Catalytic decomposition of hydrogen peroxide and 4-chlorophenol in the presence of modified activated carbons

Abstract

The objective of this research was to examine the heterogeneous catalytic decomposition of H2O2 and 4-chlorophenol (4-CP) in the presence of activated carbons modified with chemical pretreatments. The decomposition of H2O2 was suppressed significantly by-the change of surface properties including the decreased pH(pzc) modified with oxidizing agent and the reduced active sites occupied by the adsorption of 4-CP. The apparent reaction rate of H2O2 decomposition was dominated by the intrinsic reaction rates on the surface of activated carbon rather than the mass transfer rate of H2O2 to the solid surface. By the detection of chloride ion in suspension, the reduction of 4-CP was not only attributed to the advanced adsorption but also the degradation of 4-CP. The catalytic activity toward 4-CP for the activated carbon followed the inverse sequence of the activity toward H2O2, suggesting that acidic surface functional group could retard the H2O2 loss and reduce the effect of surface scavenging resulting in the increase of the 4-CP degradation efficiency. Few effective radicals were expected to react with 4-CP for the strong effect of surface scavenging, which could explain why the degradation rate of 4-CP observed in this study was so slow and the dechlorination efficiency was independent of the 4-CP concentration in aqueous phase. Results show that the combination of H2O2 and granular activated carbon (GAC) did increase the total removal of 4-CP than that by single GAC adsorption. (C) 2003 Elsevier Science Ltd. All rights reserved.