ABSTRACT
Granular activated carbon (GAC) has been widely used to remove hydrophobic organic compounds from water and wastewater due to its high adsorptive capacity. Phenolic compounds, however, are quite sensitive to one-electron oxidation to form phenoxy radicals, which can couple to form dimers and polymers. GAC is well known to promote oxidative reactions of both inorganic and organic species, particularly phenols. 1 These reaction products may be health hazards; chlorinated phenols, for example, can be oxidized by various pathways to chlorohydroxybiphenyls, chlorinated biphenyl ethers, chlorinated dibenzofurans, chlorinated dibenzodioxins, chloroquinones, and many other compounds. Phenolic dimers have been observed in GAC extracts after phenols were adsorbed on virgin or disinfectant-treated GAC surfaces. 2 , 4 We report that coupling reactions of phenol are partially suppressed when GAC is treated with humic materials or the phenolic acid, syringic acid.
