Cobalt-zinc nanoferrite for synergistic photocatalytic and peroxymonosulfate-assisted degradation of sulfosalicylic acid

This work focuses on enhancing the photocatalytic activity of Co1-xZnxFe2O4 (cobalt-zinc nanoferrite) via peroxymonosulfate (PMS) activation for high-performance sulfosalicylic acid (SSA) degradation. The optimal Co0.7Zn0.3Fe2O4 (C2) sample led to the best photocatalytic performance for PMS activation under visible light. The photoluminescence and electrochemical impedance measurements confirmed the higher charge separation for C2 catalyst. The radical quenching and ESR tests revealed that SO4-center dot and center dot OH radicals were the dominant reactive species with little contribution from singlet oxygen for SSA degradation. The presence of Fe3+/Fe2+ and Co3+/Co-2+ redox cycles enhanced the PMS activation to a great extent. Interestingly, the hydroxyl radicals were generated via the PMS activation route and contributed to degradation. As a result, photocatalysis and PMS activation complemented one another and improved performance. The best catalyst was also tested for the photocatalytic activity coupled with PMS activation for other pollutants including bisphenol A, tetracycline, rhodamine B, and 2,4-dichlorophenol. Additionally, due to their strong ferromagnetism and stability, the ferrites can be readily isolated magnetically from treated waste water, indicating their potential application in large-scale wastewater treatment for various contaminants.