Photosensitized chlorobenzene degradation by UV/H2O2 oxidation

The degradation of chlorobenzene (CB) in UV/H2O2 system in aqueous solution, at pH 7, was studied. CB degradation was monitored by gas chromatography, Cl- liberation was monitored by ion chromatography at various irradiation times and a pseudo-first order kinetic in respect to both components was found. The rate constant k(Cl)(-) was lower than k(CB), which suggests that chlorinated intermediates are firstly formed by the attack of center dot OH radicals on CB, followed by chlorine liberation. When the CB concentration was kept constant we found a linear increase in the rate constants with H2O2 concentration, followed by a short interval with unmodified k(I) values and a decrease at higher H2O2 concentration. The variation of CB concentration at constant ratio [H2O2]/[CB] led to the decrease in the degradation efficiency due to the competition with the intermediates, for center dot OH radicals consumption. Our kinetic results agreed with the literature information on the CB degradation mechanism.