Study On Adsorption Of Metal Ion By Different Forest Types Soils And Competitive Adsorption Model

Cu²⁺ adsorption of 24 soil samples gathered out of 4 soil layers (0-10,10-20,20-40,40-60 cm) of 6 different types of forests in Anji, Zhejiang were determined to explore relationship of Cu²⁺ adsorption with organic matter content, CEC, pH and particle composition. A batch experiment was conducted to study the adsorption of copper, lead, cadmium and nickel by bentonite in single component and binary systems. The result shows that:(1) In terms of Cu²⁺ adsorption the six types of forests are in the order of broadleaved deciduous forest > shrubbery > tea grove > broadleaved evergreen forest > bamboo grove > pine forest. Cu²⁺ adsorption decreases with the depth of the profile.(2) Organic matter content and CEC are the two major factors affecting soil Cu²⁺ adsorption. Based on the findings, a model is established to illuminate the relationship of Cu²⁺ adsorption with organic matter content and CEC.(3) Adsorption capacity of copper and lead are higher than that for cadmium and nickel by bentonite. The order of adsorption capacity was as follows: Pb²⁺ > Cu²⁺ > Ni²⁺ > Cd²⁺. The single ion equilibrium data were fitted to Langmuir, Freundlich and Temkin isotherms.(4) Maximum adsorption of Cu²⁺ by high energy site is more than by low energy site slightly. The adsorption of Pb²⁺ is mainly determined by high energy site. Maximum adsorption of Cd²⁺ by high energy site is 2.59 mg/g, and 2.45 mg/g by low energy site. It is much more less than maximum adsorption of Pb²⁺ and Cu²⁺. The adsorption of Ni²⁺ is mainly determined by low energy site.(5) 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 Cu²⁺.(6) 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.