BS-Tween20复配修饰膨润土对Cd^(2+)吸附的研究  

Cd^(2+) ADSORPTION OF BS-TWEEN20 COMPOUNDED MODIFIED BENTONITE

作　　者：马麟莉 孟昭福[1] 杨淑英[2] 杨亚提[2] 王建涛[1] 李彬[2] 

机构地区：[1]西北农林科技大学资源环境学院,陕西杨凌712100 [2]西北农林科技大学理学院,陕西杨凌712100

出　　处：《土壤学报》2014年第6期1309-1316,共8页Acta Pedologica Sinica

基　　金：国家自然科学基金项目(41271244);陕西省社会发展攻关项目(2013K13-01-05);陕西省农业科技攻关项目(2012K02-15)资助

摘　　要：采用不同比例十二烷基二甲基甜菜碱(BS-12)+Tween20复配修饰膨润土,以批处理法研究了不同修饰比例、温度、p H、离子强度下,修饰膨润土对Cd2+吸附的效果,并从吸附等温线、温度效应和热力学角度探讨了吸附机制。结果表明,供试土样对Cd2+的平衡吸附量呈现BS+0.25T>BS+0.5T>BS>BS+1T>BS+1.5T>CK的趋势,复配修饰土样对Cd2+的吸附随Tween20修饰比例的增加而降低。Tween20复配修饰比例小于0.5时有利于复配修饰土对Cd2+的吸附,而大于0.5时复配修饰土对Cd2+的吸附量则降低。修饰膨润土对Cd2+的吸附等温线均符合Langmuir模型。温度升高、p H增加、复配修饰土对Cd2+的吸附量增加、离子强度的增大减弱了土样对Cd2+的吸附。热力学参数结果表明,修饰土样对Cd2+的吸附是熵增控制的自发性过程;各土样对Cd2+吸附均为吸热过程。Pollution of groundwater and soil by heavy metals and organic substances is getting increasingly serious. In the polluted soil or water, the pollutants often exist simultaneously, to remedy the soil or water, the method of fixation through adsorption is one of the most effective ways. Organically-modified soils can effectively adsorb organic compounds. Amphoteric surfactant modified soils can adsorb organic substances and heavy metals at the same time, but their organic pollutants adsorption capacity is not so high as cationic modified soils. In order to enhance their capacity, they are further modified with another type of surfactant modifier. For that end, bentonite was modified with dodecyl dimethyl betaine （BS-12） ＋ Tween20 complex varying in ratio by wet chemical method and effects of the modified bentonites adsorbing Cd2 relative to ratio of the modifier （in terms of total carbon ratio of Tween20/BS-12, set at 0.25, 0.5, 1 and 1.5）, temperature （20，30 and 40℃）, pH （3, 5 and 7）, ionic strength （0.05，0.10 and 0.50 mol L-1） were explored using the batch experiments and control variate method, and mechanism of the adsorption was studied from the aspects of adsorption isotherms （Model fitting, using the CurveExpert 1.4 nonlinear fitting software and the stepwise approximation method for nonlinear fitting）, temperature effects and thermodynamics. Results show that the equilibrium Cd2 adsorption capacity of Tween20 complex modified bentonite varied with modification ratio, displaying an order of BS 0.25T 〉 BS 0.5T 〉 BS 〉 BS 1 T 〉 BS 1.5 T 〉 CK, which means that when the ratio ranged between 0 and 0.5, the capacity rose with the ratio, but when the ratio exceeded 0.5, the capacity decreased with the rising ratio, which demonstrates that the Tween20 modification ratio, less than 0.5, is in favor of Cd2 adsorption on modified bentonite. The adsorption isotherms of Cd2 on modified bentonite can be described with the Langmuir model. Within the experimental range that ensured Cd

关 键 词：膨润土 两性修饰 非离子表面活性剂 Cd2+ 吸附 

分 类 号：X53[环境科学与工程—环境工程]