Bimetallic coupling in dual oxidant centres for the efficient removal of pharmaceuticals from wastewater: insights into the reaction mechanism.

The widespread occurrence of pharmaceutical contaminants such as carbamazepine (CBZ) and norfloxacin (NFC) in aquatic ecosystems poses significant ecological hazards due to their persistence and bioactivity. The current study synthesizes novel bimetallic coupling Ce/Pd/ZY for the efficient degradation of pharmaceuticals using the photo-Fenton-like activation of H2O2 and persulfate (PS) under visible light irradiation. The catalyst exhibits a cubical structure with high crystallinity with a surface area of 36.04 m2 g-1 and average particle size of 8.6 nm, while optical and electrochemical characterization confirmed successful incorporation of nano Ce and Pd, enhanced light absorption, reduced band-gap energy (E g: 2.07 eV), and efficient photocurrent response, promoting efficient redox cycling between Ce3+/Ce4+ and Pd0/Pd2+. The synergistic activation of H2O2 and PS generated reactive oxygen species, predominantly ˙OH and SO4˙- radicals, enabling rapid degradation of CBZ and NFC at neutral pH, achieving 86% and 96%, respectively. The degradation kinetics followed a pseudo-first-order model, showing that radical-driven oxidation is the rate-determining step. Intermediate identification suggested a successive hydroxylation, ring opening, defluorination, and progressive mineralization of pharmaceuticals. Acute toxicity assessment showed a high EC50 for the catalyst and a significant reduction in ecotoxicological risk after treatment of the EPs, confirming the catalyst's safety and the effective detoxification of the transformation products. The results highlight the potential of the Ce/Pd/ZY catalyst as a robust and sustainable catalyst for the advanced treatment of pharmaceutical-contaminated wastewater.