Arsenic Speciation: Reduction of Arsenic(v) to Arsenic(iii) by Fulvic Acid

Tsanangurayi Tongesayi; Ronald B. Smart

doi:10.1071/EN05095

RESEARCH ARTICLE

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Arsenic Speciation: Reduction of Arsenic(v) to Arsenic(iii) by Fulvic Acid

Tsanangurayi Tongesayi ^A and Ronald B. Smart ^A ^B

+ Author Affiliations

- Author Affiliations

^A West Virginia University Department of Chemistry, PO Box 6045, Morgantown, WV 26506-6045.

^B Corresponding author. Email: rsmart@wvu.edu

Environmental Chemistry 3(2) 137-141 https://doi.org/10.1071/EN05095
Submitted: 2 December 2005 Accepted: 23 February 2006 Published: 5 May 2006

Environmental Context. Most technologies for arsenic removal from water are based on the oxidation of the more toxic and more mobile arsenic(iii) to the less toxic and less mobile arsenic(v). As a result, research effort has been focussed on the oxidation of arsenic(iii) to arsenic(v). It is equally important to explore environmental factors that enhance the reduction of arsenic(v) to arsenic(iii). An understanding of the redox cycling of arsenic could result in the development of cheaper and more efficient arsenic removal technologies, especially for impoverished communities severely threatened by arsenic contamination.

Abstract. The objective of this study was to investigate the reduction of inorganic arsenic(v) with Suwannee River fulvic acid (FA) in aqueous solutions where pH, [FA], [As(v)], [As(iii)], and [Fe(iii)] were independently varied. Samples of inorganic As(v) were incubated with FA in both light and dark at constant temperature. Sterilisation techniques were employed to ensure abiotic conditions. Aliquots from the incubated samples were taken at various time intervals and analysed for As(iii) using square-wave cathodic-stripping voltammetry at a hanging mercury drop electrode. The study demonstrated the following important aspects of As speciation: (1) FA can significantly reduce As(v) to As(iii); (2) reduction of As(v) to As(iii) is a function of time; (3) both dark and light conditions promote reduction of As(v) to As(iii); (4) Fe(iii) speeds up the reduction reaction; and (5) oxidation of As(iii) to As(v) is promoted at pH 2 more than at pH 6.

Keywords. : arsenic — dissolved organic matter — iron — reduction — speciation

Acknowledgements

Financial support provided by the C. Eugene Bennett Department of Chemistry is greatly appreciated.

References

Arsenic Speciation: Reduction of Arsenic(v) to Arsenic(iii) by Fulvic Acid

Acknowledgements

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