黏土矿物中重金属离子的吸附规律及竞争吸附

Adsorption and competitive adsorption of heavy metal ion by clay mineral

采用等温吸附法,研究了重金属铜、铅、镉、镍在膨润土中的吸附特征,发现膨润土对铜、铅的吸附明显强于镉、镍,吸附强度大小顺序为Pb2+>Cu2+>Ni2+>Cd2+。Langmuir和Freundlich方程对这4种金属离子等温吸附的拟合均呈极显著关系。Pb2+、Cd2+、Ni2+分别与Cu2+的双组分竞争吸附表明,黏土矿物对4种离子具有"选择性吸附"。在Pb2+、Ni2+、Cd2+的存在条件下,黏土矿物对Cu2+的吸附产生不同程度的下降;100mg/LCu2+对Pb2+的影响不大,但可完全抑制Ni2+、Cd2+的吸附。建立了IAS和LCA模型来预测Pb2+与Cu2+的双组分竞争吸附,并对LCA模型进行修正,提出了更符合实际情况的竞争吸附模型。文章最后用LCA修正模型对Pb2+与Cu2+的双组分竞争吸附进行了模拟。

A batch experiment was conducted to study the adsorption of copper, lead, cadmium and nickel by bentonite in single component and binary systems. The results showed that adsorption capacity of copper and lead are higher than that for cadmium and nickel. The order of adsorption capacity was as follows： Pb^2＋ 〉 Cu^2＋ 〉 Ni^2＋ 〉 Cd^2＋. The single ion equilibrium data were fitted to Langmuir and Freundlich isotherms. The adsorption isotherms in binary-component systems showed that there were competition between copper and lead, copper and cadmium, copper and nickel. Adsorption of copper was depressed by the presence of lead in the adsorption solution, but adsorption of lead was depressed little by the presence of copper. Adsorption of copper was also depressed by the presence of nickel and cadmium, however adsorption of nickel and cadmium were completely depressed by the presence of 100 mg/L Cu^2＋. Equilibrium data for the binary adsorption of copper and lead were analyzed by using Ideal-Adsorption-Solution （IAS） and Langmuir-Competitive- Adsorption models, but these equations weren＇t fitted to data for the mixed solutions. The Modified LCA model fits the binary adsorption equilibrium data satisfactorily and adequately. Finally, binary-component competitive adsorption of copper and lead was simulated by Modified LCA model in computer.