Electrochemical abatement of chloroethanes in water: Reduction, oxidation and combined processes

An electrochemical route, based on the anodic oxidation to carbon dioxide coupled with the cathodic reduction to de-halogenated hydrocarbons, was proposed for the treatment of waters contaminated by chloroethanes. The electrochemical abatement of two model compounds, namely 1,2-dichloroethane and 1,1,2,2-tetrachloroethane, was carried out by cathodic reduction at silver, anodic oxidation at boron doped diamond (BDD) and combined processes. The anodic oxidation gives rise to a high abatement of the concentration of both these compounds and of COD. The reduction of 1,1,2,2-tetrachloroethane proceeds also with high abatement but with the formation of some halogenated intermediates and final products, even if in low concentrations. Lower abatements were, on the other hand, obtained for the reduction of 1,2-dichloroethane. When reduction and oxidation processes were carried out simultaneously, a higher abatement of pollutants was obtained with the same amount of the passed charge (e.g., passed time) and applied cell voltage with respect to uncoupled processes. Furthermore, in the case of 1,1,2,2-tetrachloroethane, no other halogenated products were detected at the end of the electrolyses when the combined process was performed in an undivided cell.