Chromium(VI) removal by siderite (FeCO3) in anoxic aqueous solutions: An X-ray absorption spectroscopy investigation
Chromium(VI) removal by siderite (FeCO3) in anoxic aqueous solutions: An X-ray absorption spectroscopy investigation
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DOI：
10.1016/j.scitotenv.2018.06.003
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发表时间：
2018-11-01
影响因子：
9.8
通讯作者：
Burton, Edward D.
中科院分区：
文献类型：
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作者：
Bibi, Irshad;Niazi, Nabeel Khan;Burton, Edward D.
六价铬是一种需要重点关注的环境污染物，可以通过将有毒的六价铬还原为无毒的三价铬来处理。菱铁矿 (FeCO3) 是一种含 Fe(II) 的矿物，存在于许多厌氧沉积物和地下水系统中，并且具有极高的反应性，因此使其成为控制 Cr(VI) 在一系列缺氧水环境中的归宿和迁移的潜在重要宿主相。在这里，我们研究了菱铁矿吸附和还原过程中 Cr(VI) 的命运，以及严格无氧条件下 Cr(VI) 反应的菱铁矿的形态随不同 pH (4-10) 和初始 Cr(VI) 浓度 (0.5-10 mM) 的变化。值得注意的是，初始添加的 Cr(VI) 水溶液 (0.5-10 mM) 在 pH 4 和 5 时分别有高达 97% 和 91% 被还原为 Cr(III)。然而，菱铁矿对 Cr(VI) 的还原效率在 pH 值 6 至 10 范围内（与 90% Cr(III) 相似）略有下降，仅在初始 Cr(VI) 浓度为 0.5-1.5 mM 时。铬 K 边 XANES 光谱证实，在 pH 5、7 和 9 下与低 (2 mM) 和高 (10 mM) 初始 Cr(VI) 浓度的菱铁矿平衡后，吸附的 Cr(VI) 完全还原为 Cr(III)。此外，固相样品的 Fe K 边 XANES 和 EXAFS 光谱表明，在与pH 7 和 9 时的 Cr(VI) 含量，而 pH 5 时的低 Cr(VI) 处理仅保留 24%。结果表明，在缺氧水条件下，菱铁矿可以帮助固定 Cr(VI) 并使其解毒，这些耦合吸附和氧化还原反应的程度由初始 Cr(VI) 浓度和 pH 值控制。 (c) 2018 Elsevier B.V. 保留所有权利。
Chromium(VI) is an environmental contaminant of priority concern, which can be treated by reduction of toxic Cr(VI) to non-toxic Cr(III). Siderite (FeCO3), an Fe(II)-containing mineral, occurs in many anaerobic sediments and groundwater systems and is extremely reactive, thus making it a potentially important host-phase in governing the fate and transport of Cr(VI) in a range of anoxic aqueous environments. Here, we investigate the fate of Cr(VI) during sorption and reduction by siderite, as well as speciation of Cr(VI)-reacted siderite as a function of varying pH (4-10) and initial Cr(VI) concentrations (0.5-10 mM) under strictly oxygen-free conditions. Notably, up to 97% and 91% of initial added aqueous Cr(VI) (0.5-10 mM) was reduced to Cr(III) at pH 4 and 5, respectively. However, the reduction efficiency of Cr(VI) by siderite slightly decreased in the pH range from 6 to 10 (similar to 90% Cr(III)), only at 0.5-1.5 mM initial Cr(VI) concentrations. Chromium K-edge XANES spectroscopy confirmed the complete reduction of sorbed Cr(VI) to Cr(III) after equilibration of siderite with low (2 mM) and high (10mM) initial Cr(VI) concentrations at pH 5, 7 and 9. In addition, Fe K-edge XANES and EXAFS spectra of solid-phase samples showed that 74-78% and 78-89% of Fe remained as siderite, respectively, after equilibration with Cr(VI) at pH 7 and 9, whereas only 24% remained for the low Cr(VI) treatment at pH 5. The results imply that under anoxic aqueous conditions, siderite can help immobilize and detoxify Cr(VI) with the extent of these coupled sorption and redox reactions being controlled by initial Cr(VI) concentrations and pH. (c) 2018 Elsevier B.V. All rights reserved.