Visible-light-driven peroxymonosulfate activation by robust TiO2-base nanoparticles for efficient removal of sulfamethoxazole

In this study, a novel bimetallic Co-Mo-TiO2 nanomaterial was fabricated through a simple two-step method, and applied as photocatalyst to activate peroxymonosulfate (PMS) with high efficiency for sulfamethoxazole (SMX) removal under visible light. Nearly 100% of SMX was degraded within 30 min in Vis/Co-Mo-TiO2/PMS system, and its kinetic reaction rate constant (0.099 min-1) was 24.8 times higher compare with the Vis/TiO2/PMS system (0.014 min-1). Moreover, the quenching experiments and the electronic spin resonance analysis results confirmed that both 1O2 and SO4•- were the dominant active species in the optimal system, and the redox cycles of Co3+/Co2+ and Mo6+/Mo4+ promoted the generation of the radicals during the PMS activation process. Additionally, the Vis/Co-Mo-TiO2/PMS system exhibited a wide working pH range, superior catalytic performance toward different pollutants and excellent stability with 92.8% SMX removal capacity retention after three consecutive cycles. The result of density functional theory (DFT) suggested that Co-Mo-TiO2 exhibited a high affinity for PMS adsorption, as indicated by the length O-O bond from PMS and the Eads of the catalysts. Finally, the possible degradation pathway of SMX in optimal system was proposed through intermediate identification and DFT calculation, and a toxicity assessment of the by-products was also conducted.