Research On Enhancement Of Reactive Oxygen Species And Degradation Of Sulfadiazine By Micro-Bubble Cathode

China is a big country of antibiotic production and consumption.Due to the lack of strict supervision and unreasonable use for a long time,the problem of antibiotic contamination is serious.The concentration of suspended matter and the content of organic matter in antibiotic wastewater are usually high,and there are a lot of biotoxic and bioinhibitory components.The disorderly disposal of wastewater containing resistance will threaten human health and the growth and metabolism of other organisms in the environment,and stimulate the generation of resistant bacteria.Therefore,how to effectively reduce and remove the residual antibiotics in the environmental system has become a research trend in recent years.Advanced oxidation technology can effectively degrade refractory pollutants by producing·OH,and has the advantages of non-selective oxidation,fast treatment speed and high efficiency,which is more advantageous than traditional biological treatment in the treatment of antibiotic wastewater.Among them,the electro-Fenton method can generate H₂O₂through in-situ 2-electron oxygen reduction reaction and realize iron circulation in the system,which overcomes the shortcomings of the traditional Fenton reactor,such as large sludge volume and high transport risk of H₂O₂.Therefore,it has been widely concerned.Although the Fenton technology presents unique advantages for treating organic pollutants,there are still some core problems.For example,in situ production of H₂O₂speed limit,Fe³⁺reduction at the cathode is blocked,low current efficiency,which restrict the application of electro-Fenton process in practical engineering.Therefore,increasing H₂O₂production,enhancing Fe³⁺reduction and reducing energy consumption have become the main research tasks of electro-Fenton process.In this paper,the effects of rotating system and porous system on the accumulation of H₂O₂and the strengthening mechanism were investigated.Among them,the rotation system mainly promotes the mass transfer of dissolved oxygen and strengthens the2-electron ORR process by weakening the diffusion layer thickness of the cathode/solution thin liquid layer.The results show that at 300 rpm,the H₂O₂accumulation of the tubular titanium base cathode is 558.26μm in 120 min,which is about 71.8%higher than that at 0 rpm.In the porous system,the gas is supplied directly through the porous tubular titanium cathode,which produces micro-bubbles,and improves the concentration of dissolved oxygen in the system,thus strengthening the generation of H₂O₂.The results show that under the condition of 0.02 m³·h^-1,the H₂O₂yield of the porous tubular cathode reaches 627.00μm in 120 min,which is about92.9%higher than that of the conventional system.With the increase of gas flow rate from 0.1m³·h^-1to 0.4 m³·h^-1,the accumulation of H₂O₂increased by 35.2%on the whole.In order to further improve the H₂O₂production,a rotating micro-bubble cathode system was constructed by combining the rotating system with the porous system.It was found that the H₂O₂accumulation in the system reached 1312.32μm in 120 min,which was about four times that of the traditional immersion system.LSV analysis showed that the system had stronger oxygen reduction reaction electrochemical reactivity.In addition,the rotating micro-bubble cathode system also showed better iron reduction capacity,with the reduction rate of Fe³⁺reaching about 60%,much higher than the conventional system（25%）.In the treatment of pollutants,the rotation-microbubble cathode system also showed better degradation ability and iron cycling ability.Under the condition of 50μM Fe²⁺,the degradation rate of sulfadiazine could reach 98.81%after 3 h electrochemical treatment,and the mineralization rate reached 46.7%after 9 h treatment.The unit energy consumption is 0.4526Wh·mg^-1TOC.The degradation pathways of sulfadiazine were preliminarily analyzed,including hydroxylation reaction,S-N bond fracture and S-C bond fracture.The rotating micro-bubble cathode system successfully constructed in this project has a good ability to treat sulfadiazine,and the analysis of response parameters and degradation path provides a theoretical basis for the actual treatment of sulfadiazine antibiotic wastewater.