阳离子型可逆表面活性剂在膨润土上的吸附行为

Sorption behavior of reversible cationic surfactant on bentonite

研究可逆表面活性剂十一烷基二茂铁三甲基溴化铵(FTMA)在膨润土上的吸附机理,并与CTAB进行对比;同时考察土壤关键因子对FTMA吸附的影响.结果表明,FTMA与CTAB在膨润土上的吸附变化规律一致,饱和吸附量为66cmol/kg,约为膨润土1倍CEC,吸附机制主要为阳离子交换作用.不同温度下FTMA吸附等温线均可用Langmuir模型描述,吸附量随温度升高(298→318K),由280.6mg/g增大至350.8mg/g.吸附在8h达到平衡,吸附速率较CTAB慢,并符合准二级动力学方程,化学吸附是主要控制速率步骤.热力学参数计算得出,该吸附是自发吸热过程.随体系离子强度的增大,吸附量下降;共存阳离子对吸附有抑制作用,且影响程度大小为:Ca2+>K+>Na+;pH值对吸附影响较小;腐植酸(HA)的加入促进了FTMA的吸附.

Thesorption mechanism of reversible cationic surfactant （11-ferrocenylundecyl） trimethylammonium bromide （FTMA） on bentonite was studied, and compared with CTAB; the effects of the key factors of soil on sorption were also studied. Results show that, sorption variation of FTMA is consistent with CTAB, the saturated sorption capacity of FTMA is 66cmol/kg, about one times CEC of bentonite, it suggests that cation exchange is the main sorption mechanism. The isotherms of FTMA all can be described with Langmuir model at different temperature, and the sorption capacity increases from about 280.6mg/g at 298K to about 350.8mg/g at 318K. The sorption of FTMA reaches equilibrium at 8h, the sorption rate is slower than CTAB, and fits Lagergren quasi-second-order kinetics equation, chemical sorption process is the main step of controlling rate. The sorption process is spontaneous and endothermic through thermodynamic parameters calculated. In addition, sorption capacity of FTMA decreases with ionic strength increasing; the sorption is inhibited by coexisting cations, and following order： Ca^2〉K^＋〉Na^＋; the impact of pH is slight and the addition of humic acid （HA） promotes the sorption of FTMA.