HDTMA在蛭石插层的化学反应特性

Chemical Reaction Characteristics of HDTMA + Cations inInterlayer Space of Vermiculite Crystal LayersTongjiang Peng a,* , Hongjuan Sun b , Jinmei Sun c and Haifeng Liu d1Institution of Mineral Material & Application, Southwest University of Science & Technology,Mianyang 621010, P.R.Chinaa tjpeng@,b sunhongjuan@,c sunjinmei_1982@ ,d liuhaifeng@Keywords: hydrophlogopite, vermiculite, organic intercalation, arrangement modelAbstract. Hydrophlogopite, a regular interstratified mineral with 1:1 ratio of vermiculite and phlogopite crystal layers, was modified with sodium and organically intercalated with HDTMAB, and then the samples were examined with XRD. Based on the theoretical geometric dimensions of organic cations, the structure and arrangement model of HDTMA + cation in the interlayer space of vermiculite crystal layers were studied, the reaction mechanism of organic intercalation was also discussed. The results show that HDTMA + cations enter into the interlayer space of vermiculite crystal layers only without exchange with the cations in the interlayer space of phlogopite crystal layers, and that the arrangement models of HDTMA + cations in the interlayer space of vermiculite crystal layers varies with the added amount of HDTMAB. When the added amount is small, the arrangement model of HDTMA + cations in the interlayer space of vermiculite crystal layers is lateral-bilayer, and when the added amount is larger, the arrangement model is paraffin-type monolayer.1 IntroductionIndustrial vermiculite mineral is one of the non-metallic mineral products with potential advantages in China. The Xinjiang Weili Vermiculite Mine is the largest vermiculite Mine in China, accounting for 90% of the total industrial vermiculite reserves in the country. The industrial vermiculite mineral from this Mine consists of phlogopite-vermiculite interstratified mineral, mainly regular phlogopite-vermiculite 1:1 interstratified mineral, i.e., hydrophlogopite [1]. The interlayer space of phlogopite crystal layers is mainly filled with K + ions, and that of vermiculite crystal layers is mainly filled with the hydrated cations of Na +, Ca 2+, and K +, etc. The hydrated cations in the interlayer space of vermiculite crystal layers have good exchangeability, so organic hydrophlogopite and organic/inorganic nanometer composite materials can be prepared by cation exchange; the modified hydrophlogopite has been used in the field as, for example, a catalyst and carrier, waste water treating compound, and adsorbent, etc.Researchers have widely and deeply studied the preparation of organically intercalated clay minerals through utilizing quaternary ammonium salt. Zhu Jianxi et al. studied montmorillonite by using HDTMAB as intercalation agent, and found that the quaternary ammonium cations could be arranged into many arrangement models in the interlayer space, such as lateral-monolayer, lateral-bilayer, false three-layer, paraffin-type monolayer, and paraffin-type bilayer, and that there were different interlayer distances for each arrangement model [2,3]. Williams-Daryn, et al. researched the arrangement of the single-chained and double-chained quaternary ammonium cations in the interlayer space by using N-alkyl trimethyl ammonium bromide (N=10, 12, 16, 18) to treat Na-vermiculite; the results showed that the arrangement of the single-chained quaternary ammonium cations in the interlayer space was paraffin-type monolayer and that the arrangement ofthedouble-chained quaternary ammonium cations in the interlayer space depended on the structure of the short chains and the long chains [4,5]. Wu Pingxiao, et al. studied the organic intercalation of octadecyl trimethyl ammonium bromide into the mixture of hydrobiotite, vermiculite and phlogopite, and the results showed that when the added amount of octadecyl trimethyl ammonium bromide was small, the K+ ions in the biotite crystal layers of the hydrobiotite were not involved in an ion exchange reaction. However, when the added amount of octadecyl trimethyl ammonium bromide was large, the crystal layers of the biotite were also in a paraffin-type bilayer arrangement, and that the gradual change of arrangement models of the quaternary ammonium cations in the interlayer space was as follows: paraffin-type monolayer in vermiculite crystal layers → paraffin-type bilayer in vermiculite crystal layers → paraffin-type bilayer in vermiculite crystal layers and biotite crystal layers [6].The phlogopite-vermiculite interstratified mineral and hydrophlogopite are 2:1 type phyllosilicate minerals like montmorillonite, but the layer charge of vermiculite crystal layer is higher than that of montmorillonite so the ion exchange reaction with the organic ions is more difficult. The report regarding the study on the interaction of hydrophlogopite and the quaternary ammonium cations is rare. In this paper, we used hexadecyl trimethyl ammonium bromide (HDTMAB) to prepare organic hydrophlogopite, discussed the mechanism of intercalation, studied on the chemical reaction characteristics and the arrangement models of the organic cations in the interlayer of vermiculite.2 Experimental DetailsThe hydrophlogopite sample was taken from the Xinjiang Weili Vermiculite Mine, tabular crystal, color brown or gray, luster like grease, cleavage {001} perfect, cleavage flakes with flexibility but not elastic. The sample was ground to 200 mesh powder, its cation exchange capacity (CEC) was 74.15mmol/100g, and the exchanged ions were mainly Ca2+and Na+. The chemical composition ω(B)/%: SiO2 45.65, Al2O3 12.12, Fe2O3 5.97, MgO 25.15, CaO 1.75, Na2O 0.49, K2O 5.26. The intercalation agent used was hexadecyl trimethyl ammonium bromide(HDTMAB), CH3(CH2)15N(CH3)3Br, analytical reagent, content ≥99.0%.The main equipments used were a DF-101S intelligent heat-collection type thermostatic heating magnetic stirrer, a 78-1 type magnetic heating stirrer, a TDL-40B low-speed and high-capacity bench centrifuge, etc.It has been shown through other research that, under the same experimental conditions, the quaternary ammonium cations (HDTMA+) would displace the Na+ ions in the interlayer space first. For this reason, hydrophlogopite was initially treated with sodium before organic intercalation. And then the hydrophlogopite was organically intercalated with HDTMAB.The ground sample was soaked into 1 mol/L Na2CO3 solution for four days, stirring completely at a certain interval to ensure complete sodium treatment of the sample. The sample was then centrifugalized, washed, dried, and ground into a 200 mesh powder. Two grams of sodium treated sample were measured into each of 16 beakers, 80 ml distilled water were added into each, and stirred for 10 minutes to fully wet and disperse completely. HDTMAB equivalent was added to 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.5, 2, 3, 5, 10 times of the cation exchange capacity (CEC) of the sample into each beaker. The samples were left to react for two hours, held at a constant temperature for 0.5 hours, and cooled at room temperature. The precipitate was then filtered and washed (the filtrate was tested with 0.1 mol/L AgNO3 solution until it was clear without precipitate, i.e. free of Br-). Last, the product was dried at 80℃ to derive the organic hydrophlogopite sample. An XRD analysis on the prepared samples was conducted at the Analytical & Testing Center of the Southwest University of Science & Technology by using an X′pert MPD Pro Type X-ray diffractometer from Panalytical B. V. Netherlands. Experimental conditions were as follows: Cu target; tube voltage: 40 KV; tube current: 40 mA; DS: 1/32º; SS: 0.04 rad; scanning range: 2º~12º continuous.3 Results and DiscussionThe results from the XRD analysis of the samples are shown in Fig. 1. From the XRD pattern in Fig.1a, for the original hydrophlogopite sample, we can see that hydrophlogopite has three levels of basal reflection in the range of 2θ=2º~12º and the interplanar spacing is 28.10Å (d 001), 12.02Å (d 002) and 8.52Å (d 003), respectively, no other impurity peak appears.(a)(b)Fig.1 XRD Patterns of Original, Modified and Organically Intercalated Samples of HydrophlogopiteFrom Fig.1a, we can see that the d 001 value of the sodium treated hydrophlogopite sample changed to about 23Å. Compared with the original sample, the d 001 value of the sodium treated hydrophlogopite sample is reduced. There has been research [7, 8] showing that the Na + ions had strong dissociating power and good exchangeability and were easy to be exchanged. Although the ionic radius of Na + (r=1.02Å) is larger than that of Ca 2+ (r=1.00 Å ), and thus the interlayer spacing of sodium treated hydrophlogopite increases, Ca 2+ can adsorb two layers of polar water molecules due to its ionic potential (ratio of ionic electrovalence to ionic radius) ≥2 electrovalence/Å and Na + can only adsorb one layer of polar water molecules due to its ionic potential ≤ 2 electrovalence/Å; therefore the d 001 value decreases.From the Fig.1b, we can see that when the added amount of the quaternary ammonium salt is 0.05, 0.1, and 0.2 times of CEC, the peak value and peak position of d 001 of the organically treated samples changes greatly compared with the sodium treated samples, and the change range is 4~5Å. When theadded amount of the quaternary ammonium salt is 0.2 times of CEC, the peak position of d001 of the sample evidently shifts to a low angle and forms a wide and gentle composite peak and the d001value is 27~40Å. It can be seen that the overall trend of the d001 peak position shifts to a low angle with the increase of an added amount of quaternary ammonium salt and the average peak value is 27.49Å. From Figures 1c, 1d, we can see that when the added amount of quaternary ammonium salt is increased to 0.3~3 times of CEC, the strength and the half high width and the position of the d001 peak of the organically treated samples are apparently changes. With the increase of the added amount of the quaternary ammonium salt, the d001peak position of every sample changes as follows: the peak position shifts to a low angle successively; the peak shape changes sharp; the half high width reduces, and the d001 value increases significantly, reaching about 40Å.The organic intercalation process in interlayer space of vermiculite crystal layers is an ion exchange reaction process. In general, the quaternary ammonium salt with long alkyl chain is used as an organic intercalation agent for treating the sodium modified vermiculite sample, and the mechanism is: Na+-Vermiculite + HDTMAB → HDTMA+-Vermiculite + NaBr (1) The HDTMA+ cation has a permanent positive charge which is independent of the pH value, its one end is a hydrophilic group with the positive charge and other end is a neutral organic group which is hydrophobic. The HDTMA+ cation is changed into the interlayer space of vermiculite crystal layers due to the double action of Coulomb force and the van der Waals force.For the modified hydrophlogopite, the interplanar spacing d001 changes significantly, because the HDTMA+ cations entered into the interlayer space of vermiculite crystal layers through ion exchange and their bulk effect enlarged the interlayer spacing height. It was found through research[9] that when the added amount of the quaternary ammonium salt was sufficient, vermiculite could adsorb the HDTMA+cations exceeding its CEC, which entered into vermiculite’s interlayer space mainly through the mechanism of molecular adsorption.Generally, when the added amount of the quaternary ammonium salt is small, the organic intercalation reaction of vermiculite is mainly ion exchange. For the HDTMA+ cations that entered into the interlayer space of vermiculite crystal layers through ion exchange, the hydrophilic group with the positive charge was adsorbed on the surface of the structural layer having negative charges of vermiculite crystal layers, and the neutral organic group was out and away from the surface of vermiculite’s structural layer. When the added amount of the quaternary ammonium salt was large, the quaternary ammonium salts could enter into the interlayer space of vermiculite not only through ion exchange but also via the molecule adsorption. The HDTMA+ cations entering into the interlayer space of vermiculite crystal layers are arranged into different arrangement models and change the thickness of vermiculite’s crystal layers.Through research on the FT-IR of organic intercalated montmorillonite, Vaia et al. [10] thought that HDTMA+cations in the interlayer space of montmorillonite had a wide range of molecular arrangement from solid-like to liquid-like. For the former, the alkyl chains were all-trans, and for the latter, they were attained by formation of gauche-bonds. The long alkyl chains were arranged more complicatedly in the interlayer space of montmorillonite, and the HDTMA+cations could be arranged in the interlayer space of montmorillonite in the models like lateral-monolayer, lateral-bilayer, paraffin-type monolayer, false three-layer, and paraffin-type bilayer, etc.Together with the van der Waals radius, covalent bond and bond angle data, we can achieve the spatial configuration, size and shape of the HDTMA+cation. For the stretching linear paraffin C n H2n+2, the C-C included angle is 109º28′, the C-C bond length is 0.154nm, the van der Waals radius of -CH3 is 0.2nm, and the C-N bond length is 0.147nm. The length of a single carbochain HDTMA+ cation can be calculated from the following formula [11]:L= (n-3)*0.154*cos35º+0.2*2+0.147 (2) Where L - length of HDTMA+ cation (nm); n - number of carbon atoms.The alkyl chain of HDTMA+ cation is approximately an elliptical cylinder of which the section has a 0.46 nm major axis and a 0.41 nm minor axis. The length of the fully stretching cation is about 2.5 nm.For the study of the spatial arrangement model of organic molecules/cations in the interlayer space, there is no relatively direct observation method currently available. However, we can derive the arrangement model of organic cations or organic molecules in the interlayer space from the geometric dimensions of the organic cations or organic molecules, as well as the XRD data from organically intercalated vermiculite and the crystal structure of vermiculite.Because the cations in the interlayer space of phlogopite crystal layers in hydrophlogopite do not have exchangeability, the K+ ions in the interlayer space of phlogopite crystal layers are not involved in ion exchange reaction. However the hydrated cations in the interlayer space of vermiculite crystal layers have exchangeability, so only the hydrated cation layers (i.e. Na+ ions and water molecules) in the interlayer space of vermiculite crystal layers are involved in the ion exchange reaction during the organic treatment reaction. Thus, the height of the HDTMA+ cation in the interlayer space is equal to the measured d001value minus the thickness of vermiculite crystal layer (0.93nm [12]) and the thickness of phlogopite crystal layer (1.0nm [12]), i.e. the height of the HDTMA+ cations is (d001 - 0.93 - 1.0) nm.Tomasz Kwolek et al. [13], through research on the isotherm adsorption of the short chain alkyl quaternary ammonium salt intercalated montmorillonite, found that the short chain alkyl quaternary ammonium ions are arranged in the interlayer space of the montmorillonite in the lateral model, and that when the carbon atom number of carbochain is more than 8, a cross bilayer structure, i.e. interlocking lateral-bilayer arrangement forms. The overall height will reduce about 0.1nm [2] for each layer of such an interlocking arrangement. So the height of the HDTMA+ cations in the lateral-bilayer arrangement model is 0.46*2 - 0.1=0.82nm. When the added amount of the quaternary ammonium salt is 0.05, 0.1, and 0.2 times of CEC (Figure 1b), the average d001value of the organically treated samples is 27.49Å and the calculated average height of the HDTMA+ cations in the interlayer space is 0.819nm, which highly matches the height of the organic phase with this lateral-bilayer arrangement model, so the HDTMA+ cations are arranged in a lateral-bilayer arrangement model in the interlayer space of vermiculite crystal layers.When the added amount of the quaternary ammonium salt is increased to 0.3~3 times of CEC (Figure 1c), the d001 value of the organically treated samples evidently increases, which is about 40Å, and the calculated height of the HDTMA+ cations is about 2.0nm, which is less than the length of the HDTMA+ cations. This shows that the HDTMA+ cations can only be arranged in the paraffin-type monolayer in the interlayer space of vermiculite crystal layers. According to the length of the straight chain of HDTMA+ cation, the thicknesses of a vermiculite crystal layer and a phlogopite crystal layer, and the d001 value from the organically treated samples, the included angle θ between the HDTMA+ cation and the surface of silica layer can be calculated.Table1 Added Amount of the HDTMA+Cation and Some Data of Organically Intercalated Hydrophlogopite SamplesAdded Amount of QuaternaryAmmonium Salt/CEC0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.5 2 3d001/Å 38.3740.1240.5641.4540.6240.3240.3540.1141.0539.4740.39Height of the HDTMA+ cation in Interlayer Space (/Å) 19.0720.8221.2622.1521.3221.0221.0520.8121.7520.1721.09The inclined angle of the HDTMA+ cation in interlayer space θ/° 49.7156.3958.2662.3858.5257.2257.3556.3560.4653.7857.52Table 1 shows the inclined angle of the HDTMA+ cation in the interlayer space of the organically treated samples, which is about 55º (from 49.71°~62.38°). Williams-Daryn et al. [4, 5] concluded that the best inclined angle of the HDTMA+ cation to the silicate structural layer is 54.5º, because this angle is most advantageous for the methyl group to maintain the largest contact area with the surface of the silicate structural layer. The inclined angle of the HDTMA+ cation in the interlayer space of thetested samples is closer to the angle 54.5º. This shows that when the added amount of the quaternary ammonium salt is 0.3~3 times of CEC, the HDTMA+cations in the interlayer space of the vermiculite crystal layers in hydrophlogopite are arranged in a paraffin-type monolayer model, which is a stable arrangement model with the highest probability4 ConclusionsAfter hydrophlogopite is sodium treated, the d001 value of the main diffraction peak changes from 28Å to about 23Å; this change mainly relates to the change in the number of water molecule layers in the interlayer space resulting from the changed cations.During the organic treatment, ion exchange reaction does not occur between HDTMA+ cations and the K+ cations of interlayer space of phlogopite crystal layers and only occurs between HDTMA+ cations and the Na+ cations of interlayer space of vermiculite crystal layers in hydrophlogopite.The arrangement model of HDTMA+ cations in the interlayer space of the vermiculite crystal layers in hydrophlogopite relates to the added amount of the quaternary ammonium salt. When the added amount of the quaternary ammonium salt is 0.05~0.2 times of CEC, the HDTMA+cations are arranged in lateral-bilayer model; and when the added amount of the quaternary ammonium salt is 0.3~3 times of CEC, the HDTMA+ cations are arranged in a paraffin-type monolayer model and the inclined angle is about 55°. In summary, with the increase of the added amount of the quaternary ammonium salt, the stacking density of the HDTMA+ cations in the interlayer space increases; this leads to the change in the arrangement model of the HDTMA+ cations in the interlayer space of the vermiculite crystal layers and the change trend is: lateral-bilayer → paraffin-type monolayer. Acknowledgement: The authors are grateful for the financial support from National Natural Science Foundation of China (40502008).References[1] Tongjiang Peng, Fusheng Liu, John Huang,et al.: Acta Petrologica Et Mineralogica, Vol. 22(2003), p. 391[2] Jianxi Zhu, Hongping He and Jiugao Guo: Journal of Mineralogy and Petrology, Vol. 23 (2003), p.1.[3] Jianxi Zhu, Hongping He and Jiugao Guo: Chinese Science Bulletin, Vol. 48 (2003), p. 302.[4] D.S.Williams and R.K.Thomas: Journal of Colloid and Interface Science, Vol. 255 (2002), p. 303.[5] S. Williams-Daryn, R. K. Thomas, M. A. Castro, et al.: Journal of Colloid and Interface Science,Vol. 256 (2002), p. 314.[6] Pingxiao Wu, Nengwu Zhu, Zhi Dang, et al.: Journal of Functional Materials, Vol. 37 (2006), p.83.[7] A.V.Faridi and S.Guggenheim: Clays and Clay Minerals, Vol. 45 (1997), p. 859.[8] P.G.Slade and W.P.Gates: Applied Clay Science, Vol. 25 (2004), p. 93.[9] A.Czimerova, J.Bujdak and R.Dohrmann: Applied Clay Science, Vol. 2 (2006), p. 1.[10] R.A.Vaia, P.K.Teukolsky and E.Giannelis:Chem Mater, Vol. 6 (1994), p. 1017.[11] Lu Xianjun, Song Meining and Qiu Jun: Non-ferrous Mining and Metallurgy, Vol. 21 (2005), p.89.[12] Naixian Zhang, Youqin Li, Huimin Zhao, et al.: Methods for Research on Clay Mineral (SciencePublications, China 1990).[13] Tomasz Kwolek, Maciej Hodorowicz, Katarzyna Stadnicka, et al.: Journal of Collold andInterface Science, Vol. 264 (2003), p. 14.Advance in Ecological Environment Functional Materials and Ion Industry10.4028//AMR.96Chemical Reaction Characteristics of HDTMA⁺ Cations in Interlayer Space of Vermiculite Crystal Layers10.4028//AMR.96.15DOI References[2] Jianxi Zhu, Hongping He and Jiugao Guo: Journal of Mineralogy and Petrology, Vol. 23 (2003), p.doi:10.1007/BF03183232[3] Jianxi Zhu, Hongping He and Jiugao Guo: Chinese Science Bulletin, Vol. 48 (2003), p. 302.doi:10.1007/BF03183232[4] D.S.Williams and R.K.Thomas: Journal of Colloid and Interface Science, Vol. 255 (2002), p. 303.doi:10.1006/jcis.2002.8673[5] S. Williams-Daryn, R. K. Thomas, M. A. Castro, et al.: Journal of Colloid and Interface Science, Vol. 256 (2002), p. 314.doi:10.1006/jcis.2002.8685[7] A.V.Faridi and S.Guggenheim: Clays and Clay Minerals, Vol. 45 (1997), p. 859.doi:10.1346/CCMN.1997.0450610[8] P.G.Slade and W.P.Gates: Applied Clay Science, Vol. 25 (2004), p. 93.doi:10.1016/j.clay.2003.07.007[9] A.Czimerova, J.Bujdak and R.Dohrmann: Applied Clay Science, Vol. 2 (2006), p. 1. doi:10.1016/S1572-4352(06)02001-0[10] R.A.Vaia, P.K.Teukolsky and E.Giannelis: Chem Mater, Vol. 6 (1994), p. 1017.doi:10.1021/cm00043a025[13] Tomasz Kwolek, Maciej Hodorowicz, Katarzyna Stadnicka, et al.: Journal of Collold and Interface Science, Vol. 264 (2003), p. 14.doi:10.1016/S0021-9797(03)00414-4。