Arsenic removal by iron hydroxides, produced by enhanced corrosion of iron

Results of lab-scale experiments for arsenic removal from drinking water are presented. Arsenate(V)-ions were adsorbed on ferric hydroxides which were formed in-situ by corrosion of elemental iron in oxygenated water. Natural corrosion of fine iron wool was suitable to remove effectively high but realistic arsenic concentrations of 500 μg/L from drinking water. As the corrosion rate decreased significantly in time, two different methods to enhance the corrosion were tested and evaluated: galvanic corrosion using iron-copper contact elements and the application of an external voltage. The iron-copper contact elements showed promising results (a high and stable corrosion rate) but were bearing the risk of copper release when the contact broke down. The application of voltage led to an enhanced release of iron-ions but was coupled with a cathodic formation of hydrogen from water. The generation of hydrogen is a very undesirable effect for any practical application. Irrespective of the mode of corrosion, a post-treatment step (sand filtration) was required to remove the arsenic loaded rust particles from the effluent. In the final effluent, drinking water quality was reached by all the methods.