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

Abstract 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 µg 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 µS 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 ). 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 .