Degradation Of Gas Phase Benzene Using Metal-nonmetal Doped TiO₂ Under Visible Light

VOCs are harmful compounds,which can produce secondary pollutants?including organic compounds and organic aerosols?by combining with other substances in the atmosphere.Also,they are precursors of ozone,so they have attracted widespread attention.Photocatalytic is considered as one of the most promising purification methods to degrade VOCs due to its better environmental friendly features.For many photocatalysts,TiO₂ has been a research hotspot due to its advantages such as low production cost,simple preparation,strong thermo-chemical stability,and thorough degradation of pollutants.However,the following defects still exist in the photocatalytic degradation of VOCs by TiO₂:?1?the large band gap limits its use of visible light;?2?the probability of photo-generated carrier recombination is large,which limits its efficiency of photocatalytic degradation.In order to solve above problems and draw on many literature research experiences,this experiment used the sol-gel method based on the previous research of this research group.Using I as a non-metal source?the previous research results of this research group?,M?Co,Mn,Cr?as the metal source,the M-TiO₂ and M-I-TiO₂ were prepared.Then using benzene as the target,the photocatalytic performance of the prepared catalyst were investigated under visible light.The main research results are as follows:?1?M-TiO₂ was prepared by sol-gel method.The effects of the doping amount of M and calcination temperature on the degradation of benzene under visible light were investigated.The results showed that the photoresponse range of TiO₂ can be extended to the visible light region by the doping of trace M elements;the photoactivity of each catalyst can be ordered as follows:?Cr/Ti?_0.02-450>?Mn/Ti?_0.04-300>?Co/Ti?_0.01-400,the treatment capacity of benzene was 552.65?gC₆H₆/?g·h??515.96?gC₆H₆/?g·h?and 404.33?gC₆H₆/?g·h?;XRD characterization showed that the main crystal forms of M-TiO₂ was an anatase phase,the particle size was significantly reduced,and lattice defects were increased to a certain extent compared to homemade TiO₂;XPS characterization showed that the proportion of hydroxyl groups or adsorbed oxygen on the surface of TiO₂ in Cr-TiO₂ is much higher than that of Co-TiO₂ and Mn-TiO₂.?2?A response surface experiment was designed using the rotating combination method to determine the optimal M-doped amount,I-doped amount,and calcination temperature of M-I-TiO_2.Then XRD,BET,Raman,XPS,and UV-vis characterization analysis were performed on the selected optimal M-I-TiO₂.The results showed that the photoactivity of each catalyst can be sorted as:?Cr/I/Ti?_0.02/0.1/1-400>?Co/I/Ti?_0.01/0.1/1-350>?Mn/I/Ti?_0.02/0.15/1-400,and the treatment capacity of benzene was 678.82?gC₆H₆/?g·h??441.46?gC₆H₆/?g·h?and 389.54?gC₆H₆/?g·h?;The primary crystal form in M-I-TiO₂ was an anatase phase,the particle size was significantly reduced,and the specific surface area was significantly larger than that of I-TiO₂;Raman results showed that the characteristic peaks of M-I-TiO₂ under vibration state of 147cm^-1 had different extent blue-shifted than I-TiO₂;The ratio of hydroxyl or adsorbed oxygen on the surface of TiO₂ in Cr-I-TiO₂ was much higher than Co-I-TiO₂ and Mn-I-TiO₂;?Co/I/Ti?_0.01/0.1/1-350??Mn/I/Ti?_0.02/0.15/1-400 and?Cr/I/Ti?_0.02/0.1/1-400 forbidden band widths were:3.05 eV?403nm?,3.01 eV?412nm?,and 2.85 eV?435nm?.?3?Using three optimal co-doped catalysts?Co/I/Ti?_0.01/0.1/1-350??Mn/I/Ti?_0.02/0.15/1-400 and?Cr/I/Ti?_0.02/0.1/1-400,the experiments were carried out to study the effects of residence time,catalyst dosage and initial benzene mass concentration on the photocatalytic performance of the catalyst.The results were as follows:For?Co/I/Ti?_0.01/0.1/1-350,when the residence time was 80s,the amount of catalyst used was 8g,and the initial mass concentration of benzene was 200±20mg/m³,the catalyst treatment capacity reached the highest?491.99?gC₆H₆/?g·h??;For?Mn/I/Ti?_0.02/0.15/1-400 and?Cr/I/Ti?_0.02/0.1/1-400,when the residence time was 80s,the amount of catalyst used was 8g,and the initial mass concentration of benzene was 100±20mg/m³,the two catalysts'processing capabilities reached the highest?454.91?gC₆H₆/?g·h?and 750.49?gC₆H₆/?g·h??.