小于!%%b)图T !床体径向长度方向浓度分布随温度的变化N A E "T !Q 69@39:>=:A 69F A ?:>A R C :A 69A 9>=F A =5539E:<F A >3@:A 696;R 3F4=>A 3?X A :<:3873>=:C >3结合模拟结果可知$吸附温度在+%+#+)+Z 之间时$升高温度对传质区长度及出口处浓度,时间曲线影响较小$吸附温度大于+)+Z 后$传质区增大速度加快$吸附效率下降明显)工程应用时$可考虑床体交替工作脱附降温工艺$粉末层无需降至室温$床体温度可控制在室温#+)+Z 之间)图S !氢浓度对径向吸附床穿透曲线的影响N A E "S !P 9;5C 39@36;6E39@69@39:>=:A 69697393:>=:A 69@C >436;>=F A =5R 3F'&入口浓度表!中其他参数不变$改变床体入口氢浓度%-S %*+%%%*+-%%*)%%%*)-%%778&$对模型进行参数化扫描$考察氢浓度对穿透曲线的影响$并与实验结果进行对比$结果如图S 所示)由图S 可发现$模拟所得穿透曲线与实验所得穿透曲线线型和变化规律基本一致$在穿透拐点处数据存在一定偏差$验证了模型的准确性)因模型中床层温度设为恒温+%-Z $未考虑吸附热效应$图S 中模拟结果与试验数据拟合度较高$说明在入口浓度-S %#)%%%778范围内$吸附热基本被载气带走$吸附热效应对传质影响较小)入口浓度-S %778时$)%%8A 9内床体出口浓度几乎为%778$说明床体对氢气具有较高的吸附效率$随着入口氢浓度的增加$吸附效率下降$穿透提前出现)图(!床体径向长度方向浓度分布随入口氢浓度的变化N A E"(!Q 69@39:>=:A 69F A ?:>A R C :A 694=>A =:A 69A 9>=F A =5539E :<F A >3@:A 69X A :<A 953:6E39@69@39:>=:A 69不同入口氢浓度下吸附初期床体径向长度方向浓度分布如图(所示)从图(可发现$入口氢浓度对传质区长度影响较大)入口浓度为-S %778时$传质区长度较短$仅'c (88$随着入口浓度的增加$传质区长度逐渐增大$当入口浓度为)-%%778时$粉末层厚度刚好为!个传质区长度$初始出口浓度为%778$随后出口浓度增加$出现穿透)+&高径比床体粉末层体积保持T +c -*@8+$表!中其他参数不变$调整粉末层厚度$使高径比U 为'c %%*-c %T *(c ++*'+c !)%表'&后$对模型进行参数化扫描$考察高径比对穿透性能的影响$结果如图*所示)由图*可发现$随着高径比的增加$床体效率明显下降$其中高径比'c %%#(c ++时$维持高效率的时间较长)高径比为'+c !)时$维持高效率时间明显缩短)吸附初期$不同高径比下径向方向的浓度分布如图!%T(!原子能科学技术!!第-(卷所示)由图!%可发现$随着高径比的增加$传质区长度明显降低)虽然高径比增加$粉末层厚度会减小$而伴随着床体高度的增加$在保持入口流量一定的情况下$粉末层径向流速会减小$但传质区长度不是呈比例变化$导致高径比增加后床体出现提前穿透情况)考虑到粉末层厚度增加后床体的压阻也会增加$同时厚度越大$加热解吸时粉末层的均匀性问题越突出$在床体结构设计时$床体粉末层厚度推荐(#!-88$对应高径比为'c %%#(c ++)表D !径向床结构参数:,=-'D !.+(/4+/(,-&,(,)'+'(6"1(,!#,-='!粉末层厚度,88粉末层高度,88高径比%U &!-+%c %%'c %%!%-%c T +-c %T (T T c T !(c ++-!!-c S !'+c !)图*!高径比对径向吸附床穿透曲线的影响N A E"*!P 9;5C 39@36;U 697393:>=:A 69@C >436;>=F A =5=F ?6>7:A 69R 3F 图!%!高径比对径向方向浓度分布的影响N A E"!%!P 9;5C 39@36;U 69@69@39:>=:A 69F A ?:>A R C :A 69A 9>=F A =5F A >3@:A 69)&孔隙率表!中其他参数不变$调整粉末孔隙率为%c -'*%c -T *%c T %*%c T )*%c T ($考察孔隙率对床体穿透曲线的影响$结果如图!!所示)由图!!发现$孔隙率为%c -'时$吸附)%%8A 9内$一直保持较高的吸附效率$床体出口氢浓度几乎为%778$之后随着孔隙率的增加$床体吸附效率明显下降)分析原因可能是$床体孔隙率较大时$粉末层体积不变$则粉末填充层质量减小$气体与合金粉末层的有效接触面积减小$导致吸氢速率下降+同时孔隙率增大会使气体流阻减小$径向速度增大$最终导致穿透性能明显下降)吸附初期孔隙率为%c -'#%c T (时床体粉末层径向方向浓度分布如图!'所示)由图!'发现$孔隙率增加后$传质区长度由!%c !88增加至!)88)结合径向床压阻性能影响分析$考虑床层的吸附效率*压阻效应及粉末的装填难度$推荐装填孔隙率为%c -T #%c T ))图!!!初始孔隙率对径向吸附床穿透曲线的影响N A E "!!!P 9;5C 39@36;A 9A :A =576>6?A :I 69>=F A =5=F ?6>7:A 69R 3F 7393:>=:A 69@C >43图!'!孔隙率对径向方向浓度分布的影响N A E "!'!P 9;5C 39@36;76>6?A :I 69@69@39:>=:A 69F A ?:>A R C :A 69A 9>=F A =5F A >3@:A 69S(!第!期!!丁卫东等#径向流氦氢分离床穿透特性实验与模拟分析F!结论!&随着入口氢浓度及床体温度的升高$粉末层穿透性能下降)'&采用Q M&H M O耦合建立的穿透模型所得结果与实验结果符合较好$验证了模型的准确性)+&通过模型及参数分析得到了推荐特性参数#吸附温度控制在室温#+)+Z之间+床体粉末层厚度控制在(#!-88$对应高径比为'c%%#(c+++装填孔隙率为%c-T#%c T))参考文献!!"!罗德礼$陈长安$黄志勇$等"中国P J L U氦冷固态实验包层模块氚工艺系统设计!1""核聚变与等离子体物理$'%%T$'T%+&#'!S,''%"!'"!U P Q#$P J MP$Q P#&$P Q K L J J P#$W L/#&#J P 0$3:=5"J>A:A C83D:>=@:A69?I?:38?;6>:<3L C>673=9K Q O O,K Q$W J W&?!1""N C?A69H@A,39@3=9FJ3@<9656E I$'%%($-)%!&#!%S,!!'"!+"!Q P#&$P Q K L J J P#$/P J J PN$#P L O O M#$3: =5"Q69@37:C=5F3?A E96;:>A:A C83D:>=@:A69?I?,:38;6>:<3L C>673=9K Q$W:3?:R5=9a3:86F C53!1""N C?A69L9E A933>A9E=9F23?A E9$'%!'$(S%-,T&#T'%,T')"!)"!W o Z Z P,2L&L#$Q#O2L U M/P$$2L&#/0L 2$3:=5"L D73>A839:=5A943?:A E=:A696;[>Q6E3:,:3>R3F?=?@=9F A F=:37>6@3??;6>:<3:>A:A C83D:>=@:A69?I?:38?6;:<3L C>673=9:3?:R5=9a3:86F C53?!1""N C?A69H@A39@3=9F J3@<9656E I$'%!S$S!%)&#-'S,-+!"!-"!/M W G M&$H L P P Q K P H$H#J M H K PN"#R?6>7, :A69=9FF3?6>7:A696;6E39;>68A93>:E=?8A D:C>3?X A:<=[>+#5'7=>:A@53R3F!1""N C?A69L9E A933>A9E=9F23?A E9$!**-$'(#+T',+T T"!T"!/M W G M&$N G Z#2#H"#R?6>7:A69=9F F3?6>7:A696;6E39X A:<7=>:A@53R3F?6;343>=5`A>@69A C8=556I?!1""16C>9=56;/C@53=>&=:3>A=5?$!**%$!S-#'%*,'!S"!S"!/M W G M&$N G Z#2#H$J#/P&G U/"#R?6>7:A69R>3=a:<>6C E<6;6E39A?6:673?A9A93>:E=?8A D:C>3=9FF3?6>7:A69@<=>=@:3>A?:A@?X A:<[>/A=556I7=>:A@53R3F!1""16C>9=56;:<3O3??,Q68869&3:=5?$!*(T$!'+#T-,S)"!("!W o Z Z P,2L&L#$Q#O2L U M/P$$2L&#/0L 2$3:=5"L D73>A839:=5A943?:A E=:A696;[>Q6E3::3>R3F?=?@=9F A F=:37>6@3??;6>:<3:>A:A C83D:>=@:A69?I?:38?6;:<33C>673=9:3?:R5=9a3:&6F C53?!1""N C?A69H@A39@3=9F J3@<9656E I$ '%!S$S!%)&#-'S,-+!"!*"!乐红丽"金属氢化物的动力学模型对比分析!1""化学工程与装备$'%!)%!!&#T,("!!%"$#/0.$O P^"#>34A3X69a A93:A@86F35?=9F @6>>3?769F A9E=9=5I?A?83:<6F?;6>6E39:6>=E38=:3>A=5?!1""P9:3>9=:A69=516C>9=56;K I F>6E39L93>E I$'%!T$)!%)%&#!(%S',!(%(S" !!!"乐红丽"#W-型金属氢化物反应器研究!2""武汉#武汉工程大学$'%!-"!!'"&#.L U G$0U M O O&$H G$$L U\"K3=:=9F 8=??:>=9?;3>A983:=5A F3>3=@:A69R3F?# L D73>A839:=5=9F:<36>3:A@=5>3?C5:?!1""16C>9=56;:<3O3??,Q68869&3:=5?$!*(S$!+!%!,'&# '+-,'))"!!+"Q K P#/0KO$J H#P1K$Q K#/00&$3:=5"Q687=>A?696;=?A9E53E>=A9=@:A4=:3F@=>R69=9F@65C89=F?6>7:A69?I?:38!1""Q=>R69$'%%'$)%%!-&#'*'!,'*+%"((!原子能科学技术!!第-(卷!第-(卷第!期原子能科学技术V65"-($/6"! !'%')年!月#:68A@L93>E I H@A39@3=9FJ3@<9656E I1=9"'%')P*4"*'-O B U合金在非纯氦气环境中的高温腐蚀行为研究郑!伟! 何学东! 银华强! # 杜!斌! 李昊翔! 马!涛! 蒲!洋' 王尚军'%!"清华大学核能与新能源技术研究院$北京!!%%%()+'"中核能源科技有限公司$北京!!%%%(%&摘要 P9@6935T!S合金是高温气冷堆蒸汽发生器的候选材料$在反应堆超高温运行时可能会受到氦气中痕量杂质的腐蚀)为探究合金在高温堆环境中的腐蚀机理$本研究开展了P9@6935T!S合金在*(%d的非纯氦气中的腐蚀实验$对气相以及腐蚀行为进行了分析)通过化学热力学和动力学计算$阐明了合金脱碳的机理$并建立了碳迁移判定模型和脱碳反应预测模型$与实验数据有良好的一致性)在此基础上$研究了预氧化和温度对脱碳反应的影响)研究结果表明$即使杂质含量极低$也会诱发相关的腐蚀行为)降低运行温度可以有效避免合金脱碳$但预氧化的抗脱碳效果不理想)因此$极低杂质含量并非高温堆一回路净化目标$应该根据模型预测和实验分析来选择更加合理的杂质控制方案)关键词高温合金+非纯氦气+高温气冷堆+腐蚀+脱碳中图分类号 J O+)!文献标志码 #文章编号 !%%%,T*+!%'%')&%!,%!(*,%*!"# 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!88的矩形片$用砂纸打磨后$再采用!,8的金刚石抛光剂进行抛光)此后$样品在乙醇中超声脱脂$在空气中干燥$并使用电子表B !P *4"*'-O B U 合金的化学成分:,=-'B !3;')#4,-4")&"6#+#"*"1P *4"*'-O B U,--"0元素含量,b Q %c %-Q >'%c 'N 3!c '-/A 余量&9%c )T #5!c !+H A %c '(J A%c %!天平称重)图!显示了P 9@6935T !S 合金在接收状态下的金相显微组织$其晶粒度为!c -)图!!P 9@6935T !S 合金在接收状态下的金相显微图N A E "!!&3:=556E >=7<A @8A @>6E >=7<6;=?,>3@3A 43F P 9@6935T !S=556IB C D !实验环境为了专门研究高温合金在特定非纯氦气环境中的高温腐蚀行为$清华大学核能与新能源技术研究院开发了一套新的实验台架$其概念示意图如图'所示)该实验装置由非纯氦气配置模块和高温腐蚀模块组成$可以灵活地配置杂质含量在%#!%%%,R =>范围内的各种特定非纯氦气$检测精度高达77R 量级$且腐蚀温度可实现从室温到!'%%d 的准确控制)因此$本装置的腐蚀工况几乎可以匹配K J 0U 的所有运行工况)此外$高压储气罐的设计压力为(&$=$容积为S -%O $可供应上千小时实验所用气量%流速为'%O ,<&)除了非纯氦气配置的灵活性和大容量以外$该装置相较于购置标气而言还大幅降低了实验用气体的成本$具有很强的经济性)图'!非纯氦气环境下高温腐蚀系统设计示意图N A E "'!H @<38=:A @F >=X A 9E 6;?I ?:38F 3?A E9;6><A E <:3873>=:C >3@6>>6?A 69C 9F 3>A 87C >3<35A C 8=:86?7<3>3!*!第!期!!郑!伟等#P 9@6935T !S 合金在非纯氦气环境中的高温腐蚀行为研究。

吸附脱附曲线分析

吸附等温线‎- 概述吸附等温曲线是指在一定‎温度下溶质‎分子在两相‎界面上进行‎的吸附过程达到平衡‎时它们在两‎相中浓度之‎间的关系曲‎线。

在一定温度‎下,分离物质在‎液相和固相‎中的浓度关‎系可用吸附‎方程式来表‎示〔1〕。

作为吸附现‎象方面的特‎性有吸附量‎、吸附强度、吸附状态等‎,而宏观地总‎括这些特性‎的是吸附等‎温线〔2〕。

吸附等温曲‎线用途广泛‎,在许多行业‎都有应用。

在地质科学‎方面,可以用于基‎于吸附等温‎线的表面分‎形研究及其‎地球科学应‎用〔3〕;在煤炭方面‎,煤对混合气‎体中CH4‎和CO2的‎吸附呈现出不同的‎吸附特点;煤对CO2‎优先吸附,并且随着压‎力的升高,煤对CO2‎选择性吸附‎…吸附等温线‎- 吸附等温线‎平衡在恒定温度‎下，对应一定的‎吸附质压力‎，固体表面上‎只能存在一‎定量的气体‎吸附。

通过测定一‎系列相对压‎力下相应的‎吸附量，可得到吸附‎等温线。

吸附等温线‎是对吸附现‎象以及固体‎的表面与孔‎进行研究的‎基本数据，可从中研究‎表面与孔的‎性质，计算出比表‎面积与孔径‎分布。

吸附等温线‎有以下六种‎（图 1）。

前五种已有‎指定的类型‎编号，而第六种是‎近年补充的‎。

吸附等温线‎的形状直接‎与孔的大小‎、多少有关。

Ⅰ型等温线：Langm‎u ir 等温线相应于朗格‎缪单层可逆吸附过程，是窄孔进行‎吸附，而对于微孔‎来说，可以说是体‎积充填的结‎果。

样品的外表‎面积比孔内‎表面积小很‎多，吸附容量受‎孔体积控制‎。

平台转折点‎对应吸附剂‎的小孔完全‎被凝聚液充‎满。

微孔硅胶、沸石、炭分子筛等，出现这类等‎温线。

这类等温线‎在接近饱和‎蒸气压时，由于微粒之‎间存在缝隙‎，会发生类似‎于大孔的吸‎附，等温线会迅‎速上升。

Ⅱ型等温线：S 型等温线相应于发生‎在非多孔性‎固体表面或‎大孔固体上‎自由的单一‎多层可逆吸‎附过程。

在低P/P0处有拐‎点B，是等温线的‎第一个陡峭‎部,它指示单分‎子层的饱和‎吸附量，相当于单分‎子层吸附的‎完成。

N2吸脱附曲线说明

关于氮气等温吸脱附计算比表面积、孔径分布的若干说明我们拿到的数据，只有吸脱附曲线是真实的，比表面积、孔径分布、孔容之类的都是带有主观人为色彩的数据。

经常听到有同学说去做个BET，其实做的不是BET，是氮气等温吸脱附曲线，BET（Brunauer-Emmet-Teller）只是对N2-Sorption isotherm中p/p0=0.05~0.35之间的一小段用传说中的BET公式处理了一下，得到单层吸附量数据Vm，然后据此算出比表面积，如此而已。

◆六类吸附等温线类型几乎每本类似参考书都会提到，前五种是BDDT(Brunauer-Deming-Deming-Teller)分类，先由此四人将大量等温线归为五类，阶梯状的第六类为Sing增加。

那么吸附曲线在：低压端偏Y轴则说明材料与氮有较强作用力(І型，ІІ型，Ⅳ型)，较多微孔存在时由于微孔内强吸附势，吸附曲线起始时呈І型；低压端偏X轴说明与材料作用力弱(ІІІ型，Ⅴ型)。

中压端多为氮气在材料孔道内的冷凝积聚，介孔分析就来源于这段数据，包括样品粒子堆积产生的孔，有序或梯度的介孔范围内孔道。

BJH方法就是基于这一段得出的孔径数据；高压段可粗略地看出粒子堆积程度，如І型中如最后上扬，则粒子未必均匀。

平常得到的总孔容通常是取相对压力为0.99左右时氮气吸附量的冷凝值。

◆几个常数※液氮温度77K时液氮六方密堆积氮分子横截面积0.162平方纳米，形成单分子层铺展时认为单分子层厚度为0.354nm※标况（STP）下1mL氮气凝聚后（假定凝聚密度不变）体积为0.001547mL例：如下面吸脱附图中吸附曲线p/p0最大时氮气吸附量约为400 mL，则可知总孔容＝400*0.001547＝400/654＝约0.61mL※STP每mL氮气分子铺成单分子层占用面积4.354平方米例：BET方法得到的比表面积则是S/(平方米每克)＝4.354*Vm，其中Vm由BET方法处理可知Vm=1/(斜率＋截距)◆以SBA-15分子筛的吸附等温线为例加以说明此等温线属IUPAC 分类中的IV型，H1滞后环。

矿化垃圾固定床吸附过程和穿透曲线预测

Adsorption of phenols on an aged 2refuse f ixed 2bed and m odels for pred iction of breakthrough curves
ZHAO Tiantao
1, 2, 3
, ZHANG L ijie , QUAN Xuejun , ZHAO Youcai ,WANG Fup ing
基金项目 : 重庆市科技攻关项目 (No. 2005AC7107)
Supported by the Key Program of Science and Technology in Chongqing (No. 2005AC7107)
作者简介 : 赵天涛 ( 1976 —) ,男 ,讲师 (博士研究生 ) , E 2mail: zhaott@ cqit . edu. cn; 3 通讯作者 (责任作者 )
矿化垃圾作为一种生物吸附介质已被越来越多地应用于污水处理领域 ( Zhao et a l . , 2002;
2004 ) ,以矿化垃圾作为填充介质的生物反应床 , 具
有吸附容量大、生物总量多、接触时间长等特点 ( Zhao et a l . , 2007 ) . 相对于传统处理方法 , 矿化垃圾不仅在难降解有机物的去除及运行成本的节省方面具有较大优势 , 而且由于生物床可以将吸附和
1 引言 ( Introduction )
降解分阶段进行 ,从而可以实现比传统工艺更低的排放浓度 . 穿透曲线的预测是固定床吸附过程设计与操作的基础 (孙彦 , 2005 ) . 尽管很多模型可以用来预测穿透曲线 , 但大多过于复杂 ( Slaney et a l . , 1998; Tsai et a l . , 1999 ) , 不适于工程放大等应用 . 本研究中以固定床轴向扩散模型和等温吸附方程为理论基础 ( Roger et a l . , 2003 ) , 推导了穿透曲线的数学模型 ,并以工业废水中常见的苯酚和对氯苯酚作为

N2吸脱附曲线说明

经常听到有同学说去做个BET，其实做的不是BET，是氮气等温吸脱附曲线，BET（Brunauer-Emmet-Teller）只是对N2-Sorption isotherm中p/p0=0.05~0.35之间的一小段用传说中的BET公式处理了一下，得到单层吸附量数据Vm，然后据此算出比表面积，如此而已。

◆六类吸附等温线类型几乎每本类似参考书都会提到，前五种是BDDT(Brunauer-Deming-Deming-Teller)分类，先由此四人将大量等温线归为五类，阶梯状的第六类为Sing增加。

中压端多为氮气在材料孔道内的冷凝积聚，介孔分析就来源于这段数据，包括样品粒子堆积产生的孔，有序或梯度的介孔范围内孔道。

BJH方法就是基于这一段得出的孔径数据；高压段可粗略地看出粒子堆积程度，如І型中如最后上扬，则粒子未必均匀。

平常得到的总孔容通常是取相对压力为0.99左右时氮气吸附量的冷凝值。

◆几个常数※液氮温度77K时液氮六方密堆积氮分子横截面积0.162平方纳米，形成单分子层铺展时认为单分子层厚度为0.354nm※标况（STP）下1mL氮气凝聚后（假定凝聚密度不变）体积为0.001547mL例：如下面吸脱附图中吸附曲线p/p0最大时氮气吸附量约为400 mL，则可知总孔容＝400*0.001547＝400/654＝约0.61mL※STP每mL氮气分子铺成单分子层占用面积4.354平方米例：BET方法得到的比表面积则是S/(平方米每克)＝4.354*Vm，其中Vm由BET方法处理可知Vm=1/(斜率＋截距)◆以SBA-15分子筛的吸附等温线为例加以说明此等温线属IUPAC 分类中的IV型，H1滞后环。

N2吸脱附曲线说明

关于氮气等温吸脱附计算比表面积、孔径分布的若干说明观人为色彩的数据。

经常听到有同学说去做个BET，其实做的不是BET，是氮气等温吸脱附曲线，BET（Brunauer-Emmet-Teller）只是对N2-Sorption isotherm中p/p0=0.05~0.35之间的一小段用传说中的BET公式处理了一下，得到单层吸附量数据Vm，然后据此算出比表面积，如此而已。

◆六类吸附等温线类型几乎每本类似参考书都会提到，前五种是BDDT(Brunauer-Deming-Deming-Teller)分类，先由此四人将大量等温线归为五类，阶梯状的第六类为Sing增加。

中压端多为氮气在材料孔道内的冷凝积聚，介孔分析就来源于这段数据，包括样品粒子堆积产生的孔，有序或梯度的介孔范围内孔道。

BJH方法就是基于这一段得出的孔径数据；高压段可粗略地看出粒子堆积程度，如І型中如最后上扬，则粒子未必均匀。

平常得到的总孔容通常是取相对压力为0.99左右时氮气吸附量的冷凝值。

◆几个常数※液氮温度77K时液氮六方密堆积氮分子横截面积0.162平方纳米，形成单分子层铺展时认为单分子层厚度为0.354nm※标况（STP）下1mL氮气凝聚后（假定凝聚密度不变）体积为0.001547mL例：如下面吸脱附图中吸附曲线p/p0最大时氮气吸附量约为400 mL，则可知总孔容＝400*0.001547＝400/654＝约0.61mL例：BET方法得到的比表面积则是S/(平方米每克)＝4.354*Vm，其中Vm由BET方法处理可知Vm=1/(斜率＋截距)此等温线属IUPAC 分类中的IV型，H1滞后环。