Hot Water Solution Preparation Of Nano Tio <sub> 2 </ Sub> And Its Films

Nanometer TiO₂ exhibits some unique dielectric and chemical properties that can be utilized in many fields such as photocatalysis, ceramic membranes, gas sensors, environmental protection and so on. The key question of preparing nanometer TiO₂ is the low-cost process. In this paper, the hydrous TiO₂ has been prepared by thermohydrolysis method with industrial titanic solution.Firstly, in the thermohydrolysis system, the effects of the technical parameters of hydrolysis on the particle size and yield of TiO₂ have been studied. The results show that the particle size and the yield of the TiO₂ are influenced by the process parameters including acidity, TiOSO₄ concentration , temperature and time of hydrolysis. The optimal technologic parameters for the hydrolysis are: the titanic solution concentration 28g · L^-1, H⁺ concentration is 2.8 mol · L^-1, hydrolysis temperature 125℃ and hydrolysis time 60min. Based on above condition, the recovery of titanium over 96% and the particle size of TiO₂ is about 120nm.The effects of species and contents of the surfactants on the dispersion of TiO₂ have been studied. The results indicate that adding surfactants is propitious to reduce the particle size of TiO₂ and aggregation. The compound surfactants including 1.0wt%DBS and 0.5wt% PEG6000 is found to be the most effective influence on the hydrolysis and the size achieved particle TiO₂ ranges between 40 and 55nm; the effect of anionic with 1.5wt% DBS surfactants is inferior to the former and the obtained TiO₂ is about 75nm; the non-ionic such as PEG6000 with 2wt% content can also alleviate the aggregation of powders and the particle size of TiO₂ is in the range of 90-100nm; the cationicsurfactants have the minimum effect on the reducing aggregation of TiO₂ powders, when the content of TEA is up to 1.0wt%, the aggregation is little improved and the particle size of TiO₂ is in the range of 100-120nm.The film of TiO₂ has been prepared by using the dip-coating method with the waste solution of hydrolysis. The results show that the film ofnano-TiO₂ is kept anatase structure treated below 750℃; SEM analysis indicates the film is combined tightly with glass and it has the photo-hydrophilic properties, heat-hydrophilic properties, permeability and photo-catalytic activity. The film of TiO₂ has been prepared by using the dip-coating method with the waste solution after hydrolysis. The film after dipping five times is treated at 500℃ for 1 hour and the transmittance is above 90% with wavelength range of 600-800nm, the rate of degradation of methyl orange on the film with five-layer films, after treating by ultraviolet radiation for 3.5 hours, is up to 95%.