Removal of bromate ion using powdered activated carbon

Abstract

Bromate ion (BrO 3 −) removal from drinking water by powdered activated carbons (PAC S) in bath mode was evaluated under various operational conditions. Six kinds of PACs, including wood-based carbon, fruit-based carbon, coal-based carbon, and these three carbons thermally deoxidized in a nitrogen atmosphere, were selected to investigate their capacity on BrO 3 − removal. With the highest zeta potential value and being richly mesoporous, coal-based carbon had a high and an excellent BrO 3 − adsorption efficiency. The removal content of BrO 3 − by per gram of coal-based carbon was 0.45 mg within 5 hr in 100 μg/L bromate solution. The surface characteristics of PACs and bromide formation revealed that both physical and chemical PACs properties simultaneously affected the adsorption-reduction process. Under acidic conditions, PAC S possessed high zeta value and adequate basic groups and exhibited neutral or positive charges, promoting BrO 3 − adsorption-reduction on the carbon surface. Interestingly, the PAC S thermally deoxidized in N 2 atmosphere optimized their properties, e.g. increasing their zeta values and decreasing the oxygen content which accelerated the BrO 3 − removal rate. The maximum adsorption capacity of fruit-based carbon was the highest among all tested carbons (99.6 mg/g), possibly due to its highest pore volume. Remarkably, the thermal regeneration of PACs in N 2 atmosphere could completely recover the adsorption capacity of PACs. The kinetic data obtained from carbons was analyzed using pseudo second-order and intraparticle diffusion models, with results showing that the intraparticle diffusion was the more applicable model to describe adsorption of BrO 3 − onto PACs.