Department of Civil Engineering, Shanghai University, 200444 Shanghai, China.
Department of Civil Engineering, Shanghai University, 200444 Shanghai, China.
Sci Total Environ. 2020 Sep 1;733:139410. doi: 10.1016/j.scitotenv.2020.139410. Epub 2020 May 13.
Cement-based solidification/stabilization (S/S) technology is often used to remediate chromium (Cr) contaminated soils. The valence state and mobility of Cr in soils are closely related with redox potential (E). However, Cr mobilization from the solidified soils influenced by E has received little attention. In this study, semi-dynamic leaching tests and the toxicity characteristic leaching procedure (TCLP) were performed on a S/S treated Cr contaminated soil under various E conditions. The effective diffusion coefficient and leachability index were obtained from the leaching data to investigate the leaching behavior of Cr from the S/S treated soil. Speciation of Cr remained in the sample after the leaching process was obtained through the sequential extraction procedures. The results show that an increase in E increases the effective diffusion coefficient of Cr and, therefore, the amount of Cr leached. This result is attributed to immobile Cr(III) being oxidized to highly mobile Cr(VI). The leachability index results indicate that the cement solidification of Cr contaminated soil may not be appropriate under oxidizing conditions. For the TCLP and sequential extraction procedures, the leached amount of Cr exhibits a strong dependence on E. As E increases, the content of Cr remaining in the soil in unstable phases reduced, and more Cr was released to leachant.
基于水泥的固化/稳定化（S/S）技术常用于修复铬（Cr）污染土壤。土壤中 Cr 的价态和迁移性与氧化还原电位（E）密切相关。然而，受 E 影响的固化土壤中 Cr 的迁移问题尚未得到充分关注。在本研究中，在不同 E 条件下，对经 S/S 处理的 Cr 污染土壤进行了半动态浸出试验和毒性特征浸出程序（TCLP）。从浸出数据中获得有效扩散系数和浸出指数，以研究 Cr 从 S/S 处理土壤中的浸出行为。通过连续提取程序获得浸出过程后样品中残留的 Cr 形态。结果表明，E 的增加会增加 Cr 的有效扩散系数，从而增加 Cr 的浸出量。这一结果归因于不移动的 Cr(III)被氧化为高度移动的 Cr(VI)。浸出指数结果表明，在氧化条件下，Cr 污染土壤的水泥固化可能不合适。对于 TCLP 和连续提取程序，Cr 的浸出量与 E 有很强的依赖性。随着 E 的增加，土壤中不稳定相中的 Cr 残留量减少，更多的 Cr 被释放到浸出剂中。
