Preparation Of TiO₂ Photocatalytic Coatings And Research On Degradation Rate To Formaldehyde Of The Coatings

Formaldehyde is one of the main indoor contaminations. Coatings which as the most common indoor building materials have became the most important source of the formaldehyde pollution. Formaldehyde does harm to people, anyone who absorb too much will be likely to be death, so people are increasingly pay more attention to the purification capacity of coatings. Because of the rapid react speed,the short react time,non-selective,low react temperature(room temperature is ok),non-toxic catalyzer,simple equipment and low cost, Photocatalytic technology of semiconductor is be regarded as the most promising technology in the indoor air pollution-purification, it is also be regarded as the most ideal technology, TiO₂ of course became the most ideal photocatalyst because of its efficient and environmentally features.In this paper, experiments were developed based on this social background. The main work is on the preparation of TiO₂ photocatalytic coatings,on the Characterization of coatings' regular capability and on the influence factors to photocatalytic capacity, at the same time, on the durability of the coatings. The details are as follows:1. Selected dispersant throughout the intuitive method: rheological and sedimentation. It was found from Rheological method that as the mass rat of dispersant and TiO₂ powder vary from 0.04 to 0.12, both the five dispersant Lopon®890,Orotan,Cognis875,Cognis3204,FX-106 appeared fluid phenomenon at the rat of 0.08 , they also had good rheology; It was found from sedimentation that the deposition layer was the thinnest with adding of Lopon®890, it could be demonstrate from TEM that the dispersant had good effect on scattering TiO₂.2. Selected TiO₂ photocatalytic material from purification experiment. The experiment result indicated that the effect of TiO₂ powder is better than that of liquid, the effect of TiO₂ powder which with Cu metal-doped is better than SiO₂-doped and pure, the TiO₂ powder with Cu impure realized the TiO₂ 's respond in the range of visible light.3. The regular capability of the coatings which modified by Photocatalytic materials are up to the mustard. The degradation to formaldehyde reached 75% in 24 hours. Many factors influenced the degradation to formaldehyde of the coatings. The experiment result indicated: the degradation to formaldehyde of the coatings rised when the temperature vary from 18℃to 28℃; the degradation rised at first and dropped down in the end as the humidity vary from 30% to 80%,the trend is not always the same; the degradation dropped down as the amount of formaldehyde solution vary from 5μL to 20μL; the degradation under the daylight lamp is higher than that with the UV condition; the thickness of the coatings had little effect on the degradation; definite wind speed was good for Photocatalytic reaction, but this didn't work when the wind is too strong.4. The degradation to formaldehyde of the coatings reached 75%, and the degradation still reached 65% after 4 days' saturation experiment.