Kinetics of tricyclazole photodegradation under UV and sunlight: Role of photocatalysts and photosensitizers

Direct and indirect photodegradation of tricyclazole (TRCZ) was studied in aqueous solution using newly developed UV system and sunlight. Effect of photocatalysts (TiO₂, ZnO and Fe₃O₄) and photosensitizers (KNO₃ and humic acid) on indirect TRCZ degradation as well effect of TRCZ/photocatalysts’ concentration, solution pH and photocatalyst reuse were evaluated. Compared to direct photolysis of TRCZ under UV (19.74%) and sunlight (16.42%), photocatalysts significantly enhanced indirect photodegradation of TRCZ, but effect varied with photocatalyst, its dose, solution pH, TRCZ concentration and source of irradiation. Among catalysts, TiO₂ (250 mg/L) was the best both under UV and sunlight and registered more than 98% TRCZ (5 mg/L) degradation after 2 h irradiation. The degradation efficiency of TRCZ increased with increasing photocatalysts’ concentration, and irradiation time, while decreased with increasing solution pH, and TRCZ concentration. Sensitizers KNO₃ and humic acid decreased efficiency of TiO₂. Grand Canonical Monte-Carlo simulation was used to simulate adsorption/association between TRCZ and photocatalyst/photosensitizer and TRCZ degradation. Repeated use of TiO₂ marginally decreased its activity with 8.13% decrease in TRCZ degradation was observed after 4 cycles. TRCZ degradation data under different treatments fitted best to the first-order kinetics. This study suggested that TiO₂ can be utilized for TRCZ degradation in water.