Oxidation of chlorothalonil in aqueous solution by means of UV, H ₂O ₂/UV, oxalate/UV, and oxalate-assisted H ₂O ₂/UV irradiation

The degradation of chlorothalonil was explored using UV, H ₂O ₂/UV, Oxalate/UV, and oxalate-assisted H ₂O ₂/UV irradiation. The optimum initial hydrogen peroxide and oxalate concentrations in the photolysis were about 100 mg L ^-1 and 1 mM, respectively. The optimum pseudo-first-order reaction rate constants for UV (k _UV), H ₂O ₂/UV (kH ₂O ₂), oxalate/UV (k _oxalate), and oxalate-assisted H ₂O ₂/UV (kH ₂O _2-oxalate) irradiation processes were 0.186, 0.357, 0.520, and 1.806 min ^-1, respectively. A TOC analysis of the solution indicates that chlorothalonil is largely decomposed to carbon dioxide by the oxalate-assisted H ₂O ₂/UV irradiation process. In our experiments, the oxalate-assisted H ₂O ₂/UV irradiation process was the most effective method for the degradation of chlorothalonil relative to the use of UV alone or the H ₂O ₂/UV irradiation processes.