The Performance And Mechanisms Of The Degradation Of Cefaclor By The Electro-Fenton Process Using A Novel Ti₄O₇ Anode

In recent years,a variety of environmental problems caused by the production and use of antibiotics have attracted more attention.Antibiotics might enter in the environment in the form of mother or metabolites after use,which will cause serious problems such as bacterial resistance,which may threaten the ecosystem,as well as human health.Antibiotics in water were difficult to be effectively removed by traditional biochemical treatment processes,so it was urgent to develop new technologies.This paper selected the cephalosporin antibiotic Cefaclor（CFC,the second generation of cephalosporin antibiotics）as the target,a novel titanium oxide（Ti₄O₇）as the anode and electrochemical advanced oxidation technology（EAOPs）were used to degrade the CFC.The degradation conditions were optimized,the reaction mechanisms were explored,the degradation products were monitored and the CFC mineralization path was proposed.The following four results were obtained:（1）Effect of anode materials used in the EAOPs on the degradation of CFC:Ru O₂/Ti and Ti₄O₇/Ti were chosen as anodes for comparing the mineralization efficiency of different anodes on CFC in anodic oxidation（AO）,electro-Fenton（EF）and photoelectro-Fenton（PEF）processes.The results showed that the mineralization effect of Ru O₂/Ti anode on CFC was（15.1%）slightly better than that of Ti₄O₇/Ti anode（6.9%）during AO process.However,the mineralization efficiency of Ti₄O₇/Ti anode for CFC was（59.9%and 71.7%,respectively）better than that of Ru O₂/Ti anode（46.8%and 64.3%,respectively）in EF and PEF systems,which indicated Ti₄O₇/Ti anode can enhance the degradation effciency in EF and PEF processes.（2）Reaction mechanisms of different EAOPs using Ti₄O₇/Ti anode:Four systems using Ti₄O₇/Ti anode were compared the production of H₂O₂ and^·OH.The results showed that the production of H₂O₂ in different systems was as follows:AO+Fe²⁺<AO<EF<AO-H₂O₂,and the maximum concentrations were 53.8μm,147.8μm,232.3μm and 2011.9μm,respectively.The production of^·OH in different systems was following:AO<AO-H₂O₂<AO+Fe²⁺<EF,the maximum production were 1.1μm,2.1μm,5.2μm and 20.5μm,respectively.This indicated that ACF cathode can effectively generate H₂O₂,while EF can promote the generation of^·OH.（3）Efficient degradation of CFC by Ti₄O₇/Ti-EF system:Three EAOPs using Ti₄O₇/Ti anode were established and compared.It was found that the degradation efficiency followed:Ti₄O₇/Ti-AO<Ti₄O₇/Ti-AO-H₂O₂<Ti₄O₇/Ti-EF.This indicated that Ti₄O₇/Ti-EF process can degrade CFC effectively.During CFC degradation,the formation of organic acids and inorganic ions were detected.The degradation conditions of Ti₄O₇/Ti-EF prcoess were optimized,and the optimal conditions were as follows:I=0.36 A,p H=3.00,[Fe²⁺]=1.0 m M,[CFC]₀=200 mg·L^-1,and under the optimal conditions the mineralization rate was 59.9%.The generated aromatic byproducts were detected by UPLC-QTOF-MS,and the possible degradation pathways were deduced.（4）The mineralization of CFC by Ti₄O₇/Ti-PEF system:Five EAOPS reaction systems were established using Ti₄O₇/Ti anode.The mineralization efficiency of each system for CFC followed:Ti₄O₇/Ti-AO<Ti₄O₇/Ti-AO-H₂O₂<Ti₄O₇/Ti-UVA-AO-H₂O₂<Ti₄O₇/Ti-EF<Ti₄O₇/Ti-PEF.The results showed that CFC can be efficiently mineralized by Ti₄O₇/Ti-PEF system.During CFC degradation,Oxalic acid,Oxamic acid,Formic acid and Acetic acid were detected,and Formic acid and Acetic acid were the main organic acids.It was also detected NH₄⁺,NO₃^-,Cl^-and Cl O₃^-ions generated in the solutions.The generation of organic acids in Ti₄O₇/Ti-PEF system was much higher,and the generated NH₄⁺concentration was 12.59 mg·L^-1（66.2%of the initial total nitrogen）,the Cl^-concentration was 14.01 mg·L^-1（73.5%of the initial total chlorine）,indicating that PEF can degrade CFC completely.By optimizing the conditions of Ti₄O₇/Ti-PEF process,the optimal conditions were obtained,and the mineralization rate was 71.7%.UPLC-QTOF-MS analysis showed that six aromatic byproducts were produced during CFC degradation,and the possible degradation process was proposed.