Preparation And Photocatalytic Properties Of TiO₂/Molecular Sieves Co-Doped With Manganese And Nitrogen

TiO₂ semiconductor materials have attracted much attention in the field of environmental protection and photocatalysis because of their high photocatalytic activity,low cost and easy availability.However,TiO₂ photocatalysts have limited range of absorption of light source,easy generation of photogenerated carriers,poor adsorption performance and difficulty in recycling.In this thesis,TiO₂/5A zeolite molecular sieve composites were synthesized by sol-gel method using 5A zeolite molecular sieve as carrier.The single element doping and co-doping modification of manganese and nitrogen were carried out to reduce the photogenerated electron-hole of TiO₂.The composites probability increases the visible light catalytic activity and achieves reusable purposes,broadening its application range.By controlling the TiO₂ loading of TiO₂/5A zeolite molecular sieve composites,the photocatalytic degradation efficiency was optimized and its crystal phase structure,element composition,shape and photocatalytic activity were characterized by XRD,XPS,FTIR,SEM-EDS,UV-vis and PL.The results show that when the loading of TiO₂was 20%,the degradation efficiency of malachite green is 92%within 80 min under visible light irradiation,which has excellent photocatalytic performance.The specific surface area and thermal stability of the sample after loading were significantly increased.Under visible light irradiation,the degradation efficiency of TiO₂/5A zeolite molecular sieve composites to malachite green was significantly higher than that of pure TiO₂ powder and pure 5A zeolite molecular sieve,which was mainly due to the photocatalytic degradation of TiO₂/5A zeolite molecular sieve composites.Synergistic with the adsorption properties of the carrier to obtain higher photocatalytic activity.In order to make better use of sunlight and reduce the recombination probability of photogenerated electron-holes,the visible light catalytic activity of TiO₂/5A zeolite molecular sieve composites was improved,and ion doping modification was further carried out.The results show that the TiO₂/5A zeolite molecular composites with manganese and nitrogen have higher photocatalytic activity than the single element doping.When manganese and nitrogen were co-doped with TiO₂,the molar percentage of manganese and titanium was n?Mn?:n?Ti?=0.5%,the molar percentage of nitrogen and titanium was n?N?:n?Ti?=10%,the degradation efficiency of malachite green is97%within 60 min under visible light irradiation.The degradation efficiency was the highest,mainly because manganese ions can inhibit the photo-generated carrier recombination,and nitrogen doping can broaden the photo-response range of TiO₂,thus obtaining higher visible light photocatalytic activity.In addition,after five cycles of manganese and nitrogen co-doped TiO₂/5A zeolite molecular sieve composites,the degradation efficiency of malachite green remained above 88%,indicating that it has good catalytic cycle stability.