Abstract The performance of novel hybrid advanced oxidation, ozone-sono-Fenton process in degradation of acid orange 7 (AO7), as a model of azo dyes was modelled and optimized using response surface methodology (RSM) based on central composite design (CCD). Utilizing a bubbling reactor equipped with an ultrasound probe and in the presence of Fenton reagents, a promising hybrid homogeneous AOP, ozone-sono-Fenton, was investigated. According to the experimental results, the variation trend of degradation efficiency (DE%) with pH, reaction time and Fe2+/ H2O2 molar ratio was modelled with the reduced quadratic model. Additionally, the suitability of the model was indicated with close to unity regression coefficient R2 = 0.9976, R2 adj = 0.9955 . Furthermore, the comparative study of degradation efficiency and COD removal for the individual methods including ozonation, sonication and Fenton reagents as well as their hybrid processes reveals that the novel proposed technique, ozone-sono-Fenton process, is able to rapid and complete degradation of acid orange 7 with initial concentration of 300 mg L− 1, 100% in only 12 min. The complete degradation was obtained under optimum conditions such as pH = 6, reaction time = 12 min and Fe2+/ H2O2 molar ratio = 0.0040. The kinetics evaluation of the acid orange 7 concentration during the processing implied the first-order reaction. Considering the synergetic effect and cost-effectiveness of the hybrid method, the promising ozone-sono-Fenton method could effectively degrade using a wide range of organic contaminants.
