Efficiency of photocatalytic ozonation process in the presence of CoFe₂O₄/ZnTiO₃/Ag nanocomposite for the removal of bisphenol a from aqueous solutions

Bisphenol A (BPA), a ubiquitous endocrine-disrupting compound, persists in aquatic environments and resists conventional wastewater treatment, posing ecological and human health risks. In this study, a magnetic CoFe₂O₄/ZnTiO₃/Ag ternary nanocomposite was prepared by co-precipitation and calcination and tested as a heterogeneous catalyst for BPA removal by photocatalytic ozonation (6 W UV-C lamp, 0.2 g/h ozone) in a model aqueous system. XRD showed reflections of a spinel phase and metallic silver together with weak reflections attributed to ilmenite-type ZnTiO₃; however, the iron-rich EDX composition and an XRD pattern of the calcined core that includes reflections consistent with hematite show that the material is not phase-pure. Batch experiments (one run per condition) varied initial BPA concentration (10–50 mg/L), catalyst dosage (0.25–0.75 g/L), pH (4–10) and reaction time (up to 240 min). Under the best conditions tested (pH 7, 0.5 g/L catalyst, 10 mg/L BPA), BPA removal reached 91.30% and COD removal 82.5% after 240 min. Under the same conditions, removal was 76.09% for UV-C/O₃, 70.65% for O₃ alone, 9.78% for UV-C alone and 1.09% for the catalyst alone. The catalyst with UV-C but without ozone removed 85.87%, and the catalyst with ozone but without light removed 80.43%, so the composite acted both as a photocatalyst and as an ozonation catalyst. A 400 W metal halide lamp used as a simulated-sunlight source gave no improvement over the catalyst/O₃ system (80.65% versus 80.43%). The apparent rate constant of the three-component process was about 1.8 times the sum of those of the single processes but only about 1.25 times that of the best two-component process (catalyst/UV-C). Removal fell from 91.30% to 47.83% over seven reuse cycles, while the catalyst was easily recovered with a magnet. The proposed mechanism and degradation pathway are hypotheses based on the literature and on tentatively identified intermediates and were not tested directly. The results suggest that the system is a promising option for BPA removal in model water; regeneration, metal leaching, toxicity of the treated water and performance in real wastewater remain to be studied.