Title: Removal of microcystin-LR by UV/H_2O_2 photocatalytic oxidation
Abstract: The present article reports the authors' investigation on the degradation of microcystins on purpose to assess the effectiveness and feasibility of the combined UV/H_2O_2 catalytic system for the disinfection of water polluted by microcystins. Our experiment on the microcystins produced by cyanobacteria in micro-polluted water proves to be extremely potent in hepatotoxins, which may likely result in a potential health hazard for human beings if they drink the water. However, the microcystin-LR degraded by using the combined UV/H_2O_2 catalytic oxidation system proves that the water processed with our method will be safe enough to be a source of drinking water supply. In addition, we have also investigated the likely influencing factors, such as H_2O_2 dosage, pH values, UV light intensities, initial concentration of microcystin-LR and the reaction time on the degradation of microcystin-LR as well as its degradation kinetics of microcystin-LR based on the experimental data. The results show that the degradation of microcystin-LR follows a mechanism of direct photolysis and hydroxyl radical oxidation. The hydroxyl radical generated from the decomposition of hydroxyl peroxide is under the UV irradiation. The kinetics of microcystin-LR degradation in the combined UV/H_2O_2system follows both the pseudo-first-order equation and the second-order rate one. The rate constants obtained from the combined experimental data decreased and half-lives prolonged with the increasing concentration of the microcystin-LR. The degradation rate of microcystin-LR was to reach 80.8% under the experimental conditions of microcystin-LR concentration 0.203 mg/L, H_2O_2 dosage 1.0 mmol/L, with the reaction temperature (25.5±1) ℃, pH 6.8, UV light intensity 2.5×10~4 lux and reaction time 60 minutes respectively. While the rate constants of microcystin-LR degradation by UV/H_2O_2, UV and H_2O_2 action proves to be 0.030 6, 0.015 4 and 0.002 5 min~(-1)respectively. Therefore, the UV/H_2O_2combined process has markedly enhanced the degradation efficiency of microcystin-LR compared to the UV or H_2O_2 single treatment. The combined UV/H_2O_2 catalytic system therefore proves to be effective in removing microcystins from the micro-polluted surface water.
Publication Year: 2005
Publication Date: 2005-01-01
Language: en
Type: article
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Cited By Count: 1
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