Low-Temperature Synthesized Mixed-Phase Copper Oxides Deposited for Photocatalytic Antibiotic Degradation

The persistence of antibiotics like ciprofloxacin (CIP) in aquatic environments necessitates the development of efficient, low-cost wastewater treatment technologies. This study investigates a low-temperature fabrication strategy for mixed-phase copper oxide (CuO/Cu2O) coatings synthesized via co-precipitation and immobilized using electrophoretic deposition (EPD). A critical finding was that a 25 min precursor aging time (T25) preserved a metastable mixture of CuO and Cu2O phases, which is highly advantageous for creating heterojunction interfaces that enhance charge separation. In contrast, extended aging (T35) promoted phase consolidation toward bulk CuO, reducing catalytic surface area. During the EPD process, applied voltage acted as an influence to the relative phase composition and deposition behavior of the deposited coatings; 1.0 V was identified as the optimal condition, balancing high phase fidelity with enhanced crystallinity (average crystallite size of 30.6 nm) and mechanical stability. Photocatalytic experiments demonstrated significant CIP degradation, with the 0.9 V and 1.0 V films outperforming the 1.2 V film, possibly due to more favorable surface chemistry and phase diversity. While the 0.9 V film achieved the highest mineralization efficiency (18% TOC removal), the 1.0 V film offered the best balance between photocatalytic activity, structural stability, and phase selectivity for practical applications. High-Performance Liquid Chromatography-Mass Spectrometry HPLC-MS analysis suggested that degradation proceeds through oxidative pathways involving piperazine ring cleavage and defluorination.