ABSTRACT

Arsenic (As) and cadmium (Cd) co-contamination in the soil is a serious global health concern. Three iron-modified fly ash (FA) composites were synthesised, including FA-supported nanoscale zero-valent iron (FA-nZVI), FA-supported FeCl₃ (FA-FeCl₃) and FA-supported Fe-oxyhydroxide sulphate (FA-FeOS) for remediation of As and Cd co-contaminated soil. Soil incubation experiments were conducted to evaluate the effects of iron-modified FA on the soil pH, availability and geochemical fractions of As and Cd. The results showed that FA and FA-nZVI significantly (P < 0.05) increased the soil pH, but FA-FeCl₃ and FA-FeOS decreased the soil pH in general. FA, FA-nZVI, FA-FeCl₃ and FA-FeOS decreased the concentration of available As by 15.13∼21.22%, 46.20∼46.66%, 30.02∼38.09% and 12.05∼30.50%, respectively. However, only FA and FA-nZVI decreased the concentration of available Cd by 4.85∼26.09% and 37.74∼52.18%, respectively. The results showed that FA-nZVI was the most effective amendment for simultaneous immobilisation of As and Cd. Besides, FA-nZVI stimulated the transformation of As and Cd from reactive states to less reachable states to decrease the toxicity of As and Cd in soil. In conclusion, FA-nZVI is a potential amendment for soil remediation in As and Cd co-contaminated soil.

摘要

土壤中的砷 (As) 和镉 (Cd) 共同污染是一个严重的全球健康问题。合成了三种铁改性粉煤灰（FA）复合材料，包括FA负载的纳米级零价铁（FA-nZVI）、FA负载的FeCl ₃（FA-FeCl ₃）和FA负载的羟基氧化硫酸铁（FA- FeOS) 用于修复 As 和 Cd 共污染土壤。进行土壤孵化实验以评估铁改性 FA 对土壤 pH 值、可用性和 As 和 Cd 的地球化学组分的影响。结果表明，FA和FA-nZVI显着提高了土壤pH值（P  < 0.05），而FA-FeCl ₃和FA-FeOS总体上降低了土壤pH值。FA、FA-nZVI、FA-FeCl ₃FA-FeOS 使有效 As 浓度分别降低了 15.13～21.22%、46.20～46.66%、30.02～38.09% 和 12.05～30.50%。然而，只有 FA 和 FA-nZVI 将有效 Cd 的浓度分别降低了 4.85~26.09% 和 37.74~52.18%。结果表明，FA-nZVI 是同时固定 As 和 Cd 最有效的改良剂。此外，FA-nZVI 可刺激 As 和 Cd 从反应态转变为不易达到的态，从而降低土壤中 As 和 Cd 的毒性。总之，FA-nZVI 是一种在 As 和 Cd 共污染土壤中进行土壤修复的潜在改良剂。