The Study On The Degradation Of Quinolones By Dielectric Barrier Discharge Non-thermal Plasma

Antibiotics have been used in the prophylaxis and treatment of human and animal diseases since their discovery,and have made great contributions to protect human health and promote economic and social development.In recent years,the globally excessive use of antibiotics has caused a large amount of antibiotic residues in the water environment,which will have a huge impact on the aquatic plants,zooplankton,microorganisms,etc.The pollution of antibiotics to the water environment will cause the development of antibiotic resistance in bacteria and endanger people's health,so the treatment of antibiotic pollution has become the focus of people's attention.Norfloxacin(NOR)and gatifloxacin(GAT)are quinolone antibiotics that were used in large amounts and were widely retained in the water environment.Quinolone antibiotics are stable in nature and have bactericidal and bacteriostatic properties,so traditional treatment methods can no longer meet the degradation of quinolone antibiotic-containing wastewater,and there is an urgent need for an efficient,convenient and green treatment technology.Dielectric Barrier Discharge Non-thermal Plasma(DBD)is widely used in the removal of refractory pollutants because of its high-energy electron radiation,ultraviolet photolysis,ozone oxidation,and free radical oxidation.Titanium dioxide(TiO2)is an excellent photocatalyst.Co-doping graphene and Ho can significantly improve the photocatalytic performance of titanium dioxide.In this study,NOR and GAT were selected as representatives of quinolone antibiotics.DBD combined with graphene and Ho co-doped TiO2 catalyst was used to degrade NOR and GAT together.The sol-gel method can prepare catalytic ceramic plates loaded with Ho and graphene co-doped TiO2 catalyst films in batches.The catalytic ceramic plates have good stability and reusability.XRD,SEM,EDS,DRS,FTIR,BET were used for characterization of catalytic ceramic plates.The analysis results showed that the doping of graphene and Ho could increase the specific surface area of titanium dioxide,reduce the band gap energy,improve the utilization of light energy,and enhance the photocatalytic performance of TiO2.Combining the degradation efficiency and energy yield of norfloxacin with catalytic doped ceramic plates of different doping ratios,1.0 wt%Ho-0.2 wt%rGO-TiO2 was finally determined as the best doping ratio within the scope of this study.On this basis,the Ho-rGO-TiO2-DBD system was used to explore the experimental conditions which could affect the degradation of quinolone antibiotics(NOR,GAT)such as initial concentration,DBD input power,initial pH,initial electrical conductivity,metal ion content in solution,hydrogen peroxide content and COD.Analyze the reason why different experimental conditions affect the degradation efficiency,and determine the ideal experimental conditions.The results showed that the increase of initial concentration and initial conductivity within a certain range could lead to a decrease in degradation efficiency.The input power had an optimal range.After exceeding the optimal range,the system discharge became unstable,and the degradation efficiency would decrease as the power increases.Alkaline conditions are conducive to the system to produce·OH and improve the degradation efficiency.Appropriate amounts of Fe2+and Cu2+ can act as catalysts to increase the reaction rate.Proper addition of hydrogen peroxide can promote the formation of.OH.The increase of COD will inhibit the reaction.Isopropyl alcohol,p-benzoquinone,and ammonium oxalate were used to quench the three active substances·OH,·O2-,and h+,respectively.The results showed that·OH,·O2-,and h+all participated in the oxidative degradation of quinolone antibiotics in the Ho-rGO-TiO2-DBD system.In addition,other active substances(O3,H2O2)oxidation,high-energy electron radiation and ultraviolet photolysis also participate in the degradation.The yields of O3 and H2O2 during the operation of single DBD system and Ho-rGO-TiO2-DBD system were studied.The results showed that the catalyst film formed by Ho and graphene co-doped with TiO2 in the Ho-rGO-TiO2-DBD system could significantly improve the yield of O3 and H2O2 in the system,and O3 and H2O2 have an important role in the generation of free radicals.The intermediate products generated during the degradation of norfloxacin were analyzed by HPLC-MS.Based on the determination of eight intermediate products,the degradation path of NOR by Ho-rGO-TiO2-DBD system was predicted.Finally,it is pointed out that as the reaction progresses,part of these intermediates would eventually be oxidized into small inorganic substances.The results of this paper show that the Ho-rGO-TiO2-DBD system can efficiently degrade quinolone antibiotics,and can further enrich the theoretical knowledge of dielectric barrier discharge low temperature plasma treatment of wastewater.At the same time,the research in this paper can provide some theoretical guidance for the treatment of antibiotic wastewater with dielectric barrier discharge low temperature plasma technology,and some technical guidance for the treatment of antibiotic wastewater.