Influence of pH and Cations Contained in Rainwater on Leaching of Cd(II) from Artificially Contaminated Montmorillonite
Influence of pH and Cations Contained in Rainwater on Leaching of Cd(II) from Artificially Contaminated Montmorillonite
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DOI：
10.1016/j.jece.2020.104080
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发表时间：
2020-10
影响因子：
7.7
通讯作者：
Tasuma Suzuki;Kisyo Nakase;Tomohiro Tamenishi;Masakazu Niinae
中科院分区：
文献类型：
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作者：
Tasuma Suzuki;Kisyo Nakase;Tomohiro Tamenishi;Masakazu Niinae
研究了雨水中pH值和离子对人工污染蒙脱石中Cd（II）淋溶的影响，旨在加深对土壤Cd（II）淋溶机理的认识。批量镉（II）吸附实验进行前进行浸出实验，并使用表面络合模型与离子交换反应耦合得到的结果进行建模。结果表明，在pH低于6.0时，蒙脱石对Cd（II）的吸附不受pH的影响，但受到NaNO 3的强烈阻碍，表明蒙脱石对Cd（II）的吸附主要是以离子交换的方式进行的。这些结果表明，在典型的雨水pH值范围内（< 6.0），雨水中的背景离子浓度可能是控制污染蒙脱石中Cd（II）浸出水平的重要因素。淋溶实验的结果表明，与预期的那样，在雨水中所含的阳离子的加入显着增强Cd（II）的淋溶与不同的pH值和背景离子的淋溶溶液。例如，对于蒙脱石与Cd（II）的含量为5.36 mmol-Cd kg-1，镉（II）的浸出水平在pH值5.0和6.0之间的范围内增加了两倍，通过添加阳离子包含在雨水中。Na+对Cd（II）淋溶的促进作用较小，K+、NH 4+、Ca 2+、Mg 2+等离子对Cd（II）淋溶的促进作用较大。
The objective of this study was to investigate the influence of pH and ions contained in rainwater on leaching of Cd(II) from artificially-contaminated montmorillonite, with the final objective of deepening the understanding of the leaching mechanism of Cd(II) from soils. Batch Cd(II) sorption experiments were performed before performing leaching experiments, and the obtained results were modeled using a surface complexation model coupled with ion exchange reactions. The results showed that at a pH below 6.0, the sorption of Cd(II) onto montmorillonite was not significantly influenced by pH but was strongly hindered by NaNO3, showing that the dominant Cd(II) sorption mechanism was ion exchange at the permanent charge. These results indicate that for the typical pH range for rainwater (< 6.0), the concentration of background ions in rainwater may be an important factor controlling the leaching level of Cd(II) from contaminated montmorillonite. The result of leaching experiments using leaching solutions with different pH and background ions demonstrated that as expected, the addition of cations contained in rainwater significantly enhanced Cd(II) leaching. For instance, for the montmorillonite with the Cd(II) content of 5.36 mmol-Cd kg-1, the leaching level of Cd(II) at pH range between 5.0 and 6.0 increased twofold by adding cations contained in rainwater. It was also shown that Na+only slightly contributes to enhanced Cd(II) leaching, and other cations including K+, NH4+, Ca2+, and Mg2+are the main contributors to enhanced Cd(II) leaching.