Sorption-desorption behaviors of Cd2+ and Pb2+ in different pollution load soils
不同污染负荷土壤中镉和铅的吸附－解吸行为

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 Cd2 and Pb2 than the other two. For the three test soils, the isothermal curve of Cd2 sorption fitted Freundlich equation better, while that of Pb2 sorption could be well described with Langmuir equation and Freundlich equation. Two-constant equation was the best model to describe the sorption kinetics of Cd2 and Pb2 , Elovich equation was the second, and the worst was first-order dynamics equation. The desorption lag of Pb2 was more obvious than that of Cd2 , and the desorption rates of adsorbed Cd2 and Pb2 were higher in the soil with heavy pollution load. The relationships between the desorbed and the initial absorbed amounts of Cd2 and Pb2 fitted quadratic equation. In test soils, the desorption rates of Cd2 and Pb2 increased with increasing initial concentrations of Cd2 and Pb2 , but decreased with increasing duration of desorpion.