Arsenic-containing pyrite oxidative dissolution can be a main cause of arsenic contamination in groundwater aquifers during natural or anthropogenic recharge with oxic water. During oxidation, iron(III) (hydr)oxides can form simultaneously as a secondary minerals and act a crucial sink for mobilized arsenic. This study has, therefore, examined the oxidative dissolution of arsenopyrite in the presence Fe3+(aq) at circumneutral pH. Interestingly, we have found that despite their low solubility, small quantities of Fe3+(aq) triggered electron transfer between Fe3+(aq) and Fe(II) in arsenopyrite, resulting in higher extents of secondary mineral formation and faster phase transformation. Dissolved arsenic concentrations were also elevated in these systems due to faster dissolution. Our findings indicate that for arsenic transport under changing redox conditions, interactions between Fe3+(aq) and arsenopyrite can be a crucial factor in predicting arsenic-bearing pyrite oxidation as well as iron(III) (hydr)oxide formation and stability.

Promotion of arsenopyrite dissolution and secondary mineral formation and phase transformation by aqueous Fe3+

251st National Meeting (2016)

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