Adsorption of Bromate From Aqueous Solutions by Modified Granular Activated Carbon: Batch and Column Tests

Bromate by-product formation during ozonation of bromide-containing potable water has aroused widespread concern. In this study, cetylpyridinium chloride was selected to modify two different kinds of granular activated carbon (GAC) to improve their bromate adsorption capacity. The adsorption characteristics of modified GAC were studied by batch and column tests, with results suggesting greatly improved bromate adsorption ability: the saturation capacities for bromate were >7 times for modified GAC than for GAC under the experimental conditions used. This enhancement in adsorptive capacity is likely due to an increase in basic functional groups, because the saturated adsorption capacity of bromate on the GAC is positively correlated with the basic functional groups. The increase of the basic functional groups accelerates OH- dissociation from the GAC surface and protonation of the GAC surface, thus resulting in the enhancement in adsorptive capacity. The modified GAC was relatively immune to the impact of pH change over a broad range. Both the Yoon-Nelson model and the Thomas model fit well the breakthrough curves of bromate adsorbed by modified and unmodified GAC under different conditions. Our results provide insight into the sorption process of bromate onto modified GAC.