Preparation And Applied Research Of Titanium Dioxide Catalyst Doped With Carbon, Nitrogen And Sulfur

Fomraldehyde is commonly and harmfully detected volatile organic compounds (VOCs) pollutant in the door. The fomraldehyde will result to chronic respiratory disease,cancer, nuclear gene mutation,et al.So,we must pay attention to the pollutant of formaldehyde. Titanium dioxide (TiO₂) photochemical catalysis technology would possess quite development foreground in purifying the indoor air pollution.However, TiO₂ photocatalyst was restricted to purify the indoor air pollution because of itself defect with only absorbing the ultraviolet radiation.The doping modification of TiO₂ is an effective method to improve photocatalytic activity.In allusion to the characteristic of volatile contamination in indoor air,a photocatalyst, TiO₂ doped with C, N and S having visible light excited activity was prepared by the reversed microemulsion.The C,Nand S doping effect and the visible light excited activity were investigated by XRD, XPS and UV- Vis diffuse reflection analysis. And also the photo-catalyzing degrading reactivity of gaseous formaldehyde for the photocatalyst was evaluated.Firstly,TiO₂ particles have been prepared by chemical reactions between TiCl₄ solution and ammonia in water/(TX-100 +n-pentanol)/cycloheptane reversed microemulsion systems. The influences of [water]/[TX-100] mole ratios (ω), the concentrations of TiCl₄ ,pH and sintering temperature on the composition, structure and UV-Vis light absorbency of the TiO₂ were explored.The results showed that the particles have hollow structures and the shell thickness of TiO₂ hollow spheres is affected by the concentrations of TiCl₄. The anatase titania was only confirmed by XRD analysis when calcined at 600°C ,and with an increase of temperature ,the crystallite sizes of TiO₂ increased from 8.14 to 15.4nm. The diffuse reflectance spectra showed theUV-Vis absorption intensity of self made TiO₂ is superior to the standard photocatalyst P25.Based on the obtained results,using the ABS, TiCl₄ and ammonia as the raw materials, the in situ compound of SPAN/ TiO₂ were prepared in reversed microemulsion systems. The effects of dosage of the dopant, sintering temperature and sintering time on the composition, structure and UV-Vis light absorbency of the C, N and S doped TiO₂ were studied. The results showed that One part of C,N element in the SPAN incorporated into TiO₂ crystal lattice in the form of interstitial carbon and nitrogen,while the another part of C,N element in the SPAN incorporated into TiO₂ crystal lattice in the form of replacing-carbon and nitrogen via the process of replacement of O 2- of TiO₂.In addition,the S element in the SPAN replaced Ti4+ with S4+ of TiO₂ crystal lattice;C, N and S doped TiO₂ can be achieved using the above compounds,and UV-Vis absorption spectrum revealed that the prepared catalyst presented intensive absorption both in ultraviolet and visible light region; meanwhile, the ultraviolet absorption peak created red shift;The doping catalyst of TiO₂-500-3-0.05 has the good impact of visible light excited activity.The photocatalysis action device was designed independently and used to imitate the indoor pollution of formaldehyde. The roles of reaction conditions such as the initial concentration of formaldehyde,the calcined temperature,time,doping content and the light intensity were studied using the photocatalyst of TiO₂-500-3-0.05 by contrast.The results showed that with the increase of calcined temperature,the degradation ration of gaseous formaldehyde decreased; The degradation ration of gaseous formaldehyde inceased with the increase light intensity; The degradation ration of gaseous formaldehyde after the photocatalyst calcined for 3h is better than others;So,the degradation ration of gaseous formaldehyde is better than others when we choice the photocatalyst of TiO₂-500-3-0.05; The initial concentration of formaldehyde is lower,the degradation ration is higher when the concentration of formaldehyde is 0.71-14.2mg/m3; The degradation ration of gaseous formaldehyde yielded threshold maximum 66% while the initial concentration of formaldehyde is 14.2 mg/m3; Gas-phase photo catalytic degrading reaction of formaldehyde conformed L-H dynamics model ,and the degrading reaction conformed to first order reaction.