BS-DTAB复配修饰红壤对苯酚的吸附

为了探究复配修饰后,可变电荷类型的红壤与恒电荷土壤对苯酚的吸附差异,以红壤作为供试土样,在两性表面活性剂BS-12(十二烷基二甲基甜菜碱)修饰的基础上,以阳离子型表面活性剂DTAB(十二烷基三甲基溴化铵)复配修饰制备两性-阳离子复配修饰红壤,采用批处理法研究在单一苯酚及Cd2+复合条件下供试土样对苯酚的吸附效果,并分析不同修饰比例、温度、离子强度和pH的影响。结果表明,DTAB复配修饰增强了BS-12两性修饰红壤对苯酚的吸附能力,单一苯酚表现出在总修饰比例小于150%CEC时吸附量随着修饰比例的增加而递增;各修饰土对苯酚的吸附具有增温负效应;苯酚吸附量随着pH的升高而降低;随着离子强度的增大,苯酚单一处理时供试土样对苯酚吸附量减少,但苯酚和Cd2+复合处理时,则呈现先降低后升高的趋势。Henry模型能较好地拟合各修饰红壤对苯酚吸附的等温吸附数据,吸附以分配机制为主;供试土样对苯酚的吸附属于自发的物理吸附过程。复配修饰红壤的苯酚吸附量低于恒电荷土壤,其黏土矿物成分决定的低CEC是主要影响因素。

Adsorption of phenol onto red soil modified with a BS-DTAB complex

To investigate the differences in adsorption of phenol between variable-charge red soil and constant-charge soil after organic complex modification, phenol adsorption via either phenol only or phenol+Cd²⁺ treatment onto variable-charge red soil modified by a mixture of amphoteric modifier, dodecyl dimethyl betaine(BS-12) and the cationic modifier dodecyltrimethylammonium bromide(DTAB) was tested in a batch experiment. The influence of total modifier ratio(TMR), temperature, ionic strength, and pH on the discrepancies in adsorption were studied. The results showed that phenol adsorption onto amphoteric-modified red soil was enhanced by DTAB and increased with an increase in modifier ratio for phenol only treatment when the TMR was within 150% of the CEC. The Henry equation was the best model for describing the phenol adsorption isotherm, demonstrating that the mechanism of phenol adsorption onto the red soil modified with the BSDTAB complex was controlled by the partition effect. The phenol adsorption decreased with increases in temperature, pH, and ionic strength, while an increase was appeared in phenol+Cd²⁺ mixture treatment with an increase in ionic strength. The adsorption of phenol onto BSDTAB-modified red soil was a spontaneous physical adsorption process and was lower than that onto constant-charge soil. The low CEC due to the clay mineral composition was the determining factor in controlling phenol adsorption onto the amphoteric-complex-modified red soil.