Hydrogen peroxide enhanced sonophotocatalytic degradation of acid orange 7 in aqueous solution: optimization by Box-Behnken design

BACKGROUND Sonophotocatalysis has gained great attention for research into practical applications to treat refractory organic dye from wastewater. However, its degradation efficiency needs to be improved further. To further enhance the sonophotocatalytic performance, here we report a novel hydrogen peroxide (H2O2)-assisted titania (TiO2)-based sonophotocatalyic system (H2O2-US-UV/TiO2) for degradation of acid orange 7 (AO7). RESULTS Effects of operating parameters including catalyst dosage, concentration of the oxidative agents and initial pH were analyzed through a response surface method coupled with Box-Behnken experimental design (RSM-BBD) and experiments. Introducing H2O2 into the US-UV/TiO2 system can significantly enhance AO7 removal. A quadratic model was proposed for predicting AO7 degradation using the RSM-BBD method, and the statistical significance of the model was confirmed by ANOVA. The real AO7 removal efficiency (95.8%) under experimental conditions of 0.5 g L-1 TiO2, 4 mmol L-1 H2O2, and initial pH 3 was comparable with the predicated value (98.6%) obtained from this model. Quenching tests revealed that the hydroxyl radical (OH) was the key reactive species in the sonophotocatalytic system. Degradation products including 2-naphthol, 4-carboxylphenylglycine, cinnamic acid and 1,10-Decanediol were identified. CONCLUSION Adding H2O2 improved the degradation performance of AO7 in the US-UV/TiO2 system; H2O2 concentration was a more significant experimental factor than initial pH and TiO2 dosage. A degradation pathway of AO7 removal was suggested according to results of liquid chromatography-mass spectrometry. The novel hybrid H2O2-US-UV/TiO2 system can be utilized as an efficient process for recalcitrant dye wastewater treatment. (c) 2021 Society of Chemical Industry (SCI).