OPTIMIZATION OF ALACHLOR DEGRADATION ON S-DOPED TiO2 BY SONOPHOTOCATALYTIC ACTIVITY UNDER VISIBLE LIGHT

Experimental design was employed to identify the optimum operating conditions for sonophotocatalytic degradation of alachlor using S-doped TiO2 under visible light. A response surface methodology based on the Box-Behnken design was used. Three operational variables of alachlor degradation were investigated: the initial alachlor concentration, catalyst loading, and ultrasonic power intensity. Sonophotocatalysis, the combination of photocatalysis and sonolysis, was employed on the widely used herbicide alachlor in an aqueous solution with S-doped TiO2 under a wide range of visible light. The sonophotocatalytic degradation of alachlor was statistically investigated. The experimental design model predicted a quadratic model as a function of the relationship between the alachlor removal efficiency and the independent variables. The correlation coefficient (R-2) between the experimental data and model data was 0.98. The obtained optimum operating conditions for achieving 85% alachlor removal were an alachlor concentration of 1 mg L-1, a catalyst loading of 1.785 g L-1, and an ultrasonic power intensity of 0.55 W mL(-1) (44 W in 80 mL). In addition, the model results proposed that ultrasonic power increased the alachlor removal efficiency. It may be concluded that response surface methodology based on the Box-Behnken design can be a precise and reliable technique for optimizing the operating conditions of alachlor degradation using sonophotcatalytic activities.