功能化枝状复合吸附材料的制备及吸附Cr(Ⅵ)的性能

Preparation of functional dendritic composite adsorbents and their adsorption properties for Cr(Ⅵ)

【目的】针对介孔分子筛的化学改性合成枝状复合吸附材料,研究其吸附性能对重金属废水治理具有现实意义。【方法】以介孔材料SBA-15为硅源,通过化学修饰方法合成树枝状化合物的复合吸附材料SBA-15-G_(3),并用巯基耦合剂巯基乙酸在SBA-15-G_(3)上嫁接巯基,成功合成功能化吸附材料SBA-15-G_(3)-SH。通过场发射扫描电子显微镜、能量色散X-射线光谱、傅里叶变换红外光谱、X射线衍射、Zeta电位分析和氮气吸附-脱附等温线等方法对材料的结构和物理化学性质进行了表征。通过SBA-15-G_(3)-SH对水溶液中铬离子[Cr(Ⅵ)]的吸附,研究了pH、时间、初始铬离子浓度、温度等对吸附性能的影响。分析SBA-15-G_(3)-SH吸附剂的吸附等温线、动力学和热力学特性,采用Langmuir和Freundlich吸附等温线模型对数据进行分析。【结果】Langmuir吸附等温线模型较好地拟合了吸附过程,吸附动力学模型符合准二级动力学方程。【结论】吸附主要通过SBA-15-G_(3)-SH表面的—SH基团表面络合作用以及与重金属离子的静电吸引,导致形成稳定的化合物。热力学结果表明:吸附Cr(Ⅵ)是一个自发的放热过程。

[Objective]The objective is to study the adsorption property of dendritic composite adsorbent synthesized by chemical modification of mesoporous molecular sieve for the treatment of heavy metal wastewater.[Method]The composite adsorbent SBA-15-G_(3) of dendritic compounds was synthesized by chemical modification with mesoporous material SBA-15 as silicon source,and the functional adsorbent SBA-15-G_(3)-SH was successfully synthesized by grafting sulfhydryl onto SBA-15-G_(3) with thioglycolic acid as coupling agent.The structure and physicochemical properties of the materials were characterized by field emission scanning electron microscopy(FESEM),energy dispersive X-ray spectroscopy(EDS),Fourier-transform infrared spectroscopy(FTIR),X-ray powder diffraction(XRD),Zeta potential analysis,and nitrogen adsorption-desorption isotherms(BET).The effects of pH,time,initial Cr(Ⅵ)concentration,and temperature on the adsorption properties were studied through the adsorption of Cr(Ⅵ)in aqueous solution by SBA-15-G_(3)-SH.The adsorption isotherms,kinetics and thermodynamic characteristics of SBA-15-G_(3)-SH adsorbent were analyzed.Langmuir and Freundlich adsorption isotherm models were used to analyze the experimental data.[Result]The Langmuir adsorption isotherm model fitted the adsorption process well,and the adsorption kinetic model accorded with the pseudo second-order kinetic equation.[Conclusion]The adsorption mainly results in the formation of stable compounds through the surface complexation of-SH group on the surface of SBA-15-G_(3)-SH and the electrostatic attraction of heavy metal ions.The thermodynamic results show that Cr(Ⅵ)adsorption onto SBA-15-G_(3)-SH is a spontaneous exothermic process.The high adsorption performance indicates that the SBA-15-G_(3)-SH is an efficient adsorbent to eliminate Cr(Ⅵ)from wastewater.[Ch,10 fig.3 tab.21 ref.]