Arsenic and fluoride removal from groundwater by electrocoagulation using a continuous filter-press reactor

We investigated simultaneous arsenic and fluoride removal from ground water by electrocoagulation (EC) using aluminum as the sacrificial anode in a continuous filter-press reactor. The groundwater was collected at a depth of 320 m in the Bajio region in Guanajuato Mexico (arsenic 43 mu g L-1, fluoride 2.5 mg L-1, sulfate 89.6 mg L-1, phosphate 1.8 mg L-1, hydrated silica 112.4 mg L-1, hardness 9.8 mg L-1, alkalinity 31.3 mg L-1, pH 7.6 and conductivity 993 mu S cm(-1)). EC was performed after arsenite was oxidized to arsenate by addition of 1 mg L-1 hypochlorite. The EC tests revealed that at current densities of 4, 5 and 6 mA cm(-2) and flow velocities of 0.91 and 1.82 cm s(-1), arsenate was abated and residual fluoride concentration satisfies the WHO standard (C-F < 1.5 mg L-1). Spectrometric analyses performed on aluminum flocs indicated that these are mainly composed of aluminum-silicates of calcium and magnesium. Arsenate removal by EC involves adsorption on aluminum flocs, while fluoride replaces a hydroxyl group from aluminum aggregates. The best EC,was obtained at 4 mA cm(-2) and 1.82 cm s(-1) with electrolytic energy consumption of 0.34 KWh m(-3). (C) 2015 Elsevier Ltd. All rights reserved.