Contamination of water by arsenic both as a result of natural and anthropogenic processes poses a major threat to human health and to the environment in general. Where arsenic occurs as As(III), typical treatment involves peroxide oxidization to As(V), followed by coprecipitation and adsorption with iron(III). Because iron(II) commonly occurs concomitantly with arsenic in contaminated water, these waters have the potential to be self-treating when the Fe(II) oxidises and precipitates. However, As(III) oxidises much more slowly than Fe(II) at circumneutral pH. and As(III) does not coprecipitate to the same extent as As(V). A recently emerging technology for arsenic removal from drinking water in lesser developed countries involves the addition of citric acid to the Fe(II)/As(III) bearing water in the presence of sunlight. This has been found to promote the oxidation and coprecipitation of arsenic with iron.
The aim of this paper is to examine this promising treatment technology further.
