The World Health Organization categorizes inorganic arsenic (As) as the most globally significant inorganic chemical contaminant in drinking water; new global risk estimates suggest that as many as 220 million people spanning 50 countries are consuming water containing hazardous concentrations of As (&gt;10µg/L). While progress has been made to understand the origins and effects of this contamination, more work is needed to elucidate how As is mobilized in groundwater. One of the principal mechanisms by which As is released into the environment is through interactions with mineral oxides present in soils and sediments. Considered some of the strongest naturally occurring oxidizing agents, manganese(III/IV) oxides (MnOx) affect the movement of As in groundwater by oxidizing more-mobile, more-toxic As(III) to less-mobile, less-toxic As(V). However, the reaction mechanism and associated rate constants remain elusive, and a recent analysis demonstrated that previous efforts to characterize the extent and rate of As interactions with MnOx are inconsistent. Via a combination of batch and in situ experiments, this work seeks to examine the role of Mn(III) content in δ-MnOx as it relates to As sorption and oxidation.

Examining the role of average manganese oxidation state in limiting the oxidative transformation of As(III) by δ-MnO2

ACS Spring 2022

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