Barczyk K, Mozgawa W, Król M
Faculty of Material Science and Ceramics, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Kraków, Poland.
Faculty of Material Science and Ceramics, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Kraków, Poland.
Spectrochim Acta A Mol Biomol Spectrosc. 2014 Dec 10;133:876-82. doi: 10.1016/j.saa.2014.06.065. Epub 2014 Jun 19.
This work presents results of FT-IR spectroscopic studies of anions-chromate, phosphate and arsenate - sorbed from aqueous solutions (different concentrations of anions) on zeolites. The sorption has been conducted on natural zeolites from different structural groups, i.e. chabazite, mordenite, ferrierite and clinoptilolite. The Na-forms of sorbents were exchanged with hexadecyltrimethylammonium cations (HDTMA(+)) and organo-zeolites were obtained. External cation exchange capacities (ECEC) of organo-zeolites were measured. Their values are 17mmol/100g for chabazite, 4mmol/100g for mordenite and ferrierite and 10mmol/100g for clinoptilolite. The used initial inputs of HDTMA correspond to 100% and 200% ECEC of the minerals. Organo-modificated sorbents were subsequently used for immobilization of mentioned anions. It was proven that aforementioned anions' sorption causes changes in IR spectra of the HDTMA-zeolites. These alterations are dependent on the kind of anions that were sorbed. In all cases, variations are due to bands corresponding to the characteristic Si-O(Si,Al) vibrations (occurring in alumino- and silicooxygen tetrahedra building spatial framework of zeolites). Alkylammonium surfactant vibrations have also been observed. Systematic changes in the spectra connected with the anion concentration in the initial solution have been revealed. The amounts of sorbed CrO4(2-), AsO4(3-) and PO4(3-) ions were calculated from the difference between their concentrations in solutions before (initial concentration) and after (equilibrium concentration) sorption experiments. Concentrations of anions were determined by spectrophotometric method.
这项工作展示了对从水溶液（不同阴离子浓度）中吸附在沸石上的阴离子——铬酸根、磷酸根和砷酸根进行傅里叶变换红外光谱（FT-IR）研究的结果。吸附实验采用了来自不同结构族的天然沸石，即菱沸石、丝光沸石、镁碱沸石和斜发沸石。将吸附剂的钠型与十六烷基三甲基铵阳离子（HDTMA(+)）进行交换，从而得到有机沸石。测定了有机沸石的外部阳离子交换容量（ECEC）。菱沸石的ECEC值为17mmol/100g，丝光沸石和镁碱沸石为4mmol/100g，斜发沸石为10mmol/100g。所使用的HDTMA初始投入量分别相当于这些矿物ECEC的100%和200%。随后，将有机改性吸附剂用于固定上述阴离子。结果表明，上述阴离子的吸附会导致HDTMA-沸石的红外光谱发生变化。这些变化取决于所吸附阴离子的种类。在所有情况下，变化都是由于对应于特征Si-O(Si,Al)振动的谱带（出现在构成沸石空间骨架的铝氧和硅氧四面体中）引起的。同时也观察到了烷基铵表面活性剂的振动。还揭示了光谱随初始溶液中阴离子浓度的系统性变化。吸附的CrO4(2-)、AsO4(3-)和PO4(3-)离子的量通过吸附实验前后溶液中它们的浓度（初始浓度和平衡浓度）之差来计算。阴离子浓度通过分光光度法测定。
