State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, PR China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai, 200092, PR China; International Joint Research Center for Sustainable Urban Water System, Tongji University, Shanghai, 200092, PR China.
State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, PR China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai, 200092, PR China.
Chemosphere. 2019 Aug;228:370-376. doi: 10.1016/j.chemosphere.2019.04.132. Epub 2019 Apr 18.
Batch tests were conducted in this study to evaluate the influence of sulfidation on the remediation of Cr(VI) in soil by zero-valent iron (ZVI). It was demonstrated that sulfidated ZVI synthesized by ball-milling with elemental sulfur (S-ZVI) could reduce and immobilize Cr(VI) in soil more rapidly and efficiently than unamended ZVI (ZVI). Specifically, with the optimal S/Fe molar ratio of 0.05 and ZVI dosage of 5 wt%, S-ZVI could completely sequestrate water soluble Cr(VI) (as high as 17.5 mg/L) within 3 h, while negligible Cr(VI) was reduced by ZVI over a 3-day incubation period under identical conditions. Furthermore, sequential extraction analysis revealed that S-ZVI treatment also promoted the conversion of exchangeable Cr to more stable forms (i.e., mainly as FeMn oxides bound fraction). XPS analysis showed that reduction was the main Cr(VI) remediation mechanism by ZVI, and alkaline extraction experiments further demonstrated Cr(VI) concentration in soil could be decreased from 153.6 mg/kg to 23.4 and 131.6 mg/kg by S-ZVI and ZVI, respectively. A magnetic separation process was introduced in this study to physically remove the residual ZVI particles and attached iron (hydr)oxides so as to minimize the re-release risk of immobilized Cr. Results revealed that, 71-89% of the added Fe and 9.5-33.6% of Cr could be retrieved from S-ZVI-treated soil. These findings highlighted the potential of S-ZVI as a promising amendment for immobilizing Cr(VI) in soil and the potential of magnetic separation as an alternative option for preventing the re-mobilization of sequestered Cr.
本研究进行了批实验，以评估硫化对零价铁（ZVI）修复土壤中六价铬（Cr(VI)）的影响。研究表明，通过元素硫（S-ZVI）球磨合成的硫化零价铁（S-ZVI）比未经修饰的 ZVI（ZVI）更能快速、有效地还原和固定土壤中的 Cr(VI)。具体而言，在最佳 S/Fe 摩尔比为 0.05 和 ZVI 剂量为 5wt%的条件下，S-ZVI 可在 3 小时内完全固定水溶态 Cr(VI)（高达 17.5mg/L），而在相同条件下，ZVI 在 3 天的孵育期内几乎没有还原 Cr(VI)。此外，连续提取分析表明，S-ZVI 处理还促进了可交换态 Cr 向更稳定形态的转化（即主要为 FeMn 氧化物结合态）。XPS 分析表明，还原是 ZVI 修复 Cr(VI)的主要机制，碱性提取实验进一步表明，通过 S-ZVI 和 ZVI 处理，土壤中 Cr(VI)浓度可分别从 153.6mg/kg降低至 23.4mg/kg 和 131.6mg/kg。本研究引入了磁分离工艺，以物理去除残留的 ZVI 颗粒和附着的铁（氢）氧化物，从而最大程度地降低固定化 Cr 的再释放风险。结果表明，S-ZVI 处理土壤中添加的 Fe 有 71-89%和 Cr 有 9.5-33.6%可以回收。这些发现突出了 S-ZVI 作为一种有前途的土壤中 Cr(VI)固定剂的潜力，以及磁分离作为防止固定化 Cr 再迁移的替代选择的潜力。
