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

摘要

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. (C) 2018 Elsevier Ltd. All rights reserved.