Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming, 650093, China.
Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming, 650093, China.
Environ Res. 2023 Jul 15;229:115751. doi: 10.1016/j.envres.2023.115751. Epub 2023 Mar 25.
Mining and smelting are the main sources of soil heavy metal pollution. Leaching and release of heavy metals in soils has been extensively studied. However, there are few researches on the release behavior of heavy metals from the Angle of mineralogy of smelting slag. This study focuses on the pollution of arsenic and chromium by traditional pyrometallurgical lead-zinc smelting slag in southwest China. Based on the mineralogy of smelting slag, the release behavior of heavy metals in smelting slag was studied. As and Cr deposit minerals were identified by MLA analysis, and the weathering degree and bioavailability of As and Cr deposit minerals were analyzed. The results showed that the weathering degree of slag was positively correlated with the bioavailability of heavy metals. The leaching experiment results showed that the higher pH was beneficial to the release of As and Cr. It was found that the chemical forms of As and Cr changed from relatively stable forms to easily released forms (As5+ to As3+ and Cr3+ to Cr6+) by characterizing the metallurgical slag during leaching. In the transformation process, the S in the pyrite as the enclosing layer is eventually oxidized to SO42-, which will accelerate the dissolution of the enclosing mineral. SO42- will occupy the adsorption site of As on the mineral surface, thus reducing the adsorption amount of As on the mineral surface. Fe is finally oxidized to Fe2O3, and the increase of Fe2O3 content in the waste residue will produce strong adsorption effect on Cr6+ and slow down the release of Cr6+. The results show that the release of As and Cr is controlled by the pyrite coating.
采矿和冶炼是土壤重金属污染的主要来源。土壤中重金属的浸出和释放已经得到了广泛的研究。然而，关于从冶炼渣的矿物学角度研究重金属释放行为的研究较少。本研究以中国西南地区传统火法炼铅锌渣中砷和铬的污染为研究对象。基于冶金渣的矿物学，研究了冶金渣中重金属的释放行为。通过 MLA 分析确定了 As 和 Cr 赋存矿物，分析了 As 和 Cr 赋存矿物的风化程度和生物有效性。结果表明，渣的风化程度与重金属的生物有效性呈正相关。浸出实验结果表明，较高的 pH 值有利于 As 和 Cr 的释放。通过对浸出过程中的冶金渣进行表征，发现 As 和 Cr 的化学形态从相对稳定的形态转变为易释放的形态（As5+转变为 As3+，Cr3+转变为 Cr6+）。在转化过程中，黄铁矿中的 S 作为包裹层最终被氧化为 SO42-，这将加速包裹矿物的溶解。SO42-将占据矿物表面上 As 的吸附位，从而减少 As 在矿物表面上的吸附量。Fe 最终被氧化为 Fe2O3，废渣中 Fe2O3 含量的增加会对 Cr6+产生强烈的吸附作用，从而减缓 Cr6+的释放。结果表明，As 和 Cr 的释放受黄铁矿包裹层控制。
