Schwertmannite is a poorly-crystalline Fe(III) oxyhydroxysulfate mineral that may control Sb(V) mobility in acid sulfate environments, including acid mine drainage and acid sulfate soils. However, the mechanisms that govern uptake of aqueous Sb(V) by schwertmannite in such environments are poorly understood. To address this issue, we examined Sb(V) sorption to schwertmannite across a range of environmentally-relevant Sb(V) loadings at pH 3 in sulfate-rich solutions. Antimony K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy revealed that Sb(V) sorption (at all loadings) involved edge and double-corner sharing linkages between SbO and FeO octahedra. The coordination numbers for these linkages indicate that sorption occurred by Sb(V) incorporation into the schwertmannite structure via heterovalent Sb(V)-for-Fe(III) substitution. As such, Sb(V) sorption to schwertmannite was not limited by the abundance of surface complexation sites and was strongly resistant to desorption when exposed to 0.1 M PO. Sorption of Sb(V) also conferred increased stability to schwertmannite, based on changes in the schwertmannite dissolution rate during extraction with an acidic ammonium oxalate solution. This study provides new insights into Sb(V) sorption to schwertmannite in acid sulfate environments, and highlights the role that schwertmannite can play in immobilizing Sb(V) within its crystal structure.

中文翻译：

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酸性硫酸盐环境中锑对施威特曼石的吸附


施威特曼石是一种结晶度较差的 Fe(III) 羟基硫酸盐矿物，可控制酸性硫酸盐环境（包括酸性矿山排水和酸性硫酸盐土壤）中的 Sb(V) 迁移率。然而，人们对施威特曼石在这种环境中吸收含水 Sb(V) 的机制知之甚少。为了解决这个问题，我们在富含硫酸盐的溶液中，在 pH 3 的条件下，研究了一系列与环境相关的 Sb(V) 负载量，Sb(V) 对施威特曼石的吸附情况。锑 K 边扩展 X 射线吸收精细结构 (EXAFS) 光谱表明，Sb(V) 吸附（在所有负载下）涉及 SbO 和 FeO 八面体之间的边缘和双角共享连接。这些键的配位数表明吸附是通过异价 Sb(V) 取代 Fe(III) 并入施威特曼石结构而发生的。因此，Sb(V)对施威特曼石的吸附不受表面络合位点丰度的限制，并且当暴露于 0.1 M PO 时对解吸有很强的抵抗力。基于酸性草酸铵溶液萃取过程中施威特曼石溶解速率的变化，Sb(V) 的吸附也提高了施威特曼石的稳定性。这项研究为酸性硫酸盐环境中 Sb(V) 吸附到施威特曼石提供了新的见解，并强调了施威特曼石在将 Sb(V) 固定在其晶体结构中所发挥的作用。