Study on the treatment of methyl orange contaminated water by activated carbon fiber/copper oxide as persulfate activator under microwave irradiation

To effectively treat refractory azo dye wastewater, microwave advanced catalytic oxidation technology was adopted to degrade the model pollutant methyl orange using activated carbon fiber (ACF)/CuO as the catalyst and potassium persulfate (K₂S₂O₈) as the oxidant. The optimized experimental parameters and the degradation pathway of methyl orange were determined. The results showed that when the microwave power was 500 W, the irradiation time was 2 min, the dosage of potassium persulfate was 0.6 g/L, and the dosage of ACF/CuO was 10 g/L, the removal rate of methyl orange solution was close to 100%, the COD removal rate was 89.65%, and the TOC removal rate was 72.36%. Mechanism analysis indicated that the double bond was broken to generate acid and p-nitrophenol, which were gradually degraded to benzene and phenol under the oxidation of sulfate radical. Subsequently, the benzene and phenol underwent chain cleavage to form maleic anhydride, and part of the benzene, phenol, and the generated maleic anhydride were ultimately degraded to water and carbon dioxide.