Degradation of Malathion and Parathion by Ozonation, Photolytic Ozonation, and Heterogeneous Catalytic Ozonation Processes

摘要

The oxidation of organophosphorus pesticides (OPPs), such as malathion and parathion, in aqueous solution was studied using conventional ozonation (O_3), photolytic ozonation (O_3/UV, O_3/UV/H_2O_2), and heterogeneous catalytic ozonation (O_3/TiO_2/UV) processes. Experiments were performed in batch mode at laboratory scale and processes were compared in terms of disappearance kinetics. The best results of pesticide mineralization were obtained when TiO_2 particles in combination with ozone (O_3) and UV photolysis (λ = 254 nm) were applied. Decomposition of 99% of parent compounds were achieved in 10 min and oxon derivatives were completely removed in 30 min. The initial reaction rate increases linearly with increasing catalyst amount. Toxicity measurements of the treated solutions were carried out in order to evaluate the efficiency of the treatment methods. No detoxification was achieved for O_3 and O_3/UV applications. Heterogeneous photocatalytic ozonation was shown to be feasible for achieving complete decomposition of OPPs and their oxon intermediates.