Catalytic ozonation of sulfamethoxazole using loaded CuOx/MgO-SiO2 silica aerogel catalyst: Performance, mechanisms and toxicity

Abstract

Catalytic ozonation technology can quickly and inexpensively treat antibiotic wastewater, where the performance of catalysts determines the level of catalytic efficiency. In this study, CuO_x/MgO-SiO₂ (represented by CuMgSiO) catalysts were prepared using hydrothermal method. Their structure and properties were analyzed by X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS) and automatic specific surface area analyzer. The effects of O₃ concentration, catalyst dosage and initial pH on the degradation of Sulfamethoxazole (SMX) were investigated. Catalytic ozonation mechanisms and degradation pathways of the pollutants were revealed by quenching experiments and liquid chromatography-mass spectrometry analysis. The toxicity of SMX and its intermediates was analyzed by ECOSAR software. The results showed that CuO_x/MgO was successfully loaded onto SiO₂ aerogel and the catalyst exhibited a porous network structure. The highest removal efficiency of SMX reached 87.92% and K_obs was 0.07045 min⁻¹ under the optimum conditions, which was 35.9% and 2.77 times higher than those of ozonation alone. The ·OH, ·O₂⁻ and ¹O₂ were active species for the degradation of SMX, and ¹O₂ played a dominant role. Valence cycling between Cu²⁺/Cu⁺ and Mg²⁺/Mg and adsorption of O₃ by surface hydroxyl groups were key steps in catalytic ozonation, and the toxicity of wastewater after treatment was greatly reduced. This study not only provides an economically feasible catalyst, but also offers a new perspective in the field of antibiotic wastewater treatment.