不同污染负荷土壤中镉和铅的吸附-解吸行为

Sorption-desorption behaviors of Cd^(2+) and Pb^(2+) in different pollution load soils

采用一次平衡法,对3种不同污染负荷土壤Cd2+和Pb2+的吸附-解吸行为进行了比较.结果表明,低污染负荷土壤对Cd2+和Pb2+的吸附能力高于高污染负荷土壤.3种土壤对Cd2+的吸附等温线与Freundlich方程有较好的拟合性,Pb2+的等温吸附过程可用Langmuir方程与Freundlich方程来描述.双常数方程是描述这3种不同污染负荷土壤中Cd2+和Pb2+吸附动力学行为的最优模型,其次为Elovich方程,最差模型是一级动力学方程.Pb2+的解吸滞后现象较Cd2+明显.高污染负荷土壤的吸附态Cd2+、Pb2+解吸率高于低污染负荷土壤,Cd2+、Pb2+解吸量与其初始吸附量之间的关系符合二次幂方程.3种土壤Cd2+、Pb2+的解吸速率随重金属初始浓度的增加而增加,随解吸时间的延长而降低.

With batch method, this paper studied the sorption-desorption behaviors of Cd and Pb in soils with heavy, medium, and slight pollution loads. The results showed that the soil with slight pollution load had a high sorption capacity of Cd^2＋ and Pb^2＋ than the other two. For the three test soils, the isothermal curve of Cd^2＋ sorption fitted Freundlich equation better, while that of Pb^2＋ sorption could be well described with Langmuir equation and Freundlich equation. Two-constant equation was the best model to describe the sorption kinetics of Cd^2＋ and Pb^2＋ , Elovich equation was the second, and the worst was first-order dynamics equation. The desorption lag of Pb^2＋ was more obvious than that of Cd^2＋ , and the desorption rates of adsorbed Cd^2＋ and Pb^2＋ were higher in the soil with heavy pollution load. The relationships between the desorbed and the initial absorbed amounts of Cd^2＋ and Pb^2＋ fitted quadratic equation. In test soils, the desorption rates of Cd^2＋ and Pb^2＋ increased with increasing initial concentrations of Cd^2＋ and Pb^2＋ , but decreased with increasing duration of desorpion.