Abstract：
The environmental threat posed by stibnite is an important geoenvironmental issue of current concern. To better understand stibnite oxidation pathways, aerobic abiotic batch experiments were conducted in aqueous solution with varying δ18OH2O value at initial neutral pH for different lengths of time (15-300 days). The sulfate oxygen and sulfur isotope compositions as well as concentrations of sulfur and antimony species were determined. The sulfur isotope fractionation factor (Δ34SSO4-stibnite) values decreased from 0.8‰ to -2.1‰ during the first 90 days, and increased to 2.6‰ at the 180 days, indicating the dominated intermediate sulfur species such as S2O32-, S0, and H2S (g) involved in Sb2S3 oxidation processes. The incorporation of O into sulfate derived from O2 (∼100%) indicated that the dissociated O2 was only directly adsorbed on the stibnite-S sites in the initial stage (0-90 days). The proportion of O incorporation into sulfate from water (27%-52%) increased in the late stage (90-300 days), which suggested the oxidation mechanism changed to hydroxyl attack on stibnite-S sites promoted by nearby adsorbed O2 on stibnite-Sb sites. The exchange of oxygen between sulfite and water may also contributed to the increase of water derived O into SO42-. The new insight of stibnite oxidation pathway contributes to the understanding of sulfide oxidation mechanism and helps to interpret field data.
摘要：
辉石造成的环境威胁是当前关注的重要地质环境问题。为了更好地了解辉钼矿氧化途径，需氧非生物分批实验在初始中性pH下在不同的δ18OH2O值的水溶液中进行不同的时间长度（15-300天）。确定了硫酸盐氧和硫同位素组成以及硫和锑物种的浓度。在最初的90天内，硫同位素分馏因子（Δ34SSO4-stibnite）值从0.8‰下降到-2.1‰，在180天增加到2.6‰，表示主要的中间硫物种，如S2O32-，S0，与H2S(g)介入Sb2S3的氧化进程。将O掺入衍生自O2的硫酸盐中（〜100％）表明，解离的O2仅在初始阶段（0-90天）直接吸附在stibnite-S位点上。在后期（90-300天），O掺入水中硫酸盐的比例（27％-52％）增加，这表明氧化机理转变为羟基攻击辉石-S位点，这是由辉石-Sb位点附近吸附的O2促进的。亚硫酸盐和水之间的氧交换也可能有助于水衍生的O增加成SO42-。辉锡矿氧化途径的新见解有助于了解硫化物氧化机理，并有助于解释现场数据。
