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| Effects and related mechanisms of magnesium aluminum hydroxides on the improvement of coastal saline-alkali soil |
| Received:December 20, 2017 |
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| KeyWord:saline-alkali soil;magnesium aluminum hydroxide;overlapping of diffuse layers;Zeta potential;desalination |
| Author Name | Affiliation | E-mail | | TIAN Lu | School of Environmental Science and Engineering, Tianjin University, Tianjin 300072, China | | | ZHAO Lin | School of Environmental Science and Engineering, Tianjin University, Tianjin 300072, China | zhaolin@tju.edu.cn | | YANG Yong-kui | School of Environmental Science and Engineering, Tianjin University, Tianjin 300072, China | | | QIAO Zhi | School of Environmental Science and Engineering, Tianjin University, Tianjin 300072, China | |
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| Abstract: |
| This study investigated the overlapping of diffuse layers between magnesium aluminum hydroxide (MAH) and saline-alkali soil colloids in the soil microstructure. The best improvement measure was determined via the salt dissolution experiment, using soils with different ratios of MAH[Mg:Al=3:1 (MAH-1), 2:1 (MAH-2), 1:1 (MAH-3), 1:2 (MAH-4), and 1:3 (MAH-5)]. The results confirmed the existence of the overlapping of diffuse layers between the MAH and saline-alkali soil colloids, even in an alkaline soil environment. The pH and amount of MAH were important factors affecting the overlapping behavior. All five amounts of MAH decreased the pH and salinity of the saline-alkali soil. The improvement effect of acidic MAH on the saline-alkali soil was significantly greater than that of alkaline MAH; MAH-5, which had the highest acidity, had the most significant improvement effects. At the minimum addition of 10 mg·g-1 of MAH-5, 65% of the exchangeable Na was removed in the soils, and the removal efficiency did not significantly increase with increasing amounts of MAH-5. However, the amounts of Ca2+ and N removed significantly increased with increasing amounts of MAH-5 addition. Therefore, the addition of MAH could reduce the adsorption of salt-based ions through the overlapping of diffuse layers, and consequently improve the salination of saline-alkali soil. The most effective measure was determined to be the 1% addition of MAH-5 to soil. |
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