Synthesis Of Fe₂O₃/g-C₃N₄/N Co-doping TiO₂ Nanotube Arrays And Application In Photocatalytic Degradation Of Endocrine Disrupter Bisphenol A

With the rapid development of industry,many endocrine disrupting chemicals（EDCs）are released into the aqueous environment increasingly through the daily life and productive activity of human.Most EDCs have the characteristics of toxicity,stable structures,which leading to the degradation-resistant.Therefore,they can cause serious problems on the hormonal malfunction of human and animals when they are exposed in the environment.At present,EDCs has been listed as one of the main emerging contaminants（ECs）.In addition,the hazardous EDCs cannot be removed completely by conventional sewage treatment technologies because the limited degradation rate.Hence,it is necessary to develop a novel and effective treatment technology to solve this problem.Advanced photocatalytic oxidation process can be an alternative technology to accomplish this task because it has the advantages of low secondary pollution,high degradation efficiency and the potential of utilizing sunlight as the reaction light source.Photocatalyst plays a key role in the efficiency and practicability of photocatalytic technology.Currently the available photocatalysts which can degrade the organic pollutants in water are mainly the metal oxide semiconductor materials,such as Zn O,Sn O_2,Cd S,Bi VO₄,Fe₂O₃,etc.These photocatalysts all have certain photocatalytic efficiency on organic pollutions degradation.However,they also have the risk of toxicity to human and environment because they all have the risk of dissolution into water.Therefore,at present the nano TiO₂ semiconductor materials are more feasible to be an ideal photocatalyst because their environmental safety peculiarity.However,TiO₂ has no remarkable photocatalytic ability to degrade organic pollutants in water due to the wide band gap and low photoelectric conversion efficiency.In order to improve the catalytic performance of TiO₂,doping,composite and surface modification are usually implemented.In this study,g-C₃N₄ and Fe₂O₃ co-doped modified TiO₂ nanotube arrays photocatalyst（Fe₂O₃/g-C₃N₄@N-TNA）were prepared by multi-element co-doping method.The preparation parameters of synthesizing Fe₂O₃/g-C₃N₄@N-TNA were obtained,and the effect and kinetic mechanism of the photocatalytic degradation of EDCs bisphenol A（BPA）were also studied.The results show that the doping of N can effectively reduce the band gap of TiO₂ and reduce the transition energy.The g-C₃N₄ doping,which has lamellar network structure,can improve the transmission efficiency of photogenerated carriers and improve the efficiency of photocatalysis.Fe₂O₃ doping can further reduce the excitation energy level and lead to the excitation wavelength redshift,thus improving the reaction effect.This study also discussed the mechanism of photodegradation of BPA by multi-element co-doping TiO₂ nanotube arrays.It also enriched the preparation path of photocatalyst,and provided a new idea for the effective treatment of environmental endocrine disruptors.The specific works are as follows:（1）The TiO₂ nanotube array（TNA）photocatalyst was prepared by anodic oxidation method.The morphology and basic characters of TNA was obtained by using X-ray diffractometer（XRD）,field emission scanning electron microscopy（SEM）,solid（FE-SEM）ultraviolet spectrophotometer（UV vis）and Raman（Raman）,X-ray photoelectron spectroscopy（XPS）analysis and the characterization of photoelectric system.Results show that the diameter of TNA is about 50 nanometers.Anatase and rutile type mixed crystal types are found.It has the light absorption ability under the visible light（400 nm to 800 nm）irradiation.The excitation energy of TNA is 3.03 e V.The performance of TNA photocatalytic degradation BPA solution also was studied.The results showed that the optimal conditions of TNA synthesized are as follows:the mass fraction of 0.4%NH₄F and volume fraction of 1%H₂O glycol electrolyte,calcining temperature of 450°C.The TNA which under the optimal synthesized condition has better photocatalytic performance.The 100m L BPA,which the initial concentration was 4 mg/L,removal rate can reach 76.3%under the simulated sunlight（200 nm to 800 nm）irradiation with 10 cm² of TNA as a catalyst in the 7.00 p H value after 60min reactions.（2）The nitrogen-doped TNA（N-TNA）photocatalyst was obtained by TNA precursor（TiO₂ after electroetching treatment,not calcined at high temperature）calcined at 450°C in a nitrogen atmosphere muffle furnace.The morphology and the photocatalytic reaction performance of N-TNA were studied.The results show that the excitation energy of N-TNA photocatalyst decreases to 2.56 e V.Under irradiation of simulated sunlight（200 nm-800 nm）,the 100 m L BPA solution,which the initial concentration was 4 mg/L,was treated with 10cm² N-TNA.Under the condition of 7.00 p H values,the degradation rate of BPA was 82.5%after 60 min reactions.N doping can effectively reduce the excitation energy and improve the BPA degradation efficiency.（3）On the basis of N-TNA study,g-C₃N₄ doped N-TNA（g-C₃N₄@N-TNA）photocatalyst was obtained by impregnation N-TNA with melamine and sealed calcination at550°C in a muffle furnace.The g-C₃N₄@N-TNA characters and photocatalysis property were studied.The results show that g-C₃N₄@N-TNA photocatalyst has absorption in visible light,and the photoexcitation energy decrease to 2.44 e V.Under irradiation of simulated sunlight（200 nm-800 nm）,the 100 m L volume 4 mg/L initial concentration BPA solution was treated with 10 cm² g-C₃N₄@N-TNA.Under the condition of 7.00 p H values,the degradation rate of BPA was 80.4%after 60 min reactions.Doping of g-C₃N₄ effectively reduces the excitation energy of N-TNA,and improves the absorption of visible light.It also improves the transmission efficiency of photo-generated carriers,which have relatively excellent photoelectric efficiency.（4）Based on g-C₃N₄@N-TNA,the Fe₂O₃ co-doped g-C₃N₄@N-TNA（Fe₂O₃/g-C₃N₄@N-TNA）photocatalyst was obtained by impregnation g-C₃N₄@N-TNA with FeSO₄ solution and drying at room temperature.The Fe₂O₃/g-C₃N₄@N-TNA characters and photocatalysis property were studied.The results show that the excitation energy of Fe₂O₃/g-C₃N₄@N-TNA photocatalyst drops to 2.15 e V,which means it has visible light excitation characteristics.Under the irradiation of simulated sunlight（200 nm-800 nm）,the100 m L BPA solution with concentration of 4 mg/L was treated with 10 cm²Fe₂O₃/g-C₃N₄@N-TNA,and the degradation rate of BPA can reach 100.0%after 60 min reactions at 7.00 p H value.The total organic carbon（TOC）removal rate of BPA solution was more than 60%when the light duration increased to 2 h.It is also was found that the hydroxyl radicals（·OH）concentrations are increasing by simulated sunlight illumination time prolong.Intermediates of BPA degradation were tested.The mechanism of Fe₂O₃/g-C₃N₄@N-TNA photocatalytic degradation of BPA is obtained,and the·OH chain reaction can be confirmed as the main reaction during the BPA photodegradation.Furthermore,super oxygen free radicals（O₂^-）which was generated by photo-electron reaction with O₂ also could participate in the reactions,which is the possible cause of good performance of BPA degradation under acid conditions.In this study,the multi-element doped TiO₂ nanotube arrays（Fe₂O₃/g-C₃N₄@N-TNA）photocatalyst was successfully synthesized.The EDCs BPA degradation study under the simulated sunlight（200 nm-800 nm）by the synthesized catalytic was carried out.The possible reaction mechanism of Fe₂O₃/g-C₃N₄@N-TNA photo degradation BPA solution was obtained.It provides a new method on the sunlight photocatalysis degradation EDCs pollutants technology.It also enrichs the photocatalysts research area.