Ozone Catalytic Oxidation for Treating Polyethylene Glycol-400 in Photovoltaic Wastewater

Polyethylene glycol-400 (PEG-400), a critical lubricant in photovoltaic silicon wafer slicing, is highly recalcitrant to biodegradation and environmentally persistent. Direct discharge of PEG-400 not only induces water eutrophication and disrupts aquatic ecosystems but also poses chronic health risks to humans through long-term environmental accumulation and water contamination. However, conventional wastewater treatment technologies exhibit limited efficiency in removing PEG-400. In this study, the degradation of PEG-400 was systematically investigated using an O 3  + H 2 O 2  + Mn-Cu/γ-Al 2 O 3 catalytic oxidation process. Single-factor experiments combined with response surface methodology were employed to optimize the catalyst preparation and reaction parameters. Finally, the degradation mechanism and pathway are revealed. The results showed that the Mn-Cu/γ-Al 2 O 3 catalyst prepared under the conditions of 0.1 mol/L impregnation concentration, 500℃ calcination temperature, and 2 h calcination time achieved the optimal catalytic activity. Under the optimal conditions of O 3 concentration of 60 mg/L, H 2 O 2 dosage of 1.8 mmol/L, catalyst dosage of 4 g/L, gas flow rate of 400 mL/min, and reaction time of 90 min, the removal rate of PEG-400 reached 100%, with COD and TOC removal rates of 76.3% and 53.76%, respectively. Radical quenching experiments confirmed that ·OH, ·O 2 − and 1 O 2 were the dominant reactive oxygen species. FTIR and GC–MS analysis revealed that PEG-400 degraded via ether bond cleavage into intermediate products (e.g., aldehydes, carboxylic acids), which verified non-toxicity by T.E.S.T software, and ultimately mineralized into CO 2 and H 2 O.