School of Minerals Processing and Bioengineering, Central South University, Changsha 410083, China.
School of Minerals Processing and Bioengineering, Central South University, Changsha 410083, China.
Water Res. 2022 Sep 1;223:118957. doi: 10.1016/j.watres.2022.118957. Epub 2022 Aug 10.
Mining activities expose sulfidic minerals including arsenopyrite (FeAsS) to acid mine drainage (AMD). The subsequent release of toxic arsenic (As) can have great negative implications for the environment and human health. This study investigated the evolution of secondary products and As speciation transformations during arsenopyrite bio-oxidation in AMD collected from a polymetallic mine. Immobilization of the As solubilized via arsenopyrite bio-oxidation using red mud (RM) was also studied. The results show that the high ionic strength (concentrations of dissolved Fe, SO, and Ca reached values up to 0.75, 3.38, and 0.35 g/L, respectively) and redox potential (up to +621 mV) of AMD (caused primarily by Fe) enhanced the dissolution of arsenopyrite. A high [Fe]/[As] ratio in the AMD favored the precipitation of tooeleite during arsenopyrite bio-oxidation, and the formation of other poorly crystalline products such as schwertmannite and amorphous ferric arsenate also contributed to As immobilization. Bacterial cells served as important nucleation sites for the precipitation of mineral phases. Arsenopyrite completely dissolved after 12 days of bio-oxidation in AMD and the [As] (mainly present as As(III)) reached 1.92 g/L, while a greater [As] was observed in a basal salts medium (BSM) assay (reaching 3.02 g/L). An RM addition significantly promoted As(III) immobilization, with final [As(III)] decreasing to 0.16 and 1.43 g/L in AMD and BSM assays respectively. No oxidation of As(III) was detected during the immobilization process. These findings can help predict As release from arsenopyrite on contact with AMD and, on a broader scale, assist in designing remediation and treatment strategies to mitigate As contamination in mining.
采矿活动将含硫化物的矿物（包括毒砂，FeAsS）暴露于酸性矿山排水（AMD）中。随后有毒砷（As）的释放会对环境和人类健康产生巨大的负面影响。本研究调查了从多金属矿收集的 AMD 中砷的生物氧化过程中次生产物的演化和砷形态的转化。还研究了利用赤泥（RM）固定通过砷的生物氧化溶解的砷。结果表明，AMD 中的高离子强度（溶解的 Fe、SO 和 Ca 的浓度分别高达 0.75、3.38 和 0.35 g/L）和氧化还原电位（高达+621 mV）（主要由 Fe 引起）增强了砷的溶解。AMD 中高的 [Fe]/[As] 比值有利于在砷的生物氧化过程中形成白铁矿，而其他结晶不良的产物如纤铁矿和无定形铁砷酸盐的形成也有助于砷的固定。细菌细胞是矿物相沉淀的重要成核点。砷在 AMD 中的生物氧化 12 天后完全溶解，[As]（主要以 As(III)的形式存在）达到 1.92 g/L，而在基础盐培养基（BSM）试验中观察到更高的[As]（达到 3.02 g/L）。RM 的添加显著促进了 As(III)的固定，最终在 AMD 和 BSM 试验中[As(III)]分别降低到 0.16 和 1.43 g/L。在固定化过程中未检测到 As(III)的氧化。这些发现有助于预测接触 AMD 后砷从毒砂中的释放，并在更广泛的范围内协助设计修复和处理策略以减轻采矿中的砷污染。
