Southern Cross GeoScience, Southern Cross University , Lismore, NSW 2480, Australia.
Environ Sci Technol. 2017 Apr 18;51(8):4259-4268. doi: 10.1021/acs.est.6b05335. Epub 2017 Apr 5.
Jarosite can be an important scavenger for arsenic (As) and antimony (Sb) in acid mine drainage (AMD) and acid sulfate soil (ASS) environments. When subjected to reducing conditions, jarosite may undergo reductive dissolution, thereby releasing As, Sb, and Fe coincident with a rise in pH. These conditions can also trigger the Fe-induced transformation of jarosite to more stable Fe(III) minerals, such as goethite. However, the consequences of this transformation process for As and Sb are yet to be methodically examined. We explore the effects of abiotic Fe-induced transformation of jarosite on the mobility, speciation, and partitioning of associated As(V) and Sb(V) under anoxic conditions at pH 7. High concentrations of Fe (10 and 20 mM) rapidly (<10 min) transformed jarosite to a green rust intermediary, prior to the subsequent precipitation of goethite within 24 h. In contrast, lower concentrations of Fe (1 and 5 mM) led to the formation of lepidocrocite. As K-edge XANES spectroscopy revealed some reduction of As(V) to As(III) at higher concentrations of Fe, while Sb L-edge XANES spectroscopy indicated no reduction of Sb(V). The transformation processes enhanced Sb mobilization into the aqueous phase, while As was instead repartitioned to a surface-bound exchangeable phase. The results imply that Fe-induced transformation of As/Sb-jarosite can increase Sb mobility and exert major influences on As partitioning and speciation.
黄钾铁矾可以作为酸性矿山排水（AMD）和酸性硫酸盐土壤（ASS）环境中砷（As）和锑（Sb）的重要清除剂。当处于还原条件下时，黄钾铁矾可能会经历还原溶解，从而释放出 As、Sb 和 Fe，同时 pH 值上升。这些条件还可能引发黄钾铁矾向更稳定的 Fe(III)矿物（如针铁矿）的 Fe 诱导转化。然而，这种转化过程对 As 和 Sb 的后果尚未得到系统的研究。我们探讨了在无氧条件下，pH 值为 7 时，生物诱导的黄钾铁矾转化对相关 As(V)和 Sb(V)的迁移、形态和分配的影响。高浓度的 Fe（10 和 20 mM）在<10 分钟内迅速将黄钾铁矾转化为绿锈中间体，随后在 24 小时内沉淀出针铁矿。相比之下，较低浓度的 Fe（1 和 5 mM）导致了纤铁矿的形成。As K 边 XANES 光谱显示，在较高浓度的 Fe 存在下，部分 As(V)被还原为 As(III)，而 Sb L 边 XANES 光谱表明 Sb(V)没有被还原。转化过程增强了 Sb 在水相中的迁移能力，而 As 则重新分配到表面结合的可交换相中。研究结果表明，Fe 诱导的 As/Sb-黄钾铁矾的转化可以增加 Sb 的迁移能力，并对 As 的分配和形态产生重大影响。
