Kinetics comparison on simultaneous and sequential competitive adsorption of heavy metals in red soils

WANG Yan(王艳)^{1, 2}, LI Zhong-wu(李忠武)^{1, 2}, HUANG Bin(黄斌)^{1, 2}, JIANG Wei-guo(蒋卫国)³, GUO Liang(郭亮)^{1, 2}, HUANG Jin-quan(黄金权)^{1, 2}, ZENG Guang-ming(曾光明)^{1, 2}

(1. College of Environmental Science and Engineering, Hunan University, Changsha 410082, China;
2. Key Laboratory of Environmental Biology and Pollution Control of Ministry of Education
(Hunan University), Changsha 410082, China;
3. State Key Laboratory of Earth Surface Processes and Resource Ecology (Beijing Normal University),
Beijing 100875, China)

Abstract:To compare the adsorption kinetics of Cu, Zn and Cd introduced into red soils simultaneously and sequentially as well as their distribution coefficients, the ability of red soils to retain heavy metals was evaluated by performing batch experiments. The results indicate that Cu is preferentially adsorbed by red soils no matter in simultaneous or in sequential situation. The adsorption amount of Cd is the minimum in simultaneous competitive adsorption experiment. As heavy metals are added into red soils sequentially, the heavy metal adsorptions are relatively hard to reach equilibrium in 2 h. Red soils retain more Cd than Zn, which is opposite to the result in simultaneous adsorption. The addition sequences of heavy metals affect their adsorbed amounts in red soils to a certain extent. The joint distribution coefficients of metals in simultaneous adsorption are slightly higher than those in sequential adsorption.

Key words:kinetics; simultaneous system; sequential system; competitive adsorption; red soils