Ozone-Activated Degradation of Phenol Over CoAl2O4/γ-Al2O3: Identifying Active Sites and Radical-Mediated Mechanisms

To address the challenges posed by highly toxic and recalcitrant compounds in phenol-containing wastewater, a novel CoAl2O4/γ-Al2O3 catalyst was synthesized via an impregnation-calcination method and applied for catalytic ozonation of phenolic wastewater. The catalyst was thoroughly characterized using X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area analysis, Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma (ICP) analysis. The catalyst’s abundant Lewis acid sites act as active centers, promoting the decomposition of ozone into reactive oxygen species. This study elucidates the pathways by which the CoAl2O4/γ-Al2O3 catalyst synergistically activates O3 to generate O2·−, ·OH, and 1O2, revealing that phenol mineralization primarily proceeds through ·OH and 1O2-mediated oxidation. Compared to ozonation alone, the CoAl2O4/γ-Al2O3 catalyst demonstrates superior O3 activation capability, significantly enhancing the phenol mineralization efficiency from 13.5% to 56.5% while improving ozone utilization (mgTOCremoved/mgO3consumed) from 0.02 to 0.08. Remarkably, the catalyst maintains excellent stability over multiple reaction cycles. Toxicity evaluation confirms substantial reduction in biotoxicity of the treated wastewater. These findings collectively demonstrate that CoAl2O4/γ-Al2O3-based catalytic ozonation represents an efficient and promising technology for phenolic wastewater treatment.