Doping / Load Of Tio <sub> 2 </ Sub> Preparation, Characterization And Processing Applications Of Formaldehyde

The photocatalysis of nanometer titanium dioxide(TiO₂) has been considered as the most promising technique for treating contaminated environment and exploiting energy sources because of its strong oxidizing power, complete mineralization of pollutants, without secondary pollution and excellent photocatalytic degradation of various refractory compounds on normal temperature with the use of ultraviolet(UV) light as the energy source. However, anatase TiO₂ can only be induced by UV light. Furthermore, TiO₂ nanoparticles have a tendency to flow away in treating contamination and are recycled difficultly. So it is an effective method for solving these problems through doping modification and immobilizing of TiO₂. In this paper, doping and immobilizing TiO₂ were investigated by treating formaldehyde for seeking after its application.An effective approach to shifting the optical response of TiO₂ from the UV to the visible spectral range is the doping of TiO₂ with nonmetal nitrogen. In this paper, TiO₂-xNx photocatalysts, which can respond to visible light, were prepared by a Sol–gel method using urea as nitrogen source. The effects on photocatalytic activity of calcination temperature, calcination duration, materiel ratios and pH value of hydrolyzing solution were investigated through degrading formaldehyde and kinetics was researched about photocatalytic degradation of formaldehyde with TiO₂-xNx. The experimental results showed: Under these conditions that hydrolyzing temperature was 30℃, Ti(OBu)4:C2H5OH:NH(C2H4OH)2:H2O:CH4N2O=1:23.32:1:4:0.06, pH value of hydrolyzing solution was about 5, calcination duration was 3 hours under 500℃, TiO₂-xNx was of high photocatalytic activity and the degradation rate of formaldehyde was 70.18%. And the reactions of degrading formaldehyde with TiO₂-xNx prepared with different factors and levels under visible light followed first order kinetic disciplinarian.The structural and photoelectric properties of such photocatalysts were characterized by XRD,DSC,TEM and XPS. The XRD results showed: Calcining temperature had important effect on the crystal phase and particle size of TiO₂-xNx, the doped entire samples exhibited anatase structure at 400℃, and their particle size was 13.9nm, when temperature rised sequentially, the crystal sizes of the samples increased, and rutile phase started to appear and its relative abundance increased. The doped entire samples exhibited rutile structure at 700℃, and their particle size was 51.2nm. The doping of N can enhanced the photocatalytic activity under visible light of TiO₂ obviously, but it had little effect on the crystal phase and particle size. N1s XPS spectra of TiO₂-xNx exhibited a absorption peak at 399.6eV which belonged to Ti-N bond and was introduced through N instead of O which responded to visible light.AC/TiO₂ photocatalyst was prepared by the Sol-gel method and characterized by SEM and BET. And it was applied to treating formaldehyde simulate wastewater and formaldehyde simulate gas. The results of treating formaldehyde wastewater showed: Under the conditions, formaldehyde wastewater's initial concentration 30mg/L, pH value 13, the dosage of AC/TiO₂ photocatalyst 4g/L, the illumination time 3h under the irradiation of 40W UV-light, the degradation rate of formaldehyde wastewater was 96.6%.The results of orthogonal experiment showed that the effect order of primary factors was pH value﹥illumination time﹥dosage of photocatalyst, and the affections of pH valve of formaldehyde wastewater and the illumination time were very remarkable to the experimental result at the level ofα=0.05. After the AC/TiO₂ photocatalyst was used repeatedly at the sixth time, the degradation rate of formaldehyde wastewater was over 92% and it had an promising foreground. The results of treating formaldehyde gas showed: Under the conditions, formaldehyde gas's initial concentration 8.39mg/m3, the dosage of AC/TiO₂ photocatalyst 5g, the illumination time 15 min under the irradiation of 400W UV-light, the degradation rate of formaldehyde gas was 99.4%. TiO₂ were dispersed on the AC or in the bore and were of big BET as the AC. AC/TiO₂ bringed cooperation into play, that is, the absorption of AC can provide big contaminated concentration for TiO₂ and the photocatalysis of TiO₂ can realize regeneration of AC.