Application Of Nano-TiO₂ In The Environment Protection And Sanitation Field

Titanium dioxide might be the most potential photochemical catalyst due to its cheapness, innocuity, and stability. Currently, nano-TiO₂ has been widely applied in the environmental health field for it excellent photochemical property, including effluent treatment, air purification and disinfection and so on. However, many technical matters in the application of nano-TiO₂ should have to be settled as soon as possible, such as the dispersion of the catalyst, the photo catalysis activity and the immobilization methods. So the dispersivity, photocatalysis activity, and immobilization methods would be the chief research topics.In this paper, many attentions were mostly focused on the problems mentioned above. At first, the nano-TiO₂ and nano-ZnO were prepared with the direct precipitation method. The effect of ultrasonic and pH value on the dispersion and stabilization of the suspension system were discussed. The results showed that lasting ultrasonic vibration was the decisive factor to the dispersion of system, and the pH value would greatly influence the stability of the suspension system. It was found that the degradation ratio of HCHO could be upward of 97% in the dispersed liquid at pH=9.5 under 48 hrs ultrasonic vibration, and the relatively steady degradation effects could be getten after reused for several times.Secondly, the nano-TiO₂ composited dispersion was applied in the degradation of residual formaldehyde in the fabric which has been soaked in formaldehyde solution to simulate the degradation of the residual formaldehyde in practical fibric. The results revealed the great influence of technique conditions on the degradation of formaldehyde. The increase of catalyst could shorten the degradation time, and itmade a high formaldehyde-degraded ratio within the optimal reaction time 5-6hrs. After photo-catalytic degradation, the remnant concentration of formaldehyde could be lower to the control regulated by the national standard; furthermore, the relative short degradation time could not lead the aging of fabric by irradiation. Under alkalescence, the degradation of formaldehyde in fabric was faster than others relatively, because the reaction of formaldehyde-degraded might be accelerated by the formation of -OH. The degradation efficiency of catalyst was higher by spraying than by dipping, and UV made a higher degradation of formaldehyde than Short-UV, because the UV could be easily absorbed by Nano-TiO2. With the increase of light intensity, photocatalysis rate increased, however, a light intensity over given range could lead fabric to be aged. Then, the nano-TiC>2 composited dispersion was applied in the degradation of the residual formaldehyde in the easy-care finishing solution and easy-care finishing fibric. The results confirmed that the residual formaldehyde in the easy-care finishing fibric could not be played down by this photocatalytic oxidation technique although the degradation was still carried on, because the instable resin would be continuous continuously decomposed with the degradation. This result would offer some valuable experiences for the following researchers.At last, Silica-sol was used as adhesive and PVA as aid- adhesive to immobilize photo-catalyst as the coating film. Synthetically considering the porperities of the films, the contents of catalyst, silica-sol and PVA should be respectively 50-70g/L, 15g/L and 2g/L in the dispension. The macro-capability and micro-capability performance of the film have been investigated. The result showed that this fim could meet the need of application due to its excellent performances such as photo-activity, heat-resistibility, water-resistibility, corrosion protection, adhesion, and aging-resistibility. This method immobilized catalyst under room temperature would play an important role in the application of the photocatalysis technique.