文献类型： 外文期刊

作者： Zhao, XiuLan ¹ ; Jiang, Tao ¹ ; Du, Bin ¹ ;

作者机构： 1.Southwest Univ, Coll Resources & Environm, Key Lab Ecoenvironm Three Gorges Reservoir Reg, Minist Educ, Chongqing 400715, Peoples R China; Chongqing Key Lab Agr Resources & Environm, Chongqing 400716, Peoples R China

关键词： Cadmium;Purple paddy soil;Adsorption-desorption;Thermodynamic;Organic matter;Calcium carbonate

期刊名称：CHEMOSPHERE （ 影响因子：8.1； 五年影响因子：7.7 ）

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收录情况： SCI

摘要： Batch experiments and sequential extraction analysis were employed to investigate the effects of soil organic matter and CaCO_3 on the adsorption and desorption of cadmium (Cd~(2+)) onto and from two purple paddy soils, an acidic purple paddy soil (APPS) and a calcareous purple paddy soil (CPPS). The Cd~(2+) adsorption isotherms on both soils could be well-described by the Langmuir and Freundlich equations. CPPS had a higher capacity and a stronger affinity for Cd~(2+) adsorption compared with APPS. The adsorption process of Cd~(2+) on APPS was dominated by electrostatic attractions, whereas the adsorption mechanism varied depending on the Cd~(2+) concentrations in equilibrium solutions on CPPS. At low equilibrium concentrations, the adsorption process was primarily specific adsorption, but nonspecific adsorption dominated at high equilibrium concentrations. Removal of organic matter decreased the amount of Cd~(2+) adsorption on both of the soils, slightly affected the Cd~(2+) desorption rate and exchangeable Cd (EXC-Cd) in APPS and increased the desorption rate and EXC-Cd in CPPS, suggesting that the effect of organic matter on Cd~(2+) adsorption-desorption depends on the soils. CPPS and APPS containing CaCO_3 exhibited higher adsorption amounts but lower desorption rates and lower proportions of EXC-Cd than those of their corresponding soils without CaCO_3, demonstrating that CaCO_3 played an important role in Cd~(2+) specific adsorption on soil. The changes in the thermodynamic parameters, including free energy (△G~0), enthalpy (△H~0) and entropy (△S~0), as evaluated by the Van't Hoff equations, indicated that the adsorption was a spontaneous and endothermic process with the primary interaction forces of dipole interactions and hydrogen bonds on APPS, whereas both physical and chemical interactions dominated the adsorption on CPPS.