两性-阴离子复配修饰对黄棕壤吸附Cd2+的影响

摘要

为了探究膨润土吸附Cd2+的最佳条件应用于实际土壤的可行性,在十二烷基二甲基甜菜碱(BS-12)和十二烷基磺酸钠(SDS)复配修饰膨润土对Cd2+吸附的最佳修饰比例基础上,制备了2个系列的BS-12+SDS复配修饰黄棕壤.通过X射线衍射和有机碳含量表征了黄棕壤的结构;研究了黄棕壤对Cd2+的吸附特征,分析了离子强度、pH和温度对黄棕壤吸附Cd2+的影响;讨论了黄棕壤与膨润土以及2种黄棕壤之间对Cd2+吸附的差异.结果表明,2种黄棕壤各修饰土层间距较未修饰土样变化不明显,有机碳含量随土样总修饰比例的增大而升高;复配修饰黄棕壤和膨润土相同,对Cd2+的吸附能力较两性及未修饰黄棕壤增强,30℃时吸附量呈现215BS+322SDS(215%BS-12+322%SDS)>215BS(215%BS-12)>CK1(43%蒙脱石含量黄棕壤),33BS+49SDS(33%BS-12+49%SDS)>33BS(33%BS-12)>CK2(6%蒙脱石含量黄棕壤);且Cd2+在2种黄棕壤复配修饰土中的解吸程度均高于CK和BS修饰土.Langmuir模型适合描述黄棕壤对Cd2+的吸附;膨润土对Cd2+吸附的最佳修饰比例应用到黄棕壤中,仍具有对Cd2+最佳吸附效果;黄棕壤修饰土对Cd2+的吸附,随离子强度的增大而减小,pH值对其影响不大,SDS复配修饰后,温度效应由CK、BS修饰土的升温正效应向BS+SDS修饰土的升温负效应转变,和膨润土吸附Cd2+规律相同;CEC是不同基质间吸附Cd2+产生差异的根本原因.%In order to explore the application of Cd2+ adsorption on yellow brown soils with the best modification ratio of adsorption of Cd2+ on bentonites, we prepared two series of yellow brown soils, modified by dodecyl dimethyl betaine (BS-12) and sodium dodecyl sulfonate (SDS), respectively. The structures of soils were characterized by X-ray diffraction and organic carbon contents. The adsorption properties and influence factors, such as ionic strength, pH and temperature were investigated. Furthermore, we also assessed the differences in Cd2+ adsorption between bentonites and two modified yellow brown soils. Compared with unmodified soils, the interlayer spacing in modified soils was not significantly changed and the total organic carbon content increased with increment of the total modification. Similar with bentonites, the adsorption of Cd2+ on co-modifiedyellow brown soils was stronger than that of BS modified soils and non-modified soils. At 30oC, the adsorption capacity was 215BS + 322SDS (215%BS-12 + 322%SDS) > 215BS (215%BS-12) > CK1 (soil containing montmorillonite content of 43%) and 33BS + 49SDS (33%BS-12 + 49%SDS) > 33BS (33%BS-12) > CK2 (soil containing montmorillonite content of 6%). In addition, the desorption of Cd2+ on co-modified yellow brown soils was higher than CK and BS modified yellow brown soils. Langmuir equation was suitable to describe the adsorption of Cd2+on yellow brown soil. Cd2+ could be effectively adsorbed by yellow brown soils with the best modification ratio of bentonites. The adsorption of modified yellow brown soils decreased with ionic strength rising. pH had little influence on Cd2+ adsorption. Similar with modified bentonites, the temperature effect changed from positive on CK and amphoteric soils to negative on BS+SDS soils after SDS modified. CEC contributed most to the adsorption difference of Cd2+.