Comparative Study on Electrochemical Treatment of Arsenite: Effects of Process Parameters, Sludge Characterization and Kinetics

This study involves the application of electrocoagulation process to remove arsenite from simulated groundwater using steel, aluminium, platinum and glassy carbon in a 2-L batch reactor setup. It was observed that arsenite was initially oxidized to arsenate. In the case of glassy carbon and platinum electrodes, arsenate build-up was found in the solution due to the lack of floc formation. However, in the case of steel and aluminium electrodes, the flocs generated effectively adsorbed the arsenate produced. Parametric studies reveal the highest removal efficiency of arsenite at low pH, high current and low concentration, with the optimum removal according to surface response methodology achieved at pH 4, 1.2 A and 10 ppm. Electrical energy consumption evaluation shows that operating at the optimum conditions, 653.33 kWh/kg is required to achieve WHO limit from an initial arsenite concentration of 10 ppm. Kinetic studies indicate that the rate is best described by first-order model. The sludges obtained after the electrocoagulation process using the steel and aluminium electrodes further reveal the adsorption of arsenic species onto the metal hydroxide surfaces.