Adsorption characteristics of trace levels of bromate in drinking water by modified bamboo-based activated carbons

This study was undertaken to investigate the adsorption kinetics and isotherms of bromate (BrO3-) on bamboo charcoals that are activated with nitrogen and water vapor. Bamboo-based activated carbon (AC) was dipped in acid and oxidized in a mixture of potassium permanganate and sulfuric acid. Oxidation treatment considerably improved the physicochemical properties of AC, including purity, pore structure and surface nature, significantly enhancing BrO3- adsorption capacity. AC with many oxygenated groups and a high mesopore volume exhibited a particularly favorable tendency for BrO3- adsorption. Its adsorption of BrO3- is best fitted using Langmuir isotherm, and forms a monolayer. A kinetic investigation revealed that the adsorption of BrO3- by the ACs involved chemical sorption and was controlled by intra-particle diffusion. The competitive effects of natural organic matter (NOM) on AC were evaluated, and found to reduce the capacity of carbon to adsorb BrO3-. Residual dissolved ozone reacted with AC, reducing its capacity to absorb BrO3-. Proper dosing and staging of the ozonation processes can balance the ozone treatment efficiency, BrO3- formation, and the subsequent removal of BrO3-.