Simultaneous redox conversion of chromium(VI) and arsenic(III) under acidic conditions

Zhaohui Wang, Richard T. Bush, Leigh A. Sullivan, Jianshe Liu

Research output: Contribution to journalArticle

60 Citations (Scopus)

Abstract

Arsenic and chromium are often abundant constituents of acid mine drainage (AMD) and are most harmful as arsenite (As(III)) and hexavalent (Cr(VI)). To simultaneously change their oxidation state from As(III) to As(V), and Cr(VI) to Cr(III), is a potentially effective and attractive strategy for environmental remediation. The coabundance of As(III) and Cr(VI) in natural environments indicates their negligible direct interaction. The addition of H 2O2 enables and greatly accelerates the simultaneous oxidation of As(III) and reduction of Cr(VI). These reactions are further enhanced at acidic pH and higher concentrations of Cr(VI). However, the presence of ligands (i.e., oxalate, citrate, pyrophosphate) greatly retards the oxidation of As(III), even though it enhances the reduction of Cr(VI). To explain these results we propose a reaction mechanism where Cr(VI) is primarily reduced to Cr(III) by H2O2, via the intermediate tetraperoxochromate Cr(V). Cr(V) is then involved in the formation of OH radicals. In the presence of ligands, the capacity of Cr(V) to form OH radicals, which are primarily responsible for As(III) oxidation, is practically inhibited. Our findings demonstrate the feasibility for the coconversion of As(III) and Cr(VI) in AMD and real-world constraints to this strategy for environmental remediation.

Original languageEnglish
Pages (from-to)6486-6492
Number of pages7
JournalEnvironmental Science and Technology
Volume47
Issue number12
DOIs
Publication statusPublished - 2013
Externally publishedYes

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