Photocatalytic oxidation of arsenic(III): Evidence of hydrozyl radicals

Arsenic contamination has been found in the groundwater of several countries. Photocatalysis can rapidly oxidize arsenite (As(III)) to less labile and less toxic arsenate (As(V)), which then can be removed by adsorption onto photocatalyst surfaces. This study investigates the photocatalytic oxidatio...

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Bibliographic Details
Published inEnvironmental science & technology Vol. 39; no. 6; p. 1827
Main Authors Dutta, Paritam K, Pehkonen, S O, Sharma, Virender K, Ray, Ajay K
Format Journal Article
LanguageEnglish
Published Easton American Chemical Society 15.03.2005
Subjects
Arsenic
Free radicals
Oxidation
Photocatalysis
Water purification
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Summary:Arsenic contamination has been found in the groundwater of several countries. Photocatalysis can rapidly oxidize arsenite (As(III)) to less labile and less toxic arsenate (As(V)), which then can be removed by adsorption onto photocatalyst surfaces. This study investigates the photocatalytic oxidation of As(III) to As(V) as a function of As(III) concentration, pH, catalyst loading, light intensity, dissolved oxygen concentration, type of TiO2 surfaces, and ferric ions to understand the kinetics and the mechanism of As(III) oxidation in the UV/TiO2 system. Photocatalytic oxidation of As(III) to As(V) takes place in minutes and follows zeroorder kinetics. Benzoic acid (BA) was used as a hydroxyl radical (OH) scavenger to provide evidence for the *OH as the main oxidant for oxidation of As(III). The *OH radical was independently generated by nitrate photolysis, and kinetics of As(III) oxidation by the *OH radical was determined. Formation of salicylic acid (SA) from the oxidation of BA by *OH also demonstrates the involvement of *OH in the mechanism of As(III) oxidation. The effect of Fe(III) on As(III) oxidation at different pH values with and without TiO2 under UV light was examined. The results suggest that *OH is the dominant oxidant for As(III) oxidation. Two commercially available TiO2 suspensions, Degussa P25 and Hombikat UV1001 were tested for the removal of arsenic through oxidation of As(III) to As(V) followed by adsorption of As(V) onto TiO2 surfaces. Results showed that complete removal of arsenic below the World Health Organization drinking water limit of 10mug/L could be achieved. [PUBLICATION ABSTRACT]
ISSN:0013-936X