Electromigration of arsenic and co-existing metals in mine tailings.

The aim of this study was to investigate the feasibility of enhanced electrokinetic remediation technology for controlled leaching and collection of labile arsenic fractions from mine tailings. Direct current was applied to tailings for 20 d using ammonium oxalate and sodium hydroxide as enhancement solutions. Migration of arsenic was observed, resulting in 63-71% removal near the cathode but only 6-17% overall removal in the entire tailings matrix in 20 d. However, significant migration of arsenic towards the anode and accumulation in a collection well near the anode was observed, especially under alkaline conditions. Thus, treatment time and consumption of chemicals could probably be reduced by installing specific collection or adsorption zones near the anode. A relationship between electrokinetic mobility of arsenic and other elements and their extractability in sequential extraction tests was established, indicating that dissolution or desorption of the elements and thermodynamic conditions (pH and Eh gradient) played a bigger role in the electrokinetic removal process than electromigration of soluble ions.