Pedosphere 17(1): 90--96, 2007
ISSN 1002-0160/CN 32-1315/P
©2007 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Hydrolysis of aluminum ions in kaolinite and oxisol suspensions as influenced by organic anions |
XU Ren-Kou1 , XIAO Shuang-Cheng1, LI Jiu-Yu1,2, D. TIWARI3 and JI Guo-Liang1 |
1 State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (Chian), Email: rkxu@issas.ac.cn;
2 Graduate University of Chinese Academy of Sciences, Beijing 100039 (China);
3 Department of Chemistry, National Institute of Technology, Jamshedpur-831014 (India) |
| ABSTRACT |
| To evaluate the role of kaolinite and variable charge soils on the hydrolytic reaction of Al, the hydrolysis of Al ions in suspensions of a kaolinite and an Oxisol influenced by organic anions was investigated using changes of pH, Al adsorption, and desorption of pre-adsorbed Al. Kaolinite and the Oxisol promoted the hydrolytic reaction of Al above a certain initial Al concentration (0.1 mmol L-1 for kaolinite and 0.3 mmol L-1 for the Oxisol). The Al hydrolysis accelerated by kaolinite and the Oxisol increased with an increase in initial concentration of Al and was observed in the range of pH from 3.7 to 4.7 for kaolinite and 3.9 to 4.9 for the Oxisol. The acceleration of Al hydrolysis also increased with the increase of solution pH, reached a maximum value at pH 4.5, and then decreased sharply. Al hydrolysis was promoted mainly through selective adsorption for hydroxy-Al. Soil free iron oxides compensated a portion of the soil negative charge or masked some soil surface negative sites leading to a decrease in Al adsorption, which retarded acceleration to some extent. For the Oxisol organic anions increased the proportion of adsorbed Al3+ in total adsorbed Al with the increase in soil negative surface charge and eliminated or reduced the acceleration of Al hydrolysis. Different organic anions inhibited the hydrolysis of Al in the order: citrate > oxalate > acetate (under initial pH of 4.5). The formation of Al-organic complexes in solution also inhibited the hydrolysis of Al. |
| Key Words: aluminum hydrolysis, kaolinite, organic anion, Oxisol |
| Citation: Xu, R. K., Xiao, S. C., Li, J. Y., Tiwari, D. and Ji, G. L. 2007. Hydrolysis of aluminum ions in kaolinite and oxisol suspensions as influenced by organic anions. Pedosphere. 17(1): 90-96. |
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