Preparation Of BiVO₄-based Photoanode And Its Photocatalytic Coupling With Permonosulfate For Ciprofloxacin Degradation

Antibiotics,as the most important drugs in human drugs and veterinary drugs,have been widely used in the prevention and treatment of human bacterial infections and animal infectious diseases.However,due to their overuse and improper discharge in the past decades,they have been widely distributed in environmental water bodies.Therefore,the removal of refractory antibiotics from environmental water has become a global research topic.Due to the complex composition of antibiotic wastewater,it is difficult to completely remove it by traditional water treatment methods.Compared with traditional technologies,advanced oxidation processes(AOPs)have many advantages in antibiotic degradation and photoelectrocatalysis(PEC)and permonosulfate(PMS)are very effective in antibiotic degradation.Bismuth monoclinic vanadate(BiVO4)is a visible light responsive catalyst,and BiVO4 is non-toxic,eco-friendly and shows good photocatalytic ability.However,its low electron mobility and short carrier diffusion distance limit its photocatalytic activity.Therefore,researchers have proposed different methods to improve the catalytic activity of BiVO4,such as metal and nonmetal doping and preparation of heterostructure composites.In this paper,the photocatalytic performance of BiVO4 was optimized by metal supported(Co)and supported cocatalyst(CoxCO3).By using the modified BiVO4based photoanode material for photocatalytic degradation of ciprofloxacin(CIP)coupled with PMS,it was found that its degradation performance was greatly improved.The research contents of this paper are as follows:(1)Preparation of Co-BiVO4 Photoanode and Its Photocatalytic Coupling Performance of PMS for CIP DegradationBiVO4 semiconductor catalyst was prepared by electrodeposition method.On this basis,Cosupported BiVO4 composites(Co-BiVO4)were prepared by soaking BiVO4 in 0.1 M cobalt nitrate solution for 12 h.The successful supported of Co was proved by XRD,SEM and TEM.The results of Mapping test prove the existence and uniform distribution of Bi,V,O,C and Co.Under xenon lamp irradiation,the photocurrent density of Co-BiVO4 photoanode can reach 7.2 mA/cm2 at 0.5 V(vs.Ag/AgCl)and ciprofloxacin(20 ppm).The photocatalytic degradation of ciprofloxacin on Co-BiVO4 coupled with PMS was studied.The results showed that Co-BiVO4 electrode exhibited better photocatalytic degradation performance than pure BiVO4 electrode.The degradation rate of ciprofloxacin(20 ppm)by Co-BiVO4 photoanode reached 90.14%within 60 min.The cyclic experiment and ICP-OES proves that the material has good stability and reusability.By using free radical trapping experiment,the main active oxygen species in the degradation process were analyzed as SO4·-and h+.(2)Preparation of CoxCO3/BiVO4 Photoanode and Its Photocatalytic Coupling Performance of PMS for CIP DegradationCobalt carbonate(CoxCO3)catalyst is a particularly effective and easy to synthesize co-catalyst The catalyst can improve the performance of BiVO4 photoanode material.CoxCO3 was deposited on the surface of BiVO4 by photoelectric deposition method,and CoxCO3/BiVO4 composites were obtained.SEM and elemental distribution diagram show the close bonding of CoxCO3 film with BiVO4 and the unifom distribution of Bi,V,O,C and Co elements.The degradation rate of ciprofloxacin(20 ppm)on CoxCO3/BiVO4 photoanode was 80.35%in 20 min under xenon lamp irradiation and 0.5 V(vs.Ag/AgCl)in 0.5 M electrolyte solution.The photocurrent density measured by COxCO3/BiVO4 photoanode in ciprofloxacin and PMS solution can reach 7.61 mA/cm2 by LSV.The fluorescence spectra confirmed that the recombination of BiVO4 and CoxCO3 cocatalyst could significantly reduce the recombination of electron-hole pairs.Electrochemical impedance spectroscopy shows that the introduction of PMS can promote the separation and transfer of photo-generated electrons and holes.The possible active species in the degradation process were analyzed by free radical traping and the possible degradation mechanism of ciprofloxacin by CoxCO3/BiVO4 photoelectrocatalysis coupled with PMS was put forward.