Interfacial Synergy in MgO-CeO2/Biochar Enables Superoxide-Driven Catalytic Ozonation of Tetracycline

Abstract

Heterogeneous catalytic ozonation is an innovative approach for the removal of organic pollutants during water purification. However, the mechanism is not yet well understood. In this study, a MgO-CeO₂/biochar composite catalyst was synthesized, and the capability of MgO-CeO₂/biochar for tetracycline hydrochloride ozonation was tested. After 60 min of reaction, the O₃ + MgO–CeO₂/biochar system reached a TCH degradation efficiency of 85.4%, which was significantly higher than the efficiencies of the single-component catalysts MgO/biochar (24.77%) and CeO₂/biochar (28.57%). The performance of the catalysts were observed using the nonlinear fit analysis of the kinetics study, and it appeared that the rate of MgO-CeO₂/biochar increased quite significantly. Regarding the structure, homogeneous dispersion of MgO and CeO₂ nanoparticles, as well as the direct interface between these nanoparticles and the porous biochar support, were achieved, leading to the improvement of ozone adsorption and activation. Oxygen vacancies of CeO₂ and surface basic sites of MgO were found to accelerate the ozone decomposition to reactive oxygen species. Spectral analysis and free radical quenching experiments confirmed that •O₂⁻ attack is the dominant pathway. The stability of the catalyst was exhibited by remaining 81.3% of its original value after four cycles. Also, the catalyst showed its high process efficiency within the pH range of 5 to 10. These findings not only demonstrate that composites with comparable physicochemical properties and wastewater decontamination efficiency can be further integrated with other materials in practical treatment processes.