Study On The Degradation Of Environmental Pollutants Using F-doped TiO₂ Supported By Exfoliated Bentonite

With the increasing development and advancement of social economy,people are also facing a series of environmental pollution problems while enjoying high technology and convenient life.Air pollution is one of the most important issues.Indoor air pollutants are mainly volatile organic compounds(VOCs),such as formaldehyde and toluene.VOCs are not only harmful to human health,but also a major culprit of air pollution.VOCs are an important precursor of PM2.5 and photochemical smog,so how to efficiently treat and purify such indoor air pollutants becomes a significant problem.People are paying close attention to many technologies that have been applied to the purification treatment of indoor polluted air in the country.Among lots of treatment and purification methods,photocatalysis technology has become one of the most promising technologies due to its simple process and mild reaction conditions.Advanced oxidation materials represented by titanium dioxide are one of the earliest photocatalytic materials to be studied.However,there are still many problems in the application of titanium dioxide materials.For example,titanium dioxide has the disadvantages of wide band gap,easy agglomeration,and difficulty in recycling.In order to solve the agglomeration problem of titanium dioxide nanomaterials and improve the photocatalytic efficiency,this work prepared a fluorine-doped titanium dioxide photocatalytic material supported by exfoliated bentonite.Using tetrabutyl titanate as the titanium source,the typical sol-gel method is used to prepare the titanium dioxide material.The fluorine ions are doped into the titanium dioxide by the chemical stirring and dissolution method,and then the fluorine-doped titanium dioxide nanomaterial is loaded on the surface of the exfoliated bentonite.A series of F-TiO2 and F-TiO2 nanomaterials with excellent photo catalytic performance were prepared.The very popular indoor air pollutants toluene and formaldehyde were used in experiments and the photocatalytic activity was performed by removal of toluene and formaldehyde.The structure and optical for photocatalytic degradation were analyzed by using XRD,SEM,XPS,BET,EPR and other characterization techniques of prepared materials.The main research contents and conclusions are as follows:(1)Titanium dioxide nanomaterials were successfully prepared using the traditional sol-gel method,using ammonium fluoride as the modifier and doping fluorine ions into the titanium dioxide through a chemical dissolution method.A series of different fluorine ratio doped materials were prepared by effective high-temperature calcination.Mixed titanium dioxide nanomaterials,analyzed and characterized by XRD,SEM,XPS,etc.(2)Use liquid phase intercalation dispersion method to exfoliate bentonite.The XRD and SEM characterization results show that the 2:1 natural layered bentonite was successfully exfoliated into thin slice bentonite,and the clear slice bentonite structural unit can be seen from the SEM image.(3)Using the exfoliated bentonite as a support framework,fluorine-doped titanium dioxide nanomaterials were loaded on the exfoliated bentonite.XRD and SEM as well as TEM analysis results showed that the fluorine-doped titanium dioxide nanoparticles were evenly distributed on the exfoliated bentonite.(4)By degrading the prepared pollutants toluene and formaldehyde,the photocatalytic performance of the sample was tested.The calcination temperature of the sample,the amount of fluoride ion doping and the support of the exfoliated bentonite have a great influence on the photocatalytic performance.The degradation experiment results show that the fluoride ion doping content of the exfoliated bentonite calcined at a high temperature of 400℃ is 5%of the titanium dioxide sample,and the degradation and removal rate of toluene and formaldehyde can reach 86%and 81%.After XPS,EPR and FTIR analysis and characterization,shows that part of the fluoride ions will remain on the surface of titanium dioxide,and part of the fluoride ions will enter the titanium dioxide lattice to produce oxygen vacancies and Ti3+defects.The generation of oxygen vacancies and Ti3+is beneficial to photocatalytic degradation of pollutants and improves the photocatalytic performance of the sample.