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采用低温回流法制备凹凸棒石/CoFe_2O_4磁性复合材料,利用比表面积(BET)、磁滞回线、红外光谱(FTIR)等手段对磁性复合材料进行表征,并研究磁性复合材料对Cr(Ⅵ)的吸附性能,利用吸附前后FTIR和光电子能谱(XPS)对其吸附机理进行初步探讨。结果表明,磁性复合材料的比表面积为175.85 m~2·g~(-1),略大于凹凸棒石;饱和磁化强度为14emu·g~(-1),易于磁分离。pH在2~12范围内,吸附量随pH值的增大而减小。Freundlich等温吸附模型能较好描述吸附实验结果。ΔG为-15.19~-14.28 k J·mol~(-1),ΔH为-19.15 k J·mol~(-1),ΔS为-13.96~-14.20 J·(mol·K)~(-1),说明该吸附是自发、放热的,低温有利于吸附;动力学实验表明吸附行为符合准二级动力学。由吸附前后的FTIR可知凹凸棒石/CoFe_2O_4中羟基参与Cr(Ⅵ)吸附过程;XPS分析可知吸附过程包含Cl~-与铬酸根的离子交换和Cr(Ⅵ)还原为Cr(Ⅲ)的反应。
The attapulgite / CoFe_2O_4 magnetic composites were prepared by low temperature reflow method. The magnetic composites were characterized by BET, Hysteresis loop and FTIR. The effects of magnetic composites on the Cr (Ⅵ) The adsorption mechanism of FTIR and photoelectron spectroscopy (XPS) before and after adsorption was discussed. The results show that the magnetic composite has a specific surface area of 175.85 m 2 · g -1, slightly larger than that of attapulgite, and its saturation magnetization is 14emu · g -1, which makes it easy to separate magnetically. The pH ranged from 2 to 12, and the adsorption capacity decreased with the increase of pH. Freundlich adsorption isotherm model can better describe the adsorption experiment results. ΔG was -15.19 ~ -14.28 kJ · mol -1, ΔH was -19.15 kJ · mol -1, ΔS was -13.96 ~ -14.20 J · mol -1, , Indicating that the adsorption is spontaneous and exothermic, low temperature is conducive to adsorption; kinetics experiments show that adsorption behavior in line with quasi-second-order kinetics. The FTIR results showed that the hydroxyl groups of attapulgite / CoFe2O4 were involved in the adsorption process of Cr (VI). XPS analysis showed that the adsorption process consisted of the ion exchange of Cl ~ - and chromate and the reduction of Cr (VI) to Cr (¢ ó).