Preparation Of Titanium-based Rare Earth Doped Oxide Coated Electrode And Electrocatalytic Oxidation Of Antibiotic-containing Wastewater

Over-reliance on antibiotics inevitably leads to the abuse of antibiotics,and excess antibiotic drugs will be discharged into the water environment in the form of raw drugs or metabolites,causing pollution of the water environment.Electrocatalytic oxidation technology is an advanced oxidation process that can completely oxidize refractory organic pollutants,and it has excellent environmental friendliness,ease of operation,and high efficiency.The key to electrocatalytic oxidation technology is the electrode materials.Ti/SnO2-based electrodes are promising but still suffer from short lifetimes and low catalytic activity.This study prepared two rare earth-doped electrode materials(Ti/SnO2-Sb-La and coral-shaped Ti/SnO2-Sb-Yb)based on SnO2-coated electrodes using a solvothermal method.The physical properties of the electrodes were characterized by SEM,XRD,and XPS.The electrochemical properties and electrocatalytic activity of the electrodes were characterized using various electrochemical testing methods.The electrocatalytic oxidation treatment of norfloxacin-containing and sulfamethoxazole-containing simulated wastewater was carried out by preparing electrodes,and the electrocatalytic oxidative degradation effect and oxidative degradation mechanism of organic matter were studied respectively.The main research progress is as follows:(1)Uniformly distributed rare earth elements(La or Yb)and Sb co-doped Ti/SnO2 coated electrodes were synthesized via solvothermal method.SEM showed that the two-step solvothermal method could create a more three-dimensional coral-like structure on the surface of the electrode,increased the electrode surface area and provided the possibility of more active sites.When La or Yb was added as a co-dopant,the particle size on the electrode surface was reduced and the proportion of(101)crystal planes increased,enhancing the proportion of adsorbed oxygen(Oad)in SnO2 crystals significantly,generating more oxygen vacancies and thereby increased the electrocatalytic activity and conductivity of the prepared electrodes.(2)The optimal addition ratio of the rare earth element La is Sn:La=100:7.5.Compared with the La 0%electrode,the oxygen evolution overpotential of the La 7.5%increased from 1.91 V to 2.19 V,and the Cdl increased from 1.35 mF/cm2 to 1.93 mF/cm2.In addition,La 7.5%can significantly improve the accelerated lifespan of the electrode,which is 2.3 times that of La 0%.Under the current density of 10 mA/cm2,the electrode lifespan was increased from 145 h to 335 h.The best ratio of rare earth element Yb is Sn:Yb=100:7.5.The Cdl of the Yb 7.5%doped electrode is increased by 16 times compared with Yb 0%,from 0.78 mF/cm2 to 12.58 mF/cm2.Compared with Yb 0%,the accelerated lifetime of Yb 7.5%was significantly improved,about 2.7 times,from 609 h to 1647 h at 10 mA/cm2.(3)By investigating the electrocatalytic oxidative experiment of antibiotic simulated wastewater of the prepared electrodes,it was found that rare earth doping had increase the electrocatalytic activity of Ti/SnO2-coated electrodes significantly,and the degradation followed a quasi-first-order kinetic process.Compared with La 0%,the degradation kinetic value of norfloxacin by La 7.5%increased from 0.0112 to 0.0261(about 2.2 times),and compared with Yb 0%,the kinetic constant value of sulfamethoxazole degradation by Yb 7.5%increased from 0.0114 to 0.0278(about 2.4 times),and increasing the current could significantly improve the degradation effect of sulfamethoxazole.(4)The LC-MS showed the partial degradation intermediate products of simulated wastewater,preliminarily revealed the possible electrochemical oxidative degradation path and reaction mechanism of the model pollutants,and further verified that the model pollutants could be electrocatalyzed oxidative degradation and efficient removal by preparing electrodes.Norfloxacin has three degradation pathways,mainly through the attack on the piperazine group and quinone moiety degradation into some smaller organic molecules or inorganic species,and then achieve complete mineralization of organic matter.Sulfamethoxazole is mainly degraded by hydroxylation reactions,produced by breaking the carbon-sulfur bond formed by the benzene ring with sulfur,which exhibits relatively weak bonding energy and is very susceptible to electrophilic groups(e.g.,·OH),sulfamoxazole degradation triggered by hydroxyl substitution reaction is the main degradation reaction.The results indicate that the novel Ti-based SnO2 coating electrodes doped with rare earth elements La and Yb synthesized by the solvothermal method exhibit good electrocatalytic activity and high stability,which is expected to provide a new and effective means for the oxidative degradation and efficient removal of refractory organic compounds in high-salt wastewater and provide technical support for the efficient removal of antibiotics in the aquatic environment.