| With the high-speed development of social economy in China,the issue of the deterioration of natural environment is more and more sever.Therein the most obvious problem is the haze which is in the north of China in winter.The photocatalysis technology has capacities in degradating pollutants and eliminating harmful gas.Therefore we can take advantage of nature sunlight,use the abundant outer walls as the supporter and add photocatalysts into ordinary coating to eliminate SO2,NOx and its like.Titanium dioxide is a white pigment and mainly contains anatase and rutile types,among these rutitle is extensively used in paints because of its high whiteness and low photocatalytic activity.Anatase could be added as an additive to the paints to remove harmful gases due to its high photocatalytic activity.However,anatase’s high photocatalytic activity leads to yellowness of the base material and pulverization if it is directly used as an additive in paints.Therefore,the photocatalytic activity of anatase should be control.In addition,it is a problem that TiO2 nanoparticles tend to aggregate because of its small diameter and strong polarity.The features limit its dispersion in the paints.In this paper,the following three parts have been done to solve the above two problems.The silica shell structure deposited on the surface of titanium dioxide by chemical deposition method can form a barrier between contaminants and titanium dioxide to control the photocatalytic activity of anatase titanium dioxide.And then take advantage of organic matters,such as OTMS and KH-550 to enhance the dispersibility in dispersed phases.The last,the products are used in eliminating SO2.The sections in this work can be concluded as followed:(1)The SiO2 inert shell was coated on the surface of anatase by chemical deposition method,in which low-cost sodium silicate and Billions BLA-200 titanium dioxide were used as raw materials.The relationship between the reaction pH,the reaction temperature,the concentration of sodium silicate,the Si/Ti and the photocatalytic activity was studied.It was found that the acidic,neutral and strong alkaline conditions were not favorable for the formation of the silica shell on the surface of titanium dioxide and the optimal pH range was 9～11.When the temperature was between 30～90℃,the photocatalytic activity increased with the rise of temperature,and the optimal reaction temperature range was 70～90℃.When the concentration of sodium silicate was in the range of 0.1～0.8 mol/L,the photocatalytic activity increased with the increase of the concentration,and 0.1～0.3 mol/L was the optimum concentration range.Under optimal conditions,when Si/Ti was in rage of 1/30～1/7.5,the photocatalytic activity was reduced with the increase of Si/Ti.Simultneously,the regulation of the titanium dioxide shell thickness and photocatalytic activity was achieved.The results show that the thicknesses of the shell are 0 nm,3.5 nm,5.8 nm,7.4 nm,8.1 nm,12.3 nm,and 15.4 nm,and the corresponding photocatalytic activities are 91.8%,83.1%,74.3%,60.2%,31.6%,28.4%and 10.7%,respectively.The A02 anatase sample was used as comparative tests and verified the universality of the silica shell structure by liquid deposition.(2)TiO2@SiO2 was re-dispersed by using distilled water,ammonia,maleic anhydride octadecene copolymer,silane coupling agent OTMS and KH-550.TiO2@SiO2 co-modified by OTMS and maleic anhydride octadecene copolymer can stably disperse in ethanol for 24 h and more.However,the photocatalytic activity of titanium dioxide was sheltered strongly.The sample TiO2@SiO2 modified by KH-550 cannot be stable in ethanol solution,but it can be stable in the water for 12 h and the photocatalytic activity of titanium dioxide was shielded weakly.So KH-550 is more suitable as a modifier for the TiO2@SiO2-K sample,which is suitable for water-based coating.(3)The property of photocatalytic elimination of SO2 in TiO2@SiO2-K samples was investigated by the addition of the fractional aniline to formaldehyde solution with the determination of spectrophotometer.TiO2@SiO2-K samples can eliminate SO2 gas under light and the photocatalytic activity is consistent with the regulation in(1)and the photocatalytic stability is good.The initial goal that the regulation of photocatalytic activity,good dispersion in the water phase and photocatalytic elimination of SO2 is achieved.In this paper,the anatase TiO2 was inorganic-organic treated combining the advantages of both inorganic-coating treatment to control the photocatalytic activity of titanium dioxide and organic treatment to improve the dispersibility of titanium dioxide.Sodium silicate and silane coupling agent are inexpensive and the experimental methods are simple. |
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