The Experimental Research On The Degradation Of Indoor Formaldehyde By Nano- TiO₂ Combined Coating

The real estate industry of our country developed rapidly, while people pursuing beauty and comfort of living,working environment, the furnitures and decoration materials became the indoor hidden trouble. Pollutant gas released by these materials deteriorated the indoor air quality seriously, between which the formaldehyde was listed as suspected carcinogen by World Health Organization (WHO) and American Environmental Protection(EPA). Therefore, developing and introducing non-pollution environmental materials was the great subject to be solved.Nanometer TiO₂ photocatalysis technology possessed many advantages: mild reaction conditions,rapid reaction rate, no secondary pollution and so on, which brought common concern of people, and considered as the most potential control technology used for environmental pollution. But it still existed two problems: the lower photocatalytic activity and the lower rate of sunlight utilization. TiO₂ in solution formed agglomeration state very easily, when adopted in coating immediately, the excellent performance of nanometer TiO₂ might be effected, and the coating might be chromatography, settling or caking. In order to overcome the two difficulties, the Nanometer TiO₂ was modified and dispersed, and then load on the coating to remove the indoor formaldehyde.In this paper, the pure TiO₂ powder, Zn-TiO₂ powder, N-TiO₂ powder, Zn/N/TiO₂ powder were made by sol-gel method, according to the most superior preparation parameter which our team obtained for a long time, according to the degradation of formaldehyde, the most superior doping ratio was screened and then characterized by X-ray diffraction (XRD). In order to solve the problems such as unstable dispersion, difficult to compound, the dispersion condition of modified nanometer TiO₂ in aqueous was discussed. The stability of aqueous suspension after adding modified nanometer TiO₂ was analyzed from different PH, different dispersant, different dispersant content, and different dispersion time; nanomaterials and coating were compounded by different crafts, the most superior craft was screened according to the degradation of formaldehyde, the degradation effected by nanometer TiO₂ addition was studied; whether the basic performance of traditional coating was changed after adding photocatalyst was judged through the performance examination.Last, L-F-H model was adopted to fit the kinetics with experimental data of formaldehyde degradation, the relation between reaction rate k and initial density of formaldehyde was discussed.The results indicated that:â‘ Zn-TiO₂, N-TiO₂, as well as Zn/N/TiO₂ could enhance photocatalysis performance remarkably, when the doping ratio n(Zn):n(N):n(TiO₂) =0.08%: 1%:1, the degradation of formaldehyde was the highest, the XRD characterization showed that the particle size of the Zn/N TiO₂ distributed uniformly, the average diameter was 19.8nm.â‘¡The modified nanometer TiO₂ was dispersed by physical dispersion and chemical dispersion, the result indicated that: when the addition of modified nanometer TiO₂ was 5%, dispersant A was 1%, pH value of the system was 7, the magnetic stirring time was 30min, the ultrasonic dispersing time was 1h, the dispersion effect was the best. Nanomaterials and coating were compounded by different crafts, the degradation of formaldehyde indicated that the second craft was better, that was, the modified nanometer TiO₂ aqueous was dispersed before adding into the coating , the firmness of the second craft was good as well. When nanometer TiO₂ was 3%, the formaldehyde degradation is the best. In order to simulate the visible light, the photocatalyst thin films was put under the incandescent lamp, after 2h, the formaldehyde degradation achieved to 36.36%. The basic performance examine of photocatalyst thin films showed as follows: barrier-free for several coating times, qualified film appearance, the 2H film hardness, water resistant, acid and alkali resistance.â‘¢The L-F-H kinetic model could excellently simulate the photocatalysis degradation of formaldehyde, the correlation between the kinetics model with experimental data was very high.Within the formaldehyde density scope(0.28～0.85 mg/m3), the reaction process accelerated with the increasing of formaldehyde density.