Aerobic oxidation of mackinawite (FeS) and its environmental implication for arsenic mobilization
Aerobic oxidation of mackinawite (FeS) and its environmental implication for arsenic mobilization
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DOI：
10.1016/j.gca.2010.03.012
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发表时间：
2010-06-01
影响因子：
5
通讯作者：
Hayes, Kim F.
中科院分区：
文献类型：
--
作者：
Jeong, Hoon Y.;Han, Young-Soo;Hayes, Kim F.
在氧化条件下，研究了砷的氧化和砷的同时动员作为pH值的函数。在酸性条件下，FeS的氧化主要是由质子促进溶解引发的，导致Fe（II）和硫化物的释放。虽然大部分溶解的硫化物在被氧化之前挥发，但溶解的Fe（II）被氧化成绿色锈状沉淀物和针铁矿（α-FeOOH）。在碱性pH下，FeS表面上的Fe（III）（oxyhydr）氧化物涂层的发展抑制了FeS溶解后的溶液相氧化。相反，FeS主要通过表面介导的氧化作用氧化成纤铁矿（γ-FeOOH），而不溶解。在中性pH下，FeS通过FeS溶解后的溶液相氧化和表面介导的氧化机制被氧化。砷在硫化亚铁氧化过程中的移动受到硫化亚铁氧化机制的强烈影响。在酸性条件下（在一定程度上在中性条件下），FeS的快速溶解和Fe（oxyhydr）氧化物的缓慢沉淀导致砷在水中的积累。相反，FeS在碱性pH下的表面介导的氧化导致Fe（oxyhydr）氧化物的直接形成，其在好氧条件下为As提供有效的吸附剂。在酸性和中性pH下，溶解的Fe（II）的液相氧化加速了吸附性较低的As（III）氧化为吸附性较高的As（V）。本研究表明，砷的氧化活化可能是硫化物沉积物孔隙水砷富集的一个重要途径。(C)2010爱思唯尔有限公司版权所有。
Oxidation of mackinawite (FeS) and concurrent mobilization of arsenic were investigated as a function of pH under oxidizing conditions. At acidic pH, FeS oxidation is mainly initiated by the proton-promoted dissolution, which results in the release of Fe(II) and sulfide in the solution. While most of dissolved sulfide is volatilized before being oxidized, dissolved Fe(II) is oxidized into green rust-like precipitates and goethite (alpha-FeOOH). At basic pH, the development of Fe(III) (oxyhydr)oxide coating on the FeS surface inhibits the solution-phase oxidation following FeS dissolution. Instead, FeS is mostly oxidized into lepidocrocite (gamma-FeOOH) via the surface-mediated oxidation without dissolution. At neutral pH, FeS is oxidized via both the solution-phase oxidation following FeS dissolution and the surface-mediated oxidation mechanisms. The mobilization of arsenic during FeS oxidation is strongly affected by FeS oxidation mechanisms. At acidic pH (and to some extent at neutral pH), the rapid FeS dissolution and the slow precipitation of Fe (oxyhydr)oxides results in arsenic accumulation in water. In contrast, the surface-mediated oxidation of FeS at basic pH leads to the direct formation of Fe (oxyhydr)oxides, which provides effective adsorbents for As under oxic conditions. At acidic and neutral pH, the solution-phase oxidation of dissolved Fe(II) accelerates the oxidation of the less adsorbing As(III) to the more adsorbing As(V). This study reveals that the oxidative mobilization of As may be a significant pathway for arsenic enrichment of porewaters in sulfidic sediments. (C) 2010 Elsevier Ltd. All rights reserved.