污灌土壤对铅的吸附和解吸特性

Lead(Ⅱ) Adsorption and Desorption onto the Sewage Irrigation Soil

为了解污灌土壤对铅的吸附-解吸机制,进行不同条件下的吸附-解吸试验。结果表明:污灌土壤对铅的吸附量随铅初始浓度的增大,呈现先强烈吸附再缓和的过程。Langmuir模式对污灌土壤等温吸附铅的拟合效果最好,其饱和吸附量为7.84mg/g。亚砷酸盐的存在会阻碍污灌土壤对Pb2+的吸附,亚砷酸盐加入前后污灌土壤对铅的吸附率从99.9%～100%下降到97.8%～99.0%。加亚砷酸盐条件下污灌土壤对铅的等温吸附模式以Freundlich模式的拟合效果最好。污灌土壤对吸附态铅的解吸量随解吸振荡时间的延长而不断增加,且解吸率随时间增加总体趋于降低。Elovich方程和幂函数方程均能很好地拟合污灌土壤对铅的解吸动力学过程,尤其是Elovich方程的拟合效果最为显著。

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.