Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada.
Environ Sci Technol. 2020 Apr 7;54(7):4006-4015. doi: 10.1021/acs.est.9b06250. Epub 2020 Mar 16.
Vanadium contamination is a growing environmental hazard worldwide. Aqueous vanadate (HVO) concentrations are often controlled by surface complexation with metal (oxyhydr)oxides in oxic environments. However, the geochemical behavior of this toxic redox-sensitive oxyanion in anoxic environments is poorly constrained. Here, we describe results of batch experiments to determine kinetics and mechanisms of aqueous HVO (100 μM) removal under anoxic conditions in suspensions (2.0 g L) of magnetite, siderite, pyrite, and mackinawite. We present results of parallel experiments using ferrihydrite (2.0 g L) and Fe (200 μM) for comparison. Siderite and mackinawite reached near complete removal (46 μmol g) of aqueous vanadate after 3 h and rates were generally consistent with ferrihydrite, whereas magnetite removed 18 μmol g of aqueous vanadate after 48 h and uptake by pyrite was limited. Removal during reaction with Fe was observed after 8 h, concomitant with precipitation of secondary Fe phases. X-ray absorption spectroscopy revealed V(V) reduction to V(IV) and formation of bidentate corner-sharing surface complexes on magnetite and siderite, and with Fe reaction products. These data also suggest that V(IV) is incorporated into the mackinawite structure. Overall, we demonstrate that Fe(II)-bearing phases can promote aqueous vanadate attenuation and, therefore, limit dissolved V concentrations in anoxic environments.
钒污染是全球范围内日益严重的环境危害。在含氧环境中，通常通过与金属（氧）氢氧化物表面络合来控制水合钒酸盐（HVO）的浓度。然而，这种有毒的氧化还原敏感的含氧阴离子在缺氧环境中的地球化学行为还受到很大限制。在这里，我们描述了分批实验的结果，以确定在磁铁矿、菱铁矿、黄铁矿和磁黄铁矿悬浮液（2.0 g L）中缺氧条件下 100 μM 水合 HVO 的去除动力学和机制。我们还介绍了使用水铁矿（2.0 g L）和 Fe（200 μM）进行平行实验的结果。菱铁矿和磁黄铁矿在 3 小时内几乎完全去除（46 μmol g）水合钒酸盐，而速率通常与水铁矿一致，而磁铁矿在 48 小时内去除 18 μmol g 的水合钒酸盐，黄铁矿的吸收有限。与 Fe 反应时观察到去除，同时沉淀出次生 Fe 相。X 射线吸收光谱表明 V(V)被还原为 V(IV)，并在磁铁矿和菱铁矿以及与 Fe 反应产物上形成双齿顶角共享表面络合物。这些数据还表明 V(IV)被掺入磁黄铁矿结构中。总的来说，我们证明了含 Fe(II)的相可以促进水合钒酸盐的衰减，从而限制缺氧环境中溶解 V 的浓度。
