Mineralization of Diazinon with nanosized-photocatalyst TiO2 in water under sunlight irradiation: optimization of degradation conditions and reaction pathway.

The photocatalytic degradation of Diazinon under sunlight irradiation is investigated by using the nanosized photocatalyst TiO2. Eight intermediates are detected during the degradation, and the reaction pathway is proposed on the base of their intermediates. The degradation parameters, concerning photocatalyst concentration, temperature, pH, sunlight intensity and irradiation time are optimized. Under the optimal conditions, the photocatalytic degradation of Diazinon can be completed within 60 min. The photodegradation is found to follow the pseudo-first-order kinetic law at a rate constant of 0.068 min-1. The activation energy is 14.7 kJ/mol. The formations of sulphate, phosphate, nitrate and ammonium ions during the degradation are observed. About 83% of the initial N is detected as ammonium and nitrate ions during 50 h of irradiation time.