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Tooeleite Transformation and Coupled As(III) Mobilization Are Induced by Fe(II) under Anoxic, Circumneutral Conditions
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2022-06-22 , DOI: 10.1021/acs.est.2c02130
Girish Choppala 1 , Dane Lamb 2 , Robert Aughterson 3 , Edward D Burton 4
Affiliation  

Tooeleite [FeIII6(AsIIIO3)4SO4(OH)4.4H2O] is an important As(III) host phase in diverse mining-impacted environments. Tooeleite has also received attention as a target phase for immobilizing As(III) in environmental and engineered settings. However, little is known regarding tooeleite’s environmental stability, with no previous research examining the possible role of Fe(II) in inducing tooeleite transformation (as occurs for Fe(III) oxide minerals). We investigated shifts in solid-phase Fe and As speciation and associated As mobilization into the aqueous phase during exposure of tooeleite to aqueous Fe(II) under anoxic conditions at pH 4 to 8. Our results demonstrate that environmentally relevant concentrations of aqueous Fe(II) (i.e., 1 to 10 mM) induce significant mobilization of As(III) from tooeleite under near-neutral pH conditions, with greater As(III) mobilization occurring at higher pH. Extended X-ray absorption fine structure spectroscopy at both the As and Fe K-edge reveals that the observed As(III) mobilization was coupled with partial Fe(II)-induced transformation of tooeleite to As(III)-bearing ferrihydrite at pH 6 to 8. These results provide new insights into the environmental stability of tooeleite and demonstrate a novel pathway for As(III) mobilization in tooeleite-bearing systems.

中文翻译:

Tooeleite 转化和偶联 As(III) 动员由 Fe(II) 在缺氧、环中性条件下诱导

Tooeleite [Fe III 6 (As III O 3 ) 4 SO 4 (OH) 4 .4H 2O] 是各种受采矿影响环境中重要的 As(III) 宿主相。Tooeleite 作为在环境和工程环境中固定 As(III) 的目标相也受到关注。然而,关于太长石的环境稳定性知之甚少,之前没有研究检查 Fe(II) 在诱导太长石转变中的可能作用(如 Fe(III) 氧化物矿物所发生的那样)。我们研究了固相 Fe 和 As 形态的变化以及在 pH 4 至 8 的缺氧条件下,在太橄榄石暴露于水性 Fe(II) 期间,As 向水相中的移动。我们的结果表明,与环境相关的水性 Fe(II) 浓度)(即 1 至 10 mM)在近中性 pH 条件下诱导太油石中 As(III) 的显着迁移,在较高的 pH 值下发生更大的 As(III) 迁移。As 和 Fe K 边缘处的扩展 X 射线吸收精细结构光谱表明,观察到的 As(III) 移动与部分 Fe(II) 诱导的太橄榄石在 pH 6 下转变为含 As(III) 的水铁矿相结合至 8. 这些结果提供了对太橄榄石环境稳定性的新见解,并展示了 As(III) 在含太橄榄石系统中的新途径。
更新日期:2022-06-22
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