BS-CTMAB复配修饰膨润土对苯酚的吸附

Adsorption of Phenol on Amphoteric-Cationic Modified Bentonites

采用两性表面修饰剂十二烷基二甲基甜菜碱（BS-12）和阳离子表面修饰剂十六烷基三甲基溴化铵（CTMAB）复配修饰膨润土，通过批处理法研究了不同修饰比例、温度、pH和离子强度等条件下，复配修饰膨润土对苯酚的吸附规律和热力学特征，并探讨了其吸附机制。结果表明，CTMAB复配修饰显著增强了两性修饰膨润土对苯酚的吸附能力，30℃时吸附量呈现100BS＋100CT（100％BS-12＋100％CTMAB）〉100BS＋50CT（100％BS-12＋50％CTMAB）〉50BS＋100CT（50％BS-12＋100％CTMAB）〉100BS＋150CT（100％BS-12＋150％CTMAB）〉50BS＋50CT（50％BS-12＋50％CTMAB）〉100BS＋25CT（100％BS-12＋25％CTMAB）〉50BS＋150CT（50％BS-12＋150％CTMAB）〉50BS＋25CT（50％BS-12＋25％CTMAB）〉100BS（100％BS-12）〉50BS（50％BS-12）〉CK（原土）的顺序。当CTMAB复配修饰比例在0~100％CEC时，两性复配修饰土样对苯酚的吸附量随着修饰比例的增大而升高，而在100％~150％CEC阶段，吸附量则随CTMAB修饰比例的增大有所降低；修饰土样对苯酚吸附量随着温度、pH的升高而降低，在低浓度范围内，随着离子强度的增大而升高。Henry模型适用于描述苯酚在供试土样的吸附，供试土样对苯酚的吸附属于自发的物理吸附过程，吸附呈现焓减、熵增特征。

Modified bentonites have been used as an adsorbent for environmental remediation. An experiment was designed to examine the adsorption of phenol on bentonites modified by a mixture of amphoteric modifier, dodecyl dimethyl betaine（BS-12）, and cationic modifier, hexadecyltrimethylammonium bromide（CTMAB）as influenced by modifier ratios, ionic strength, temperature and pH. Adsorption capacity of phenol on bentonites was in order of 100BS＋100CT（100%BS-12＋100%CTMAB）〉100BS＋50CT（100%BS-12＋50%CTMAB）〉50BS＋100CT（50%BS-12＋100%CTMAB）〉100BS＋150CT（100%BS-12＋150%CTMAB）〉50BS＋50CT（50%BS-12＋50%CTMAB）〉100BS＋25CT （100%BS-12＋25%CTMAB）〉50BS＋150CT（50%BS-12＋150%CTMAB）〉50BS＋25CT（50%BS-12＋25%CTMAB）〉100BS（100%BS-12）〉50BS（50%BS-12）〉CK（unmodified soil）. This revealed that the adsorption of phenol on modified bentonites increased with increasing CTMAB ratios at 0~100%of CEC, while decreased slightly at CTMAB ratios greater than 100%of CEC. The phenol adsorption was reduced by elevated temperature and pH, but increased with ionic strength at low concentration ranges. Henry equation could best describe the phe-nol isotherms. The adsorption of phenol on amphoteric-cationic modified bentonites is a spontaneous physical adsorption process character-istized by both enthalpy decreases and entropy increases.