Cd^(2+)、Pb^(2+)在根际和非根际土壤中的吸附-解吸行为

Sorption-Desorption Behavior of Cd^(2+) and Pb^(2+) in Rhizosphere and Bulk Soil

采用1次平衡法对Cd2+、Pb2+在小麦根际和非根际土壤中的吸附-解吸行为进行比较研究.结果表明,根际土对Cd2+和Pb2+的吸附能力高于非根际土,2类土壤对Cd2+的吸附等温线与Freundlich方程有较好的拟合性,Pb2+的等温吸附过程可由Langmuir方程与Freundlich方程来描述.双常数方程是描述根际、非根际土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.Cd2+、Pb2+的解吸存在滞后现象,相比于非根际土,根际土吸附态Cd2+、Pb2+的解吸率更低,Cd2+、Pb2+的解吸量与其初始吸附量之间的关系符合2次幂方程.2类土壤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不断降低.描述根际和非根际土Cd2+、Pb2+的解吸动力学过程的最优模型均为双常数方程,其次为Elovich方程,一级动力学方程拟合效果不佳.

Sorption-desorption behavior of Cd^2＋ and Pb^2＋ in the rhizosphere and bulk soil of wheat was studied by the batch method. The results indicated that the sorption capacity of rhizosphere soil to Cd^2＋ and Pb^2＋ was higher than that of bulk soil. Isothermal curves of Cd^2＋ sorption by rhizosphere and bulk soil fitted Freundlich equation well. Isothermal sorption process of Pb^2＋ could be well described by Langmuir equation and Freundlich equation. Two - constant equation was the best model to describe the sorption kinetics of Cd^2＋ and Pb^2＋ , followed by Elovich equation, and the worst model was first-order dynamics equation. There was sorption-desorption hysteresis of Cd^2＋ and Pb^2＋ . The desorptive rates of Cd^2＋ and Pb^2＋ in rhizosphere soil was lower than that of bulk soil. The relationship between desorptive quantity of Cd^2＋ and Pb^2＋ in two soils and the initial sorptive quantity coincided with quadratic equation. The desorptive rates of Cd^2＋ and Pb^2＋ in two soils increased with the higher initial concentrations of Cd^2＋ and Pb^2＋ in the treatments, and decreased with the increasing desorptive time. Two- constant equation was the optimal model to describe the desorptive kinetics of Cd^2＋ and Pb^2＋ in the two soils, and followed by Elovich equation, while the first-order dynamics equation fitted not well.