School of Mechanics and Engineering Science, Shanghai University, Shanghai, 200444, PR China.
Shandong Electric Power Engineering Consulting Institute Co., Ltd., Jinan, 250013, PR China.
Chemosphere. 2022 Nov;306:135598. doi: 10.1016/j.chemosphere.2022.135598. Epub 2022 Jul 6.
The high mobility of As(III) makes it difficult to remediate heavily As(III)-contaminated soil. A novel remediation technique that combines pre-oxidation and stabilization/solidification (PO + S/S) is proposed in this study to remediate heavily As(III)-contaminated soil. After oxidizing As(III) in the contaminated soil using Fenton's reagent, FeCl·6HO was used as a chemical stabilizing agent to reduce the toxicity and mobility of As. Finally, Portland cement (PC) was used for solidification. The effects and mechanisms of the proposed technique were studied using unconfined compressive strength tests, leaching tests, sequential extraction procedure (SEP), and a series of spectroscopic/microscopic investigations. The experimental results showed that the addition of FeCl·6HO increased the strength of the curing body because the hydration degree of PC and pore structure were improved. Portland cement can increase the pH of the curing body. At a 1:1 Fe to As molar ratio and a 15 wt% PC dosage, the leached As concentration decreased to 3.25 mg L, and the remediation efficiency reached 99.54%. The SEP results showed that the PO + S/S treatment converted As into more stable phases and effectively reduced the potential mobile phase risk. The majority of As was bound to hydrated iron oxides; however, the increased pH affected the Fe-As interactions and prompted the release of As from the surface of the hydrated iron oxides. Spectroscopic/microscopic investigations indicated that the PO + S/S treatment converted As(III) to less toxic and less mobile As(V) and then immobilized by the encapsulation of calcium silicate hydrate and ion exchange of ettringite. This study provides a scientific basis and theoretical support for the effective remediation of heavily As(III)-contaminated soil.
砷（III）的高迁移性使其难以修复高砷（III）污染的土壤。本研究提出了一种将预氧化和稳定/固化（PO + S/S）相结合的新型修复技术，用于修复高砷（III）污染的土壤。在用芬顿试剂氧化污染土壤中的砷（III）后，六水合氯化铁（FeCl·6HO）被用作化学稳定剂，以降低砷的毒性和迁移性。最后，使用波特兰水泥（PC）进行固化。通过无侧限抗压强度试验、浸出试验、顺序提取程序（SEP）和一系列光谱/显微镜研究，研究了所提出技术的效果和机制。实验结果表明，添加六水合氯化铁（FeCl·6HO）提高了固化体的强度，因为 PC 的水化程度和孔结构得到了改善。波特兰水泥可以提高固化体的 pH 值。在 1:1 的 Fe 与 As 摩尔比和 15 wt%的 PC 用量下，浸出的 As 浓度降低至 3.25 mg/L，修复效率达到 99.54%。SEP 结果表明，PO + S/S 处理将 As 转化为更稳定的相，有效降低了潜在的可移动相风险。大部分 As 与水合氧化铁结合，但 pH 值的升高影响了 Fe-As 相互作用，并促使 As 从水合氧化铁的表面释放出来。光谱/显微镜研究表明，PO + S/S 处理将 As（III）转化为毒性较小、迁移性较小的 As（V），然后通过硅酸钙水合物的包裹和钙矾石的离子交换将其固定。本研究为有效修复高砷（III）污染土壤提供了科学依据和理论支持。
