Highly efficient degradation of moxifloxacin through heterogeneous activation of peroxymonosulfate using Co₃O₄-g-C₃N₄ composites: Optimization of interfering factors

The disastrous pollution resulting from antibiotics may traverse extensive distances through water, presenting a serious threat to aquatic ecosystems and human well-being. The catalyst-assisted heterogeneous activation of peroxymonosulfate (PMS) has emerged as an intriguing technology for purifying such wastewater. Herein, we have designed cobalt tetroxide anchored over graphitic carbon nitride (Co₃O₄-g-C₃N₄) catalysts through an impregnation and high-temperature calcination technique for the effective degradation of moxifloxacin (MOX) antibiotics from wastewater. The experiments revealed that the MOX degraded completely in 21 min in the Co₃O₄-g-C₃N₄/PMS system with a degradation kinetics constant of 0.1858 min⁻¹, faster than the Co₃O₄/PMS under optimal conditions ([Co₃O₄-g-C₃N₄] = 0.5 g/L, [PMS] = 0.5 mM, [MOX] = 20 mg/L, pH = 6.3). Specifically, the higher degradation of MOX in the Co₃O₄-g-C₃N₄/PMS system can be credited to the larger surface area (97.22 m²/g) of the Co₃O₄-g-C₃N₄ catalyst in comparison to the Co₃O₄ (69.08 m²/g), which enhanced the accessibility of catalytic active sites and improved the PMS activating process. Further, the impression of varied operating factors and intervening anions on MOX abatement was also scrutinized. The production of reactive oxygen species was verified using quenching experiments and further validated by electron paramagnetic resonance analysis. The mechanistic degradation pathways of MOX were anticipated through the acquisition of degradation by-products. The mechanistic insight revealed that the PMS activation was caused by the transitions of Co³⁺/Co²⁺ pairs in the reaction system. Overall, this study sheds new insights for subsequent research into the catalytic mechanism of heterogeneous catalysts utilizing PMS activation to degrade organic pollutants.