OXIDATION-KINETICS AND MECHANISMS OF TRIHALOMETHANES BY FENTONS REAGENT

Oxidation kinetics and mechanisms of four trihalomethanes (THMs) commo nly found in chlorinated drinking water by Fenton's reagent were inves tigated. All the experiments were carried out in air-tight and well-mi xed batch reactors in which no headspace was allowed in order to minim ize volatilization of any THM during reaction. The optimum dosages of H2O2 and Fe2+ in the oxidation of bromoform was 3.7-1.9 mM for all the initial concentrations at pH 3.5. The maximum bromoform degradations of 85, 78 and 65% at 3 min were achieved for bromoform concentrations of 295, 98.3 and 49.2 mu g/l, respectively. The pseudo-first-order oxi dation constants of THMs increase with the increasing number of bromin e atoms present in a THM molecule, with bromoform being oxidized the f astest and bromodichloromethane being oxidized the slowest. No oxidati ve degradation of chloroform was oberved, because the losses in chloro form concentration during the oxidation experiments are the same as wh at was observed in control experiments. Experiments conducted on the T HM mixtures gave similar results in terms of extent of observed oxidat ive degradation, the amount of THM oxidized increased with increasing initial organic concentrations. The oxidation rate constants for each THM in the mixture also increased as the number of bromine atoms prese nt in a THM molecule increased, with bromoform exhibiting the Fastest kinetic rates and bromodichloromethane exhibiting the slowest kinetic rates. (C) 1997 Elsevier Science Ltd.