Preparation And Photocatalytic Properties Of One Dimension Nano-TiO₂/Muscovite

Nano TiO2, because of its avirulence, harmless, good chemical stability and excellent photocatalytic activity, is in a wide range of applications of wastewater treatment, air purification and the sterilization as a new type of functional nano-material of environmental protection. But nano-TiO2is easily to aggregate and difficult to recycle in the preparation and application, which restrict its actual photocatalytic application seriously. The problem can be effectively solved by finding a right carrier for TiO2-In addition, the low visible-light using efficiency of pure nano-TiO2due to its wide band gap is another reason for limiting the application. The metallic doping, non-metallic doping and codoping to TiO2can effectively reduce the forbidden band width of TiO2so as to show an response to the visible light and improve the using efficiency of sunlight. The formation of one-dimension structures of nano-TiO2can effectively improve the photocatalytic efficiency due to its specific surface area which is larger than that of nano-particles.Using muscovite as the carrier, TiCl4as the source of titanium, urea as the neutralizer, nano-TiO2/muscovite photocatalyst (TiO2/M) was prepared by the method of hydrolysis-precipitation. The influences of the annealing temperature, photocatalyst adding amount, initial concentration of methyl orange and reusing on the degradation of methyl orange were discussed. Using urea as the source of nitrogen, the N-doped nano-TiO2/muscovite composite with visible-light response was then prepared through the calcination. The influences of doping of nitrogen on phase structure, grain size and photocatalytic activity of TiO2and doping mechanism were studied. And then using KOH as the mineralizer, PEG as the mineralizer, nano-TiO2/muscovite with one dimension structure was prepared by hydrothermal synthesis in the autoclave. The influences of KOH concentration and hydrothermal time on the micro-morphology of products were discussed. The samples were characterized by XRD, SEM, EDS, DUV and XPS methods. And the photocatalytic properties of samples were evaluated by the degradation of methyl orange under the irradiation (300W mercury lamp as the source of ultraviolet light,250W halogen lamp as the source of visible light). The results showed that the TiO2coating formed on the muscovite surface densely and uniformly by the method of hydrolysis-precipitation. The TiO2in samples consisted of anatase and rutile. The anatase was transformed to rutile phase as the temperature increased and the grain sizes increased. The photocatalytic activity of the sample after annealing at500℃for2h was the best. The degradation of20mg/L methyl orange under the irradiation of300W mercury lamp for1h with2g/L adding amount of photocatalyst reached97%. After reusing three times under the same condition, the degradation of methyl orange still reached45.3%. The growth of TiO2grain and the transformation from anatase to rutile were restrained by the doping of nitrogen. The nitrogen in TiO2lattice existed mainly in the form of interstitial nitrogen. The absorption edge of the doped sample red-shifted from390nm to430nm due to the formation of Ti-N-0bond so as to reduce the band gap of TiO2, showing an obvious response to visible light. When the quality proportion (powder:urea) was1:3, the degradation rate of methyl orange reached the maximum value of67.15%after the irradiation under250W halogen lamp for1h. After reusing for three times, the degradation rate of methyl orange still reached24.6%. The concentration of mineralization and hydrothermal time had a great influence on the micro-morphology of products during the hydrothermal treatment. The relative best hydrothermal parameter was as follows:the concentration of mineralization KOH was7mol/L, the hydrothermal time was3d and the reaction temperature was150℃. The one-dimension structures of TiO2had formed during the hydrothermal process. The TiO2particles could be dissolved by strong base to be multi-nano-layers and then the nano-layers curled and grew to one-dimension structures under the driving by the alkali stress. The formation of one-dimension structures of nano-TiO2can effectively improve the photocatalytic efficiency due to its specific surface area which is larger than that of nano-particles.