Abstract:

Batch experiments were undertaken to study the adsorption and desorption mechanisms of lead (Pb, Ⅱ) on the sewage irrigation soil. The results revealed that the adsorption of Pb (Ⅱ) onto the sewage irrigation soil rapidly increased with the increasing initial concentration of Pb in the beginning, and then increased slowly. The sorption isotherm of Pb (Ⅱ) onto the sewage irrigation soil fitted best to Langmuir model, illustrating that the maximum sorption capacity of Pb (Ⅱ) on the soil was 7.84 mg/g. The adsorption of Pb (Ⅱ) onto the sewage irrigation soil decreased in the presence of arsenite, and the adsorption ratio of Pb (Ⅱ) is from99.9%-100% to 97.8%-99.0%.  The adsorption isotherm of Pb (Ⅱ) onto the soil in the presence of arsenite fitted well to Freundlich model. The desorption of Pb (Ⅱ) onto the sewage irrigation soil increased with the desorption time, and the desorption rate of Pb(Ⅱ) onto the soil decreased with the desorption time. The kinetics of desorption of Pb²⁺ onto the sewage irrigation soil are well described by Elovich and power function equations, especially for Elovich equation.

Key words: sewage irrigation soil, lead, adsorption, desorption, arsenite