Pedosphere 19(2): 251--257, 2009
ISSN 1002-0160/CN 32-1315/P
©2009 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| A new competitive adsorption isothermal model of heavy metals in soils |
XUE Wen-Bo1, YI Ai-Hua1, ZHANG Zeng-Qiang 1, TANG Ci-Lai1, ZHANG Xing-Chang2 and GAO Jin-Ming1 |
1 College of Sciences, Northwest A&F University, Yangling, Shaanxi 712100 (China). E-mail:xuewenboyah@163.com;
2 Institute of Soil and Water Conservation, Chinese Academy of Sciences, Yangling, Shaanxi 712100 (China) |
| ABSTRACT |
| A new competitive adsorption isothermal model (CAIM) was developed for the coexistent and competitive binding of heavy metals to the soil surface. This model extended the earlier adsorption isothermal models by considering more than one kind of ion adsorption on the soil surface. It was compared with the Langmuir model using different conditions, and it was found that CAIM, which was suitable for competitive ion adsorption at the soil solid-liquid surface, had more advantages than the Langmuir model. The new competitive adsorption isothermal model was used to fit the data of heavy metal (Zn and Cd) competitive adsorption by a yellow soil at two temperatures. The results showed that CAIM was appropriate for the competitive adsorption of heavy metals on the soil surface at different temperatures. The fitted parameters of CAIM had explicit physical meaning. The model allowed for the calculation of the standard molar Gibbs free energy change, the standard molar enthalpy change, and the standard molar entropy change of the competitive adsorption of the heavy metals, Zn and Cd, by the yellow soil at two temperatures using the thermodynamic equilibrium constants. |
| Key Words: combined pollution, competitive adsorption isothermal model, heavy metal, thermodynamic parameters |
| Citation: Xue, W. B., Yi, A. H., Zhang, Z. Q., Tang, C. L., Zhang, X. C. and Gao, J. M. 2009. A new competitive adsorption isothermal model of heavy metals in soils. Pedosphere. 19(2): 251-257. |
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