胶体存在时不同质地土壤对锌镉的吸附试验研究

以重金属离子Zn和Cd及胶体为对象,通过等温静态批量平衡吸附试验,分析了3种不同质地土壤对Zn、Cd单一吸附和等量竞争吸附特征,胶体对土壤吸附Zn、Cd的影响,并用Langmuir和Freundlich方程对试验结果进行了拟合。结果表明,随着平衡液中Zn2+、Cd2+浓度的增加,土壤对Zn、Cd的吸附量逐渐增大;3种质地土壤对Zn、Cd吸附量顺序为砂壤>粉壤>壤砂土;Zn2+、Cd2+共存时,土壤对这两种离子的吸附量比单一离子存在的情况下明显下降;胶体存在时抑制了土壤对Zn的吸附,促进了土壤对Cd的吸附;就本试验来说,Freundlich方程拟合效果优于Langmuir方程。

Study on Zn and Cd colloid-affected adsorption in three different soils

Heavy metal ions of zinc, cadmium and colloid were used through the batch experiment to study the single and competitive adsorption behavior of zinc and cadmium in three soils different in texture and the effects of the colloid on the adsorption amounts. The Langmuir equation and Freundlich equation were used to fit the experiment data. The results indicated that the adsorption amounts of zinc and cadmium in soils increased with the increasing equilibrium concentration; the sequence of the adsorption amounts of three soils was sandy loam > silty loam > loamy sand; the adsorption amounts of the two ions in the competitive experiment were less than those in single system; the colloid increased the adsorption amounts of zinc but decreased the adsorption amounts of cadmium. In this paper, Freundlich equation was more accurately than the Langmuir equation in describing adsorption behavior of two heavy metals.