College of Civil and Architectural Engineering, Taizhou University, Taizhou, People's Republic of China.
Shanghai Construction Group Co., Ltd., Shanghai, People's Republic of China.
Environ Technol. 2024 Sep;45(21):4169-4180. doi: 10.1080/09593330.2023.2243392. Epub 2023 Aug 4.
Stabilization/solidification is widely used for treatment of arsenic (As)-contaminated soils. The stability of the soil may deteriorate significantly when exposed to acid or alkaline leachate. In this study, semi-dynamic leaching tests under different pH were carried out to investigate the leaching behavior of As from the solidified soils. Spectroscopic and microscopic analyses were performed to reveal the related mechanisms. The results showed that the leaching of As was closely correlated with the pH of the leachate, because the encapsulation effect of the cementitious matrix and the chemical speciation and valence of As were all significantly influenced by pH. In the strongly acidic leachant (pH 3.0), the leached As concentration increased by an order of magnitude, and the effective diffusion coefficient of As reached 3.71 × 10 m/s. This is because that pores and cracks increased owing to the acidic corrosion of CSH, such that the physical encapsulation effect was reduced and the mobility of As increased. The leachability index showed that the solidified soil was unsuitable for 'controlled utilization' under strongly acidic conditions. The leached As concentration was the lowest in the weakly alkaline leachant (pH 9.0) because under weakly alkaline conditions the hydration process of the cement was facilitated, and more CSH gels were attached to the surface of the soil particles, forming a tighter structure for As encapsulation. However, as pH increased from 9.0-11.0 the leached As concentration increased due to an increased content of As(III)-O in the solidified soil.
稳定/固化技术广泛用于处理含砷（As）污染的土壤。当固化土壤暴露于酸性或碱性浸出液时，其稳定性可能会显著恶化。本研究进行了不同 pH 值下的半动态浸出试验，以研究砷从固化土壤中的浸出行为。通过光谱和微观分析揭示了相关机制。结果表明，砷的浸出与浸出液的 pH 值密切相关，因为水泥基质的封装效果以及 As 的化学形态和价态均受 pH 值的显著影响。在强酸性浸出剂（pH 3.0）中，浸出的 As 浓度增加了一个数量级，As 的有效扩散系数达到 3.71×10 m/s。这是因为 CSH 的酸性腐蚀导致孔隙和裂缝增加，从而降低了物理封装效果，增加了 As 的迁移性。浸出率指数表明，在强酸性条件下，固化土壤不适合“控制利用”。在弱碱性浸出剂（pH 9.0）中，浸出的 As 浓度最低，因为在弱碱性条件下，水泥的水化过程得到促进，更多的 CSH 凝胶附着在土壤颗粒表面，形成更紧密的 As 封装结构。然而，当 pH 值从 9.0 增加到 11.0 时，由于固化土壤中 As(III)-O 的含量增加，浸出的 As 浓度增加。
