Preparation Of Flexible TiO₂-based Composite Fiber Membrane By Electrospinning And Study Of Its Pollutant Degradation Performanc

At present,with the rapid development of human industry and agriculture,the problem of environmental pollution is more and more serious.Water is an important resource that people depend on for survival.A large number of organic pollutants in water will seriously affect the ecosystem and cause unpredictable consequences.As an efficient,controllable and less polluting technology,photocatalysis has attracted much attention.Titanium dioxide（TiO₂）plays an important role in various fields due to its strong oxidation,non-toxicity and superior chemical stability.However,TiO₂ also has shortcomings that cannot be ignored:low utilization rate of visible light,easy recombination of photogenerated electron-hole,easy agglomeration and secondary pollution.Aiming at the above problems,TiO₂ was modified in this paper.The catalyst with fiber membrane structure was prepared by electrospinning technology,which solved the problem of secondary pollution,expanded the range of photoresponse of TiO₂,and improved the utilization rate of visible light.The visible light degradation performance of composite fiber film catalyst was investigated.The prepared catalyst has the characteristics of convenient recovery and high recombination rate.The main work is as follows:（1）Polythiophene/graphene quantum dots/TiO₂（PTh/GT）,polypyrrole/graphene quantum dots/TiO₂（PPy/GT）and polyaniline/graphene quantum dots/TiO₂（PAn/GT）ternary composite fiber film catalysts were prepared by electrospinning,hydrothermal method and in-situ polymerization technology.Through the characterization of morphology and structure,the successful recombination of ternary catalyst was proved.Visible light catalytic experiments showed that the composite membrane catalysts had excellent degradation performance.The photodegradation rate constants of PTh/GT for methylene blue(MB 10 mg L^-1)and tetracycline hydrochloride were as high as 1.1×10^-2min^-1 and8.7×10^-3 min^-1,respectively.It is more than 4 times and 11 times of pure TiO₂ composite membrane catalyst,and the regeneration efficiency can be maintained above 90%.It is worth noting that various experimental results show that the introduction of graphene quantum dots（GQDs）regulates the band gap of TiO₂,resulting in the formation of an internal electric field between GQDs/TiO₂ and PTh,which promotes the outflow of electrons at the TiO₂ conduction band and combines with the photogenerated holes at the highest occupied orbital of PTh.Therefore,the interfacial charge transfer mechanism between GQDs/TiO₂ and PTh follows the Z-type heterojunction,which maximizes the REDOX capacity of the system.（2）A flexible 1T-WS₂/TiO₂ composite fiber membrane catalyst was prepared by electrospinning and hydrothermal method.The composite membrane catalyst had good conductivity and abundant active sites.The load of 1T-WS₂ can be accurately controlled by adjusting the molar ratio of W and Ti.The photocatalytic activity of different proportions of 1T-WS₂/TiO₂ at visible light degradation of 20 mg L^-1 MB was studied.Degradation rate constant of 1T-WS₂/TiO₂ under visible light is 1.032×10^-2 min^-1,which is 30 times that of pure TiO₂ fiber film.The full spectrum absorption characteristics of 1T-WS₂ broadened the visible light absorption range of TiO₂ fiber film and increased the utilization rate of visible light.In addition,1T-WS₂ can capture photogenerated electrons and has strong electron transfer characteristics,which promotes the effective separation and transfer of photogenerated carriers.Therefore,1T-WS₂/TiO₂has better photocatalytic performance in photocatalytic degradation of MB.This study not only proves that TiO₂-based flexible fiber film can be used as a kind of environmentally friendly catalyst,but also provides a reference for future researchers to develop green photocatalytic technology.