Sonochemical, photocatalytic and sonophotocatalytic oxidation of flonicamid pesticide solution using different catalysts

Abstract

Combination approaches involving sonolysis and photolysis with catalysts like CuO, ZnO and TiO2 have been applied for the treatment of commercial Flonicamid solution. The effect of ultrasonic power, initial loading of flonicamid and pH on COD reduction was studied for individual sonolysis and photolysis. The optimal conditions were established as initial concentration of 75 ppm, US power of 100 W and pH as 2. The impact of catalyst concentration has been subsequently examined and optimized loading were established for different catalysts as CuO (1 g/l), ZnO (0.75 g/l) and TiO2 (0.75 g/l). The extent of COD reduction achieved using ultrasound combination with catalyst at optimum loading was found to be 62.07 %, 73.73 % and 77.59 % for CuO, ZnO and TiO2 catalysts respectively. The efficiency of sonocatalytic treatment process was greater (COD removal as 77.59 % for specific case of TiO2 catalyst) than sonolysis (39.23 %) operated individually. Similar trend was also seen for comparison of photocatalysis with photolysis. Sonophotocatalytic oxidation with maximum COD reduction as 98.36 % for the case of TiO2 was found as best approach compared to sonocatalysis and photocatalysis. The sonophotocatalytic oxidation followed pseudo first-order kinetics for all the catalysts. Overall, the sonophotocatalytic combination involving TiO2 has been demonstrated as the most effective approach for COD reduction of commercial flonicamid solution.