Bicarbonate-assisted Co_xS_y/γ-Al₂O₃ Catalyzed Hydrogen Peroxide Degradation Of Cephalosporin Antibiotics

With the progress and development of society,human beings are more and more concerned about their own health,and various health care and medical supplies are used in large quantities,which is followed by more and more serious water pollution problems in China,among which antibiotic wastewater is of great concern to researchers because of the complex water quality components,difficult biodegradation and low concentration.The heterogeneous Fenton technique as a traditional advanced oxidation technique is well studied in the removal of antibiotic pollutants,but in the practical application there are problems such as low oxidation efficiency,narrow p H applicability range and catalyst metal ion precipitation;while the bicarbonate activated hydrogen peroxide technique as a green method is also difficult to be used on a large scale due to the defects of excessive cost and poor oxidation properties.In this study,Co_xS_y/γ-Al₂O₃loaded catalysts were prepared by hydrothermal synthesis,and the bicarbonate-activated hydrogen peroxide system was combined with the heterogeneous Fenton system by introducing bicarbonate to create an alkaline environment for the heterogeneous Fenton system,and the enhanced effect of bicarbonate on the heterogeneous Fenton reaction was investigated,using Cefalexin as a model contaminant to the degradation effect of cephalosporin antibiotics under this system and the reaction mechanism were investigated.The catalysts were prepared with a molar ratio of Co to S of 1:1,a molar ratio of active component to carrier of 1:1,and hydrothermal heating at 180℃for 10 h.The best catalytic effect was achieved at the dosage of 5 m M of HCO₃^-,10 m M of H₂O₂and 0.05 g/L of catalyst,and90.0%of Cefalexin could be removed within 60 min.The characterization results showed that the active components were uniformly immobilized onto the carrier with no significant changes before and after the reaction.The mechanism of bicarbonate enhanced heterogeneous Fenton oxidation was hypothesized by simulations and full-wavelength scans that bicarbonate complexes with Co（III）on the catalyst surface and promotes the conversion of Co（III）/Co（II）redox pairs.In addition,electrochemical analysis was used to verify that the presence of HCO₃^-enhances the electron transfer in the system and promotes the production of active species in the system.The active species that play a role in the system are·OH,¹O₂,O₂^·-and CO₃^·-,among which CO₃^·-occupies a dominant position.The presence of bicarbonate reduces the reaction energy barrier for the conversion of Co（III）to Co（II）,enhances the species of active species in the system,and promotes the adaptation of the system to oxidize pollutants,as confirmed by density functional theory.