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| Effect of ionic strength on adsorption of As（Ⅲ） and As（Ⅴ） on variable charge soils | |
| 作者姓名： | XU Renkou WANG Yong TIWARI Diwakar WANG Houyan |
| 作者单位： | XU Renkou,WANG Houyan(State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences,Nanjing 210008, China);WANG Yong(State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences,Nanjing 210008, China;Graduate University of Chinese Academy of Sciences, Beijing 100049, China);TIWARI Diwakar(Department of Chemistry, Mizoram University, Tanhril Campus, Aizawl 796009, India) |
| 基金项目： | the Knowledge Innovation Program Foundation of the Chinese Academy of Sciences，国家自然科学基金 |
| 摘 要： | The study was to investigate the adsorption behavior of arsenite (As(Ⅲ)) and arsenate (As(Ⅴ)) on two variable charge soils, i.e., Haplic Acrisol and Rhodic Ferralsol at different ionic strengths and pH with batch methods. Results indicated that the amount of As(Ⅲ) adsorbed by these two soils increased with increasing solution pH, whereas it decreased with increasing ionic strength under the acidic condition. This suggested that As(Ⅲ) was mainly adsorbed on soil positive charge sites through electrostatic attraction under the acidic condition. Moreover, intersects of As(Ⅴ) adsorption-pH curves at different ionic strengths (a characteristic pH) are obtained for both soils. It was noted that above this pH, the adsorption of As(Ⅴ) was increased with increasing ionic strength, whereas below it the reverse trend was true. Precisely the intersect pH was 3.6 for Haplic Acrisol and 4.5 for Rhodic Ferralsol, which was near the values of PZSE (soil point of zero salt effect) of these soils. The effects of ionic strength and pH on arsenate adsorption by these soils were interpreted by the adsorption model. The results of zeta potential suggested that the potential in adsorption plane becomes less negative with increasing ionic strength above soil PZSE and decreases with increasing ionic strength below soil PZSE. These results further supported the hypothesis of the adsorption model that the potential in the adsorption plane changes with ionic strength with an opposite trend to surface charge of the soils. Therefore, the change of the potential in the adsorption plane was mainly responsible for the change of arsenate adsorption induced by ionic strength on variable charge soils. |
| 关 键 词： | 可变电荷土壤 离子强度 吸附 |
| 收稿时间： | 21 August 2008 |
| 修稿时间： | 19 November 2008 |
Effect of ionic strength on adsorption of As(III) and As(V) on variable charge soils |
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| XU Renkou,WANG Yong,TIWARI Diwakar,WANG Houyan.Effect of ionic strength on adsorption of As(III) and As(V) on variable charge soils[J].Journal of Environmental Sciences,2009,21(7):927-932. | |
| Authors: | XU Renkou WANG Yong TIWARI Diwakar and WANG Houyan |
| Institution: | 1. State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences,Nanjing 210008, China 2. State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences,Nanjing 210008, China;Graduate University of Chinese Academy of Sciences, Beijing 100049, China 3. Department of Chemistry, Mizoram University, Tanhril Campus, Aizawl 796009, India |
| Abstract: | The study was to investigate the adsorption behavior of arsenite (As(Ⅲ)) and arsenate (As(Ⅴ)) on two variable charge soils, i.e., Haplic Acrisol and Rhodic Ferralsol at different ionic strengths and pH with batch methods. Results indicated that the amount of As(Ⅲ) adsorbed by these two soils increased with increasing solution pH, whereas it decreased with increasing ionic strength under the acidic condition. This suggested that As(Ⅲ) was mainly adsorbed on soil positive charge sites through electrostatic attraction under the acidic condition. Moreover, intersects of As(Ⅴ) adsorption-pH curves at different ionic strengths (a characteristic pH) are obtained for both soils. It was noted that above this pH, the adsorption of As(Ⅴ) was increased with increasing ionic strength, whereas below it the reverse trend was true. Precisely the intersect pH was 3.6 for Haplic Acrisol and 4.5 for Rhodic Ferralsol, which was near the values of PZSE (soil point of zero salt effect) of these soils. The effects of ionic strength and pH on arsenate adsorption by these soils were interpreted by the adsorption model. The results of zeta potential suggested that the potential in adsorption plane becomes less negative with increasing ionic strength above soil PZSE and decreases with increasing ionic strength below soil PZSE. These results further supported the hypothesis of the adsorption model that the potential in the adsorption plane changes with ionic strength with an opposite trend to surface charge of the soils. Therefore, the change of the potential in the adsorption plane was mainly responsible for the change of arsenate adsorption induced by ionic strength on variable charge soils. |
| Keywords: | arsenic adsorption ionic strength Haplic Acrisol Rhodic Ferralsol zeta potential |
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