Modeling and optimization of the photocatalytic degradation of Tartrazine in aqueous solution

The application of heterogeneous photocatalysis process using ZnO photocatalyst for the degradation of Tartrazine (TRZ) dye in aqueous solution was investigated in a batch reactor. The estimation, the comparison of the parameter?s effects and the optimization of the removal yield of TRZ were realized by using Box-Behnken experimental design (BBD). The results suggested that the most influential factor on the photocatalytic degradation of the dye was the initial TZR concentration with an effect of (-23.24), the second in the order was the amount of the catalyst with an effect of (+18.09), the third was the reaction time with an effect of (+15.38) and the fourth was stirring speed with a positive effect of (+4.41). The model obtained by BBD led to the following optimal conditions for degradation yield of TRZ: initial concentration of TZR equal to 20.035 mg/L, reaction time equal to 88.635 min, 0.6409 mg/L of ZnO amount and 404.9 rpm for the stirring speed, which gave 98.576% of degradation efficiency. The study of irradiation type effect shows that a solar irradiation gave higher yield than photocatalysis by UV lamp. The O2?- radicals were the principal active species responsible of the degradation of TRZ. The BOD5/COD ratio increased from 0.26 to 0.41 after 60 minutes of photocatalysis under solar light, indicating the feasibility of coupling the photocatalysis process to biological treatment for the removal of TRZ.