Studies on three-dimensional electrode of granular activated carbons on the removal of fluoride in drinking water

Key words: 
• removal of fluoride /
• granular activated carbon /
• threedimensional /
• electrochemically enhanced adsorption

Abstract: Activated carbons as threedimensional electrodes were prepared to adsorb fluoride in drinking water. The electrosorption capacity of activated carbon electrodes with different bias potentials were measured, and the electrosorption kinetics were also investigated. The results showed that electrosorption can effectively increase the adsorption capacity from 3 V to 5 V. With electrosorption of activated carbons from aqueous solution, a 30 percent enhancement of adsorption capacity was achieved at 5 V, compared with the adsorption capacity at 0 V. Meanwhile，the electrosorption of threedimensional electrodes followed the firstorder adsorption kinetics. The electrosorption capacity exhibits a variety of responses depending on bias potential, pH, electrolyte，fluoride concentration and flow rate. The initial and saturated activated carbons were characterized using scanning electron micrograph (SEM) and nitrogen adsorption. The SEM micrographs show that the surface of activated carbons are not oxidized. The nitrogen adsorption suggests that the average pore which interacts electroption has no significant change before and after adsorption. These experimental results suggest that the threedimensional electrode can effectively improve the adsorption capacity of activated carbons, which may be due to they produce electric double layer capacitance instead of the oxidation on the surface of activated carbons or in the solution.