School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006, China.
Department of Atmospheric & Oceanic Sciences, McGill University, Montreal, PQ H3A 0B9, Canada; Department of Chemistry, McGill University, Montreal, PQ H3A 0B8, Canada.
J Hazard Mater. 2021 Apr 15;408:124423. doi: 10.1016/j.jhazmat.2020.124423. Epub 2020 Oct 31.
Ferrihydrite is ubiquitous in natural environments and is usually co-precipitated with impure ions and toxic contaminants like Al(III) and Sb(V) during the neutralization process of acid mine drainage. However, little is known about the dynamic interactions among ferrihydrite, Al(III) and Sb(V). In this study, the influence of coprecipitated Al(III) and Sb(V) on the transformation of ferrihydrite was investigated. The samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy before and after aging for 10 days at 70 °C. Results indicated that the Al(III) enhanced the immobilization of Sb(V) under neutral and alkaline conditions, and the presence of Sb(V) induced more production of extractable Al(III). XRD patterns revealed that the transformation rate of coprecipitated Al(III) and Sb(V) ferrihydrite was higher than Al-coprecipitated ferrihydrite. It is speculated that the presence of Sb(V) weakened the inhibition of Al(III) under experimental conditions. Competitive reaction of Al(III) and Sb(V) for substitution on the lattice Fe of ferrihydrite, likely decreased Al(III) substitution on ferrihydrite, and thus increased the observed transformation rate of ferrihydrite. These results have significant environmental implications for predicting the role of impurities and contaminants on ferrihydrite transformation processes.
水铁矿在自然环境中普遍存在，通常在中和酸性矿山排水过程中与不纯离子和有毒污染物（如 Al(III) 和 Sb(V)）共沉淀。然而，对于水铁矿、Al(III) 和 Sb(V) 之间的动态相互作用知之甚少。在这项研究中，研究了共沉淀的 Al(III) 和 Sb(V) 对水铁矿转化的影响。样品在 70°C 下老化 10 天后，通过 X 射线衍射 (XRD)、拉曼光谱、傅里叶变换红外光谱、X 射线光电子能谱和透射电子显微镜进行了表征。结果表明，在中性和碱性条件下，Al(III) 增强了 Sb(V) 的固定化，而 Sb(V) 的存在诱导了更多可提取 Al(III) 的产生。XRD 图谱表明，共沉淀的 Al(III) 和 Sb(V) 水铁矿的转化速率高于 Al 共沉淀水铁矿。推测在实验条件下 Sb(V) 的存在削弱了 Al(III) 的抑制作用。Al(III) 和 Sb(V) 在水铁矿晶格 Fe 上的竞争取代反应，可能降低了 Al(III) 在水铁矿上的取代，从而增加了水铁矿的观察转化速率。这些结果对预测杂质和污染物对水铁矿转化过程的作用具有重要的环境意义。
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