Dual-reaction-center engineering in Cu/CoFe2O4 spinel for pH-universal Fenton reaction toward efficient ofloxacin degradation

This study introduces Cu into the CoFe 2 O 4 structure via a one-step hydrothermal method, creating a polymetallic (Cu/CoFe 2 O 4 ) catalyst with synergistic dual reaction centers. Material characterization reveals that Cu incorporation facilitates the formation and maintenance of low-valent Cu + and Fe 2+ species. Synergistic Cu + /Cu 2+ and Co 2+ /Co 3+ redox couples efficiently shuttle electrons, facilitating the rapid reduction of Fe 3+ (the rate-limiting step) and boosting H 2 O 2 activation efficiency across a wide pH range. The optimized Fenton system achieved complete ofloxacin (OFX) removal within 120 min and high mineralization under neutral conditions (pH 7), exhibiting a reaction rate 19 times higher than pristine CoFe 2 O 4 . The surface-bound •OH was identified as the primary reactive species (56 % contribution) and O 2 •− as secondary contributors. During the reaction, the •OH concentration reached 411 μM within the initial 5 min followed by slower accumulation, with the secondary reaction rate constant between •OH and OFX to be 1.55 × 10 10  M −1 ·s −1 . The O 2 •− generation rate was 1.81 × 10 −8  M·s −1 , and the secondary reaction rate constant between O 2 •− and OFX was 1.08 × 10 7  M −1 ·s −1 . The dominance of surface-bound •OH provides intrinsic tolerance to bulk solution pH fluctuations, explaining the system's high efficiency at neutrality. The material maintained over 95 % efficiency in continuous-flow pilot operation over 75 h, demonstrating exceptional potential for industrial implementation. Toxicity assessment via seed germination and theoretical calculation indicated reduced ecotoxicity of treated effluent. These findings highlight the material's broad pH adaptability, practical efficacy in complex water matrices, and potential for antibiotic wastewater remediation.