Bromate reduction and reaction-enhanced perchlorate adsorption by FeCl3-impregnated granular activated carbon

Abstract

This work studied simultaneous bromate (BrO3−) reduction and adsorption of perchlorate (ClO4−) by FeCl3-impregnated granular activated carbon (Fe-GAC) and the mutual co-solute effects. We report that BrO3− reduction by Fe-GAC was coupled with enhanced adsorption of ClO4− by the material. The Langmuir maximum adsorption capacity for ClO4− by Fe-GAC was increased from 0.179 mmol g−1 (without BrO3−) to 0.256 mmol g−1 in the presence of 0.2 mmol L−1 of BrO3− (a 43% increase) at pH 6.0. While the activated carbon alone was able simultaneously remove both BrO3− and ClO4−, Fe-GAC offered much greater removal efficacy and synergistic effect, likely because the immobilized Fe3+ acted as a catalyst and provided a local acidic environment, both being in favor of accelerated BrO3− reduction. Mechanistic analyses revealed that BrO3− removal was through a two-step process: ion exchange with OH− and Cl− on Fe-GAC, and then Fe-catalyzed reduction of BrO3− to Br− by carbon. The carbon-BrO3- redox reaction generated more Fe-O and C-O groups on the material surface, which can bind with ClO4− by surface complexation and electrostatic interactions. To our knowledge, this is the first report that metal modified activated carbon may facilitate synergistic removal of both BrO3− and ClO4−, which are common co-solutes in contaminated waters.