|
|||||
|
|
Aerobic oxidation of mackinawite (FeS) and its environmental implication for arsenic mobilization |
|
| Authors: | Hoon Y Jeong Sung W Park |
| Institution: | a Pohang Accelerator Laboratory, Pohang University of Science and Technology (POSTECH), Pohang 790784, Republic of Korea b Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, MI 48109, USA c Geological and Environmental Hazards Division, Korea Institute of Geoscience & Mineral Resources, Daejeon 305-350, Republic of Korea |
| Abstract: | 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 (α-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 (γ-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. |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ | |