Minerals to Metals Initiative (MtM), Department of Chemical Engineering, University of Cape Town, Private Bag X3, Rondebosch, 7701 Cape Town, South Africa.
Minerals to Metals Initiative (MtM), Department of Chemical Engineering, University of Cape Town, Private Bag X3, Rondebosch, 7701 Cape Town, South Africa; Centre for Bioprocess Engineering Research, Department of Chemical Engineering, University of Cape Town, Private Bag X3, Rondebosch, 7701 Cape Town, South Africa.
Sci Total Environ. 2022 Nov 10;846:157178. doi: 10.1016/j.scitotenv.2022.157178. Epub 2022 Jul 15.
Understanding the fundamental controls that govern the generation of mine drainage is essential for waste management strategies. Combining the isotopic composition of water (H and O) and dissolved sulfate (S and O) with hydrogeochemical measurements of surface and groundwater, microbial analysis, composition of sediments and precipitates, and geochemical modeling results in this study we discussed the processes that control mine water chemistry and identified the potential source(s) and possible mechanisms governing sulfate formation and transformation around a South African colliery. Compared to various South African water standards, water samples collected from the surroundings of a coal waste disposal facility had elevated Fe (0.9 to 56.9 mg L), Ca (33.0 to 527.0 mg L), Mg (6.2 to 457.0 mg L), Mn (0.1 to 8.6 mg L) and SO (19.7 to 3440.8 mg L) and circumneutral pH. The pH conditions are mainly controlled by the release of H from pyrite oxidation and the subsequent dissolution of carbonates and aluminosilicate minerals. The phases predicted to precipitate by equilibrium calculation were green rusts, ferrihydrite, gypsum, ±epsomite. Low concentrations of deleterious metals in solution are due to their low abundance in the local host rocks, and their attenuation through adsorption onto secondary Fe precipitates and co-precipitation at the elevated pH values. The δS values of sulfate are enriched (-6.5 ‰ to +5.6 ‰) compared to that of pyrite sampled from the mine (mean -22.5 ‰) and overlap with that of the organic sulfur of coal from the region (-2.5 to +4.9 ‰). The presence of both sulfur reducing and oxidizing bacteria were detected in the collected sediment samples. Combined, the data are consistent with the dissolved sulfate in the sampled waters from the colliery being derived primarily from pyrite probably with the subordinate contribution of organic sulfur, followed by its partial removal through precipitation and microbially-induced reduction.
了解控制矿山排水产生的基本控制因素对于废物管理策略至关重要。本研究将水（H 和 O）和溶解硫酸盐（S 和 O）的同位素组成与地表水和地下水的水文地球化学测量、微生物分析、沉积物和沉淀物的组成以及地球化学模型相结合，讨论了控制矿山水化学的过程，并确定了南非煤矿周围控制硫酸盐形成和转化的潜在来源和可能机制。与各种南非水标准相比，从煤废弃物处置设施周围采集的水样中 Fe（0.9 至 56.9mg/L）、Ca（33.0 至 527.0mg/L）、Mg（6.2 至 457.0mg/L）、Mn（0.1 至 8.6mg/L）和 SO（19.7 至 3440.8mg/L）含量较高，且 pH 值接近中性。pH 值条件主要受黄铁矿氧化释放 H 和随后碳酸盐和铝硅酸盐矿物溶解的控制。平衡计算预测的沉淀相为绿锈、水铁矿、石膏、±泻盐。溶液中有害金属浓度较低，是由于它们在当地基岩中的丰度较低，以及在较高 pH 值下通过吸附到次生铁沉淀物和共沉淀而衰减。硫酸盐的 δS 值富集（-6.5‰至+5.6‰），与从矿山采集的黄铁矿的 δS 值（平均-22.5‰）相比，与该地区煤的有机硫的 δS 值重叠（-2.5 至+4.9‰）。在采集的沉积物样品中检测到同时存在硫还原菌和硫氧化菌。综合数据表明，从煤矿采集的水样中溶解的硫酸盐主要来源于黄铁矿，可能有少量有机硫的贡献，随后通过沉淀和微生物诱导还原部分去除。
