Study On Natural Light-Catalyzed Formaldehyde And Humidity Control Materials

Indoor air environment includes indoor air hot and humid environment and indoor air quality,which affects the health and comfort of residents.Formaldehyde is one of the gases that lead to bad indoor air quality,and unsuitable temperature and humidity environment leads to bad indoor temperature and humidity environment.It will play an important role in improving the indoor air temperature and humidity.In this study,the natural light-catalyzed formaldehyde and humidity control materials was prepared by doping with N-source modified TiO₂,and using clay minerals such as diatomite and sepiolite with large specific surface area,porosity and strong adsorption as the carrier of g-C₃N₄-TiO₂.In this study,g-C₃N₄-TiO₂photocatalyst with heterogeneous structure was synthesized by calcination method,and then combined with Sphagnum/diatomite based and sphagnum/Sepiolite based humidity control materials to prepare natural light driven photocatalytic humidity control materials.The effect of formaldehyde degradation and humidity control was studied by the measured data of laboratory test.X-ray diffraction（XRD）,energy dispersive spectrometer（EDS）,environmental scanning electron microscope（ESEM）,ultraviolet visible spectrophotometer（UV VIS）and Fourier transform infrared spectroscopy（FTIR）were used to study the photocatalytic degradation of formaldehyde and the mechanism of temperature and humidity regulation.The results are as follows:（1）（1）The heterostructure g-C₃N₄-TiO₂photocatalyst is synthesized by doping N-source modified TiO₂,so that the absorption edge of the photocatalyst is red-shifted,extended to the visible light region,and the band gap is reduced.（2）The NT-5 photocatalyst prepared by using the mass ratio of urea and TiO₂at5:1 and calcining at 520℃,under natural light,the effect of degrading formaldehyde and adjusting temperature and humidity of NT-5 supported on sphagnum/diatomite is the best;The NT-3 photocatalyst prepared by using the mass ratio of urea and TiO₂at a temperature of 3:1 and calcining at a temperature of 520℃has the best effect on the degradation of formaldehyde and temperature and humidity regulation of NT-3supported on sphagnum/sepiolite under natural light.The modified photocatalyst supported by porous minerals of diatomite and sepiolite can generate more Bronsted acid sites,provide reaction sites for the degradation of formaldehyde,and improve the efficiency of formaldehyde catalysis.（3）The results of XRD,ESEMM-EDS and FTIR show that the urea doped with TiO₂can form a new material g-C₃N₄,which can be combined with TiO₂to form g-C₃N₄-TiO₂.The size of calcined TiO₂becomes larger,from 6.29nm to 14.13nm,and the crystallinity becomes stronger.In the micro ESEM diagram,g-C₃N₄-TiO₂has good separation on either Sphagnum/diatomite or sphagnum/sepiolite.（4）The results show that the band gap of pure TiO₂is 3.31ev,while that of NT-3and NT-5 are 3.11ev and 3.09ev,respectively.The reason is that g-C₃N₄and TiO₂form a type II heterojunction,the electrons in the conduction band of g-C₃N₄will transfer to TiO₂through the heterojunction,and the holes（h⁺）in the valence band of TiO₂will transfer to the valence band of g-C₃N₄-TiO₂.The narrow band gap of g-C₃N₄-TiO₂is due to the charge transfer.（5）The results showed that NTD-5 composite could effectively control the formaldehyde concentration and relative humidity in the test chamber at about0.1mg/m³and 60%RH respectively under natural light,due to the synergistic effect of photocatalysis and adsorption.Sphagnum/sepiolite can also effectively control the indoor formaldehyde concentration at 0.2mg/m³,stabilize the indoor relative humidity at about 50%～58%RH,and have the effect of adjusting the indoor temperature at 0.9℃.