Preparation,Modification And Photocatalytic Activity Of Water-dispersed Nano-TiO₂

Titanium dioxide(TiO2)has the advantages of environmental protection,high catalytic efficiency,biocompatibility,high stability and low cost,and is widely used in environmental protection and energy.This paper mainly introduces the photocatalysis principle,common preparation methods and modification methods of nano-TiO2.Ti02 has a large band gap(3.2 eV),which is only responsive to ultraviolet light in solar radiation,and its visible light catalytic activity is very low.Many applications of TiO2 are mainly implemented in the form of dispersions,including photocatalyst products for decoration,self-cleaning glass and coatings.Therefore,the preparation of nano-TiO2 with good water dispersibility and visible light activity has wide application significance.In this paper,nano-TiO2 with visible light photocatalytic and dispersion stability was prepared by non-hydrolyzed sol-gel method.The main research contents and conclusions are summarized as follows:1.Using titanium tetrachloride as titanium source,ethanol as solvent and oxygen donor,nano-TiO2 was prepared by non-hydrolysis-sol gel method.The visible light activity of TiO2 was evaluated by photocatalytic degradation of methyl orange(MO)by visible light.The effects of ethanol dosage,heat treatment temperature and heat treatment time on the visible light photocatalytic performance of nano-TiO2 were investigated.The anatase phase TiO2 was synthesized at a volume ratio of titanium tetrachloride to ethanol of 4:5,heat treatment time of 8 h and heat treatment temperature of 150 ?.The microstructure of the anatase phase was mainly in the form of a fusiform sheet with a size of 10-20 nm.The UV-Vis absorption spectrum showed that Ti02 had light absorption in the visible region.FI-IR analysis indicated that TiO2 had surface hydroxyl groups,and surface hydroxyl groups could react with photogenerated holes to form-OH to promote redox reaction and could become an active adsorption center.The TiO2 powder was formulated into a dispersion with a mass fraction of 1%.After standing for 60 days,the mass fraction of the supernatant was 0.84%,indicating that Ti02 had good dispersibility in water.The electric double layer,hydroxyl group and small particle size on the surface of the TiO2 particles are favorable for their stable dispersion in water.Degradation MO experiment under visible light,the degradation rate of self-made TiO2 was 35.59%,which was greater than 28.88%of domestic Ti02.The degradation rate of imported TiO2 was 35.68%,and the visible light catalytic performance of self-made TiO2 was similar to that of imported TiO2.2.Using titanium tetrachloride as titanium source,anhydrous ethanol as solvent and oxygen donor,Ce(NO3)3,Pr(NO3)3,La(NO3)3 as dopant,prepared the rare earth modified nano TiO2.The effects of different elements and different doping ratios on the visible light catalysis of TiO2 were investigated.XRD characterization showed that TiO2 was still anatase after doping;In the EDS spectrum of doped Ti02,characteristic peaks of Ce,Pr and La were observed respectively,indicating that Ce,Pr and La were doped in TiO2;The UV-Vis absorption spectrum showed that the absorbance of doped TiO2 in the visible range of 400-800 nm was significantly higher than that of pure TiO2;Under TEM,the microstructure of TiO2 was mainly in the shape of irregular sheets,and the size was about 10-20 nm.The results of photocatalysis experiments showed that the visible light photocatalytic activity of Ce-TiO2,Pr-Ti02 and La-TiO2 increased with the increase of doping ratio,but decreased when the optimal doping amount was reached.This was mainly due to the fact that the photogenerated electron-hole pair recombination could not be effectively suppressed when the doping ratio was low;When the doping ratio was too high,a recombination center of electron holes was formed among them.The optimum doping ratios of Ce-Ti02,Pr-TiO2 and La-Ti02 were 4%,3.5%and 3%,respectively.The degradation rates of MO were 86.51%,76.14%and 57.70%,respectively;The undoped TiO2 was only 35.59%.The degree of enhancement of visible light catalytic activity of TiO2 by Ce,Pr and La doping was Ce>Pr>La.