Abstract:

In presence of the attapulgite, the absorbent carboxymethyl cellulose-g-poly(acrylic acid)/acrylamide /attapulgite (CMC-g-PAA/AM/ATP) was synthesized by solution grafting copolymerization of carboxymethyl cellulose, acrylic acid and acrylic amide with ammonim peroxodisulphate as an initiator and MBA as crosslink agent. CMC-g-PAA/AM/ATP was applied in the Cd(II) adsorption from aqueous solution. The influences of pH, initial Cd(II) concentration, reaction time, temperature and dosage on the adsorption were investigated. The adsorption capacity reached a high level when pH was in the range of 4.0-8.0. The reaction reached equilibrium within 40 min and the adsorption kinetics was better described by pseudo-second order equation. The reaction was an exothermic process. The as-prepared and Cd-loaded CMC-g-PAA/AM/ATP were characterized by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) to identify the structure of the adsorbents, and verify the removal mechanisms. CMC-g-PAA/AM/ATP proved to be a promising candidate for the fast removal of Cd(II) from aqueous solution. The Cd(II) removal mechanisms by CMC-g-PAA/AM/ATP include electrostatic interaction, chelation and ion exchange.

Key words: CMC-g-PAA/ATP, Cd(II), adsorption, mechanisms

摘要：

在凹凸棒黏土(ATP)的存在下, 以羧甲基纤维素(CMC)为主链, 过硫酸铵(APS)作为引发剂, 以N,N-亚甲基双丙烯酰胺(MBA)作交联剂, 与丙烯酸(AA)和丙烯酰胺(AM)进行接枝共聚, 合成羧甲基纤维素?接枝?聚丙烯酸/丙烯酰胺/凹凸棒黏土(CMC-g-PAA/AM/ATP)复合水凝胶。采用该种材料吸附去除水体中的 Cd(Ⅱ), 考察溶液初始pH、金属离子浓度、反应时间、反应温度、吸附剂投加量等因素对吸附反应的影响, 并借助傅里叶转换红外光谱(FT-IR)和X射线光电子能谱(XPS)探究吸附机理。结果表明, 初始pH 范围在4.0~8.0内吸附效果佳, 吸附反应在40分钟内达到平衡, 整个吸附过程更符合准二级动力学模型, 吸附过程中放热。CMC-g-PAA/AM/ATP可以快速、有效地去除水溶液中的 Cd(II), 吸附机理包括静电作用、络合作用和离子交换作用。

关键词: CMC-g-PAA/AM/ATP, Cd(II), 吸附, 机理