Research On Photocatalytic Degradation Of Gaseous Toluene By Ag/AgCl@TiO₂-LDHs Composite

For the past few years,volatile organic pollutants(VOCs)released by human factors have threatened the ecological environment and human health seriously,so how to control the VOCs pollution has become a hot topic in the field of environmental research.Photocatalytic technology has attracted much attention by scholars all over the word owing to its great advantages such as mild reaction conditions and simple process.TiO2 is the most widely used photocatalyst because of good chemical stability,low cost and non-toxic.It can effectively degrades organic pollutants to CO2,H2O and inorganic ions under ultraviolet or sunlight irradiation.However,the high recombination rate of electron-hole pairs limits the quantum yield of TiO2,and the low utilization rate of visible light is also an important factor limiting its photocatalytic efficiency.Therefore,the modification of TiO2 was studied in this paper,aiming at improving the photocatalytic performance by preparing composite catalyst.Gaseous toluene was selected as model compound for evaluation of the photocatalytic performance of the catalyst under simulated sunlight using pseudo in situ measurement.The main research contents are as follows:(1)The composite catalyst Ag/AgCl@TiO2-LDHs was successfully prepared by selecting MgAl-LDHs as the substrate,hydrolyzing butyl titanate to produce TiO2 nanoparticles supported on the surface of LDHs sheet,and then doping Ag/AgCl with photoreduction method.The catalyst was systematically characterized by means of XRD?SEM-EDS?TEM?HRTEM?XPS?FT-IR?TGA?UV-vis and BET analysis.Results showed that the composite catalyst Ag/AgCl@TiO2-LDHs has high crystallinity and enhanced absorption of visible light.Besides,obvious lamellar structure of MgAl-LDHs provides large specific surface area for the adhesion of TiO2 and Ag/AgCl particles.(2)Pseudo in situ measurement was chose to measure the concentration of gaseous toluene,and the feasibility of this method was analyzed by precision and stability experiments.The experimental results of photocatalytic degradation of gaseous toluene showed that the composite catalyst Ag/AgCl@TiO2-LDHs exhibited excellent photocatalytic activity.The degradation rate was up to 92%under simulated sunlight and it could still reach 87%after five cycles,and also showed excellent photocatalytic activity to RhB solution.(3)In order to further study the catalytic properties of Ag/AgCI@TiO2-LDHs,the initial concentration of pollutants and the addition amount of catalyst were changed.It was observed that the higher the concentration of pollutants is,the lower the photocatalytic degradation rate of the catalyst is.The more the amount of catalyst added,the higher the photocatalytic degradation rate of pollutants is,but the photocatalytic activity gradually decreased when the amount of catalyst was added exceed the optimal amount.Dynamics research was carried on,and the photocatalytic degradation process was consistent with the pseudo first-order kinetic model.(4)Based on the characterization results and degradation results of gaseous toluene and liquid RhB,the possible degradation mechanism of pollutants were also proposed in this paper.In addition to the effect of electron trapping trap and surface plasmon resonance of Ag nanoparticles,there are many hydroxide ions and interlayer water molecules in LDHs hydroxide laminates.All of them play important roles in the degradation of pollutants.