苯酚在BS-Tw80复配修饰膨润土和高岭土上吸附的比较

以不同阳离子交换量(CEC)的膨润土和高岭土为基质,采用两性表面修饰剂十二烷基二甲基甜菜碱(BS-12)+非离子表面修饰剂吐温80(Tw80,T)进行复配修饰,以批处理法对比研究了不同修饰比例、温度、离子强度和pH条件下,两性复配修饰膨润土和高岭土对苯酚吸附的效果,并从吸附等温线、温度效应和热力学角度探讨比较了吸附机制.结果表明,土样CEC是影响复配修饰土样对苯酚吸附的关键因素,相同比例两性复配修饰的膨润土对苯酚吸附量均高于高岭土.不同因素对于复配修饰膨润土和高岭土吸附苯酚的影响总体具有良好的一致性,复配修饰均显著增强了膨润土和高岭土对苯酚的吸附能力,两种不同基质的50倍CEC的BS-12修饰基础上不同碳碳比例 Tw80(50BS+T)修饰土样随Tw80修饰比例加大对苯酚吸附量增大,100倍CEC的BS-12修饰基础上不同碳碳比例 Tw80(100BS+T)修饰土样随Tw80修饰比例加大对苯酚吸附量降低,复配修饰两种吸附基质对苯酚吸附量均随着温度、pH的升高而降低,随着离子强度的增大而升高.Henry模型适用于描述苯酚在各供试土样的吸附.BS+T复配修饰膨润土对苯酚的吸附决定于焓减和熵增,是多种吸附形式并重的吸附机制,而BS+T复配修饰高岭土是焓减决定的以疏水分配吸附为主的吸附机制.

Comparison of Phenol Adsorption on Bentonite and Kaolinite Co-modified by BS-12 and Tween-80

Clay minerals modified by different types of surfactants have showed enhanced capability of remediating soil or water polluted by heavy metals and organic substances. An experiment was designed to compare the adsorption of phenol on bentonite and kaolinite co-modified by dodecyl dimethyl betaine(BS-12)+ Tween80(Tw80, T) at different ratios of modifiers, ionic strength, temperature and pH using batch experiments. The adsorption mechanisms were explored by adsorption isotherms, temperature effects and thermodynamics. Results showed that CEC was the main factor influencing adsorption of phenol on co-modified clays. At the same ratio of the modifiers, bentonite with high CEC adsorbed more phenol than kaolinite with low CEC. The adsorption of phenol on modified bentonite and kaolinite showed consistent trends under different factors. The adsorption capacity of bentonite and kaolinite co-modified by BS-12+Tw80 was obviously higher than unmodified clays. It was found that the adsorption capacity of bentonite and kaolinite modified by 50BS+T increased with increasing Tw80 ratios, while that by 100BS+T decreased with increasing Tw80 ratios. The adsorption of phenol decreased with increasing temperature and pH, but increased with increasing ionic strength. Henry model very well described the adsorption of phenol. The adsorption of phenol on bentonite modified by BS+T was characteristized by enthalpy decreases and entropy increases, showing different forms of adsorption process, whereas the adsorption of phenol by kaolinite modified by BS+T was a hydrophobic adsorption process drived by enthalpy decreases.