季铵木质素对Cr(Ⅵ)的吸附

Adsorption of Cr(Ⅵ)by Quaternary Ammonium Lignin

采用稻草制备的季铵木质素对Cr(Ⅵ)进行吸附,通过对吸附前后季铵木质素的傅里叶红外光谱(FTIR)和X射线光电子能谱(XPS)分析吸附过程的机理,考察了Cr(Ⅵ)起始浓度、温度、时间和起始pH对吸附效果的影响。结果表明,Cr(Ⅵ)主要以HCrO_(4)^(-)形态被季铵和胺基吸附,部分被吸附后的HCrO_(4)^(-)被苯环上的烷基及酚羟基还原成Cr(Ⅲ)并被羧基吸附,少量Cr(Ⅵ)直接被电子官能团还原成Cr(Ⅲ)。当Cr(Ⅵ)起始浓度为50 mg/L、起始pH为1.08、120 min和25℃时,Cr(Ⅵ)去除率达到99.76%,吸附过程遵循准二级动力学和Langmuir模型,表明吸附过程为单分子层均质化学吸附。通过对季铵木质素吸附Cr(Ⅵ)的机理和行为研究,可以为稻草的资源化利用和铬的去除提供理论依据。

Cr(Ⅵ)was adsorbed by quaternary ammonium lignin prepared from straw.The mechanism of adsorption was revealed by FTIR and XPS analysis of quaternary ammonium lignin before and after adsorption.Effects of initial concentration of Cr(Ⅵ),temperature,time and initial pH value on adsorption were investigated.The results show that Cr(Ⅵ)is adsorbed mainly by quaternary ammonium and amino in the form of HCrO_(4)^(-).Part of adsorbed HCrO_(4)^(-)is reduced to Cr(Ⅲ)by alkyl groups and phenolic hydroxyl groups on the benzene ring and absorbed latter by carboxyl groups.A small amount of Cr(Ⅵ)is directly reduced to Cr(Ⅲ)by electron donating functional groups.When initial concentration of Cr(Ⅵ)is 50 mg/L,initial pH value is 1.08,adsorption time is 120 min and temperature is 25℃,the removal rate of Cr(Ⅵ)is 99.76%.The adsorption follows the quasi-second-order kinetics and Langmuir models,which indicates that the adsorption is monolayer homogeneous chemisorptions.The research on mechanism and behavior of Cr(Ⅵ)adsorption by quaternary ammonium lignin can provide theoretical basis for resource utilization of rice and removal of chromium.