蛭石在非缓冲与缓冲体系中的Zn^(2+)、Cd^(2+)吸附行为研究

Adsorption of Zn^(2+) and Cd^(2+) on vermiculite in buffer and non-buffer systems

探讨了蛭石分别在非缓冲体系与缓冲体系中的Zn2+、Cd2+吸附行为,比较了2个体系中Zn2+、Cd2+的平衡吸附量(qe),qe与平衡液相离子浓度(ce)、qe与ce和吸附剂浓度(W0)之比(ce/W0)的对应关系。结果表明,在非缓冲体系与缓冲体系中,在3个W0水平上,Zn2+、Cd2+都具有其独立的qe—ce等温吸附曲线,而qe与ce/W0具有良好的相关性,在3个W0水平上的qe—ce/W0等温吸附曲线基本拟合在一起,即在qe—ce/W0等温吸附曲线中均基本消除了吸附剂浓度效应;加入缓冲溶液的传统方法并不能消除W0对离子吸附效果的影响;缓冲体系中,大量的其他阳离子参与Zn2+、Cd2+的竞争吸附,从而使得Zn2+、Cd2+的qe相对降低;缓冲体系的qe—ce、qe—ce/W0等温吸附曲线与非缓冲体系相比,线性形式更为明显,缓冲体系的qe—ce/W0等温吸附曲线中,qe与ce/W0的对应关系没有非缓冲体系中的好。

Experiments of gn2＋ and Cd2＋ adsorptions by three concentration level of vermiculitein in buffer and non-buffer solutions were conducted to compare the adsorption behavior of Zn2＋ and Cd2＋ in two systems. Two types of adsorption isotherms were established by index of absorption quantity （qo）, equilibrium concentration （ce） and ratio of % to the concentration of adsorbent （W0）. The results showed that the adsorption of Zn2＋ and Cd2＋ at three level of W0 had independent qe--ce adsorption isotherm both in buffer and in non-buffer solutions. The qo was well correlated with cc/Wo, and the qe--ce/Wo adsorption isotherms obtained at three W0 level coincided with each other. The absorption quantity of aim ions was relative low in buffer solutions for the competition of other cations; the qe--ce and qe--ce/Wo adsorption isotherm in buffer solutions presented more obvious liner form than that in non-buffer solutions, while the correspondence of qe and ce/Wo in non-buffer solutions was better than that in buffer solutions. The present findings sug- gest that the method of containing buffer solution to eliminate the adsorbent effect was not advisable.