Photoelectrocatalytic Degradation Of Fluoroquinolone Antibiotics In Water

Fluoroquinolones antibiotics?FQs?are one of the most widely used antibiotics.In recent years,FQs have been widely detected in water environment.The residual problems and potential hazards of FQs have aroused people's attention.The removal efficiency of FQs in the traditional water treatment technology is not ideal.Photocatalytic technology,as an advanced oxidation technology,can effectively remove refractory organic compounds in the water environment.The carrier recombination rate of photocatalyst is high and the catalyst powder is difficult to reuse.In order to solve these problems,the titanium dioxide nanotube photocathode was prepared by anodic oxidation method and the preparation conditions were optimized.The self-doped TiO₂ nanotube photocathode was modified by electrochemical reduction method and characterized by SEM,XRD,XPS and electrochemical workstation.Using self-doped TiO₂nanotube as working electrode and norfloxacin as target substrate,the photocatalytic degradation efficiency and kinetics of fluoroquinolones antibiotics in aquatic environment were studied.The main results are as follows:1.Study on the influencing factors of the preparation of TiO₂ nanotube photoelectrodes by anodic oxidation.In the process of preparing TiO₂ nanotube photoelectrode by anodic oxidation,the anodic oxidation voltage,oxidation time,oxidation temperature and calcination temperature all have an effect on the photocatalytic performance of the prepared TiO₂ nanotube.In the scope of this experiment,the higher the anodic oxidation voltage and the longer the oxidation time,the better the photocatalytic performance of the prepared TiO₂ nanotube.The effect of oxidation temperature and calcination temperature on the photocatalytic performance of the TiO₂nanotube has the best value.The photocatalytic performance of the prepared TiO₂ nanotube was the best when the oxidation temperature is 25?and calcination temperature is 550?.2.Preparation and characterization of self-doped TiO₂ nanotube photoelectrode.The self-doping modification of TiO₂ nanotube photoelectrode was carried out by electrochemical reduction.It was found that the photocurrent density of self-doped TiO₂nanotube increased with the increase of reduction time when the reduction time was 0⁶0s.When the reduction time is continued to increase,the photocurrent density does not increase any more.It is speculated that the reason may be that the doping of Ti³⁺has reached saturation.The SEM,XRD,XPS and photoelectrochemical properties of The self-doped TiO₂nanotube photocathode were characterized.It was found that the electrochemical reduction method did not change the morphology and crystal structure of nanotubes.The characterization results of XPS showed that the self-doping of Ti³⁺was successfully realized by electrochemical reduction method.The results show that the self-doping modification greatly improves the conductivity of nanotube photocathodes,and improves the generation,separation and transmission efficiency of photogenerated electron-hole pairs.3.Study on the degradation of norfloxacin in water by self-doping TiO₂ nanotube photoelectrode.The photoelectrocatalytic degradation of norfloxacin follows the Langmuir-Hinshelwood?L-H?pseudo-first-order kinetic model.When the applied bias voltage is 1.2V,the electrolyte concentration is 0.01mol/L and the initial concentration of norfloxacin is 5 mg/L,the degradation rate of Norfloxacin by self-doped TiO₂ nanotube is 92.1%.The apparent rate constant is 0.4986 h^-1,which is 6.05 times of photolysis and 2.40 times of photocatalysis.The result shows that the external bias can effectively promote the separation of carriers and significantly improve the photocatalytic effect of self-doped TiO₂ nanotube photoelectrodes.However,during photoelectrocatalytic degradation,norfloxacin was not fully mineralized.After 5 hours of reaction,the degradation rate of total organic carbon?TOC?was only 39.19%.In the degradation process of norfloxacin,h_v⁺,·OH and·O₂^-all play a certain role,and the contribution to the degradation rate of norfloxacin is in the order of·O₂^-,h_v⁺,OH.The self-doped TiO₂ nanotube photoelectrode has good repeatability and stability,which shows good application potential.After 5 consecutive uses,the photocatalytic degradation rate of norfloxacin decreased by only 0.6%.