Preparation Of TiO₂ With Ionic Liquid And Photocatalytic Degradation Of Gaseous Toluene

In recent years,with the development of energy,chemistry and other industries,environmental pollution has become a more and more serious problem and volatile organic pollutants have brought serious harm to human health and the environment.At present,photocatalytic oxidation has the advantages of thorough decomposition of pollutants and no secondary pollution for the treatment of volatile organic compounds.In this paper,1-butyl-3-methyl imidazole chloride?[Bmim]Cl?,1-butyl-3-methyl imidazole hexafluorophosphate?[Bmim]PF₆?and phosphonium bromide butylquaternary([P₄₄₄₃]Br)were prepared.A series of TiO₂ was also prepared by sol-gel method assisted by ionic liquid.[Bmim]Cl was selected as the auxiliary agent,and cerium nitrate?Ce?NO₃?₃·6H₂O?and thiourea?CN₂H₄S?were used as the cerium and sulfur sources respectively to prepare the cerium and sulfur doped TiO₂.It was characterized by FTIR,XRD,SEM,BET,XPS and DRS.The factors affecting the dynamic photocatalytic performance of gaseous toluene were studied systematically,such as the type and proportion of ionic liquid,the type and amount of doped elements,initial concentration and flow rate of gas-phase toluene.The dynamic behavior of gas-phase toluene on the modified TiO₂ was also analyzed.The main conclusions are as follows:?1?FTIR analysis showed that [Bmim]Cl,[Bmim]PF₆ and [P₄₄₄₃]Br were synthesized,and the surface hydroxyl content of TiO₂ assisted by ionic liquid is more than that of blank TiO₂.XRD analysis showed that all the samples are single anatase.FE-SEM analysis showed that the prepared samples are spherical nanoparticles with good dispersion.Analysis of pore structure showed that TiO₂ assisted by ionic liquid is mesoporous material,and its specific surface area,pore volume and average pore diameter are all larger than that of blank TiO₂.Among them,TiO₂ assisted by [P₄₄₄₃]Br has a maximum specific surface area of 151.94 m²/g.?2?The photocatalytic degradation performance of gas-phase toluene on TiO₂ prepared with ionic liquids is better than that of blank TiO₂,and its degradation efficiency is significantly affected by the type and amount of ionic liquids.Under the condition of 300 W xenon lamp irradiation for 280 min,the degradation rates of sample prepared with the molar ratio of [Bmim]Cl,[Bmim]PF₆,[P₄₄₄₃]Br and tetra-butyl titanite having 1:5 were 30.29%,26.21% and 27.37%,respectively,while blank TiO₂ was 10.28%.?3?For [Bmim]Cl-assisted TiO₂ samples doped with Ce and S,XRD analysis showed that both samples present obvious anatase crystal type,and the grain size of samples doped with cerium and sulfur decrease.SEM analysis showed that the morphology of each sample is approximately spherical and the dispersion is uniform.Pore structure analysis of samples doped with Ce and S belongs to ? type adsorption isotherm and hysteresis loop is H₂ model.The entrance and the average pore size slightly increase compared with the undoped catalyst.According to XPS analysis,doped Ce ions exist in the form of Ce³⁺ and Ce⁴⁺.For the samples co-doped with Ce and S elements,S element replaced titanium ion to form Ti-O-S bond.DRS analysis showed that the diffuse reflectance spectra of the samples doped with Ce and S elements showed different degrees of redshift,which is significantly lower than the gap width of the blank TiO₂?3.14 eV?,which is beneficial to the absorption of visible light.?4?A series of TiO₂ doped with Ce and S elements and assisted with Bmim]Cl has the better photocatalytic degradation performance of gas-phase toluene than that of undoped TiO₂,and the amount of doping has a significant impact on the degradation rate.Under 500 W xenon lamp illumination for 300 min,the degradation rate of CT-0.5 with 0.5% Ce element content was 45.59% and that of CST-2 with 0.5%Ce content and 2% S content was up to 54.48%.?5?The initial concentration of toluene and gas flow rate also have an effect on the gas-phase toluene photocatalytic degradation on ionic liquid-assisted TiO₂.When the initial concentration of gas-phase toluene increased from 30 ppm to 90 ppm,the degradation rate of CST-2 for gas-phase toluene decreased from 54.48% to 26.81%.When the flow rate of toluene in the gas phase was 300 ml/min,the optimal degradation rate was reached.The langmuir-hinshelwood kinetic model fits well with the experimental data,indicating that this equation is applicable to the photocatalytic degradation of gas-phase toluene by ionic liquid-assisted TiO₂.