Catalytic ozonation of coal chemical biochemical secondary effluent by a Cu-MnFe₂O₄/Bt ozone catalyst

In this study, a Cu-MnFe₂O₄/Bt ozone catalyst was synthesized using bentonite (Bt) as a carrier and characterized through scanning electron microscopy, X-ray diffraction, Fourier transform infrared, BET, X-ray photoelectron spectroscopy, and vibrating sample magnetometry. Then, the effects of reaction time, pH, ozone dosage, catalyst dosage, and reactor height-to-diameter ratio on chemical oxygen demand (COD) and hydroquinone removal were investigated in simulated wastewater. The effects of these parameters on COD removal in actual biochemical secondary effluent produced by coal chemical processing, and the stability of the catalyst and catalytic ozonation mechanism were analyzed. Furthermore, a critical weight–coupled coordination degree comprehensive model (CWCCDC Model) was developed to evaluate the catalytic ozonation system. Results demonstrated that the Cu-MnFe₂O₄/Bt catalytic ozonation system outperformed the blank Bt catalytic ozonation and the ozone alone ozonation systems in hydroquinone removal. Under optimal conditions, that is, reaction time of 60 min, pH of 9, ozone dosage of 400 mg/L/h, catalyst dosage of 0.3 g/L, and reactor height-to-diameter ratio of 10:1, the Cu-MnFe₂O₄/Bt ozone catalyst achieved 70.85 % COD removal rate for coal chemical biochemical secondary effluent. Radical quenching experiments revealed that hydroxyl radical oxidation was the dominant pathway in the Cu-MnFe₂O₄/Bt catalytic ozonation system, which followed first-order kinetic law. The catalytic ozonation effectively oxidized and degraded phenols, polycyclic aromatic hydrocarbons, and other macromolecular organic compounds in the coal chemical biochemical secondary effluent.