Direct reduction of As(V) physically attached to a graphite electrode mediated by Fe(III)
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As(V) is electrochemically reduced on the surface of a carbonaceous electrode in the presence of hematite and hydrochloric acid 1 M. The influence of other iron oxides (goethite and limonite) was also tested, although they did not provided better results. The potential required to achieve the reduction must be lower than −0.3 V. The anodic voltammograms exhibit a peak at 0.14 V which corresponds to the oxidation of the As° previously generated during the pre-treatment step (−1 V, 5 s) to As(III). Fe(II) generated during the pre-treatment step plays a relevant role in the final reduction to As° which is subsequently reoxidized to As(III) in the anodic scan. This has been applied to the direct detection of 5 mg kg−1 of arsenic in a solid sample of compost with high concentration of iron oxides by square wave voltammetry.
KeywordsArsenic Reduction Iron oxides Electrochemistry Voltammetry
This work was supported by the SGPCCC of the Spanish Ministry of the Environment.
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