Preparation And Properties Of Visible Light Active TiO₂/Diatomite Composite Photocatalyst

Titanium dioxide is a kind of excellent photocatalyst,but it is easy to aggregate,difficult to recycle and do not respond visible light in practical application,these problems can be effectively solve through loading,element doping.In this paper,Titanium sulfate was used as the titanium source,diatomite was used as the carrier.Titanium dioxide was supported on diatomite via hydrolysis precipitation method.The synthesis and calcination process of precursor were investigated and optimized.The visible light active N-doped composite photocatalyst was prepared by ammonia atmosphere calcination method,and the effect of the calcination process were explored.The results show that the nanocrystalline titanium dioxide is loaded into the surface and the pores of the diatomite in the form of anatase phase in the composite photocatalytic material.After calcination,the titanium dioxide particles react with the surface of diatomite and form a strong Si-O-Ti bond.When the loading of titanium dioxide was 60%,the concentration of titanyl sulfate was 0.4 mol·L^-1,the concentration of ammonia was 13%,the reaction temperature was 0℃,the calcination temperature was 600℃,and the calcination and holding time was 3 h,the composite photocatalytic material shows a better photocatalytic performance.Aiming at tetracycline hydrochloride degradation,The concerntration of tetracycline hydrochloride was 50 mg·L^-1,the amount of catalyst was 2.4 g·L^-1,and the initial p H was 3 shows a better photocatalytic performance.N-doped TiO₂/diatomite composite photocatalyst prepared by the calcination of ammonia atmosphere has photocatalytic activity under visible light.The band gap of the composite photocatalyst after calcination at 500℃has been reduced to 2.70 e V.With the increase of the calcination temperature and the calcination time,the N-doping effect is improved and the forbidden band width is decreasing.However,with the increase of N-doping effect,the resulting defects also lead to the formation of ineffective recombination centers,which inhibit the photocatalytic activity.When the calcination temperature is 500℃and the calcination temperature is 4 h,the prepared N-doped composite photocatalytic material has the best performance under visible light.Aiming at tetracycline hydrochloride degradation,The concerntration of tetracycline hydrochloride was 20 mg·L^-1,the amount of catalyst was 1.0 g·L^-1,and the initial p H was 5 shows a better photocatalytic performance.Composite photocatalyst formed a gap N doping after ammonia atmosphere calcined,resulting in a visible light response.The radicals produced by TiO₂/diatomite composite photocatalyst are mainly composed of hydroxyl radicals under ultraviolet light.The radicals produced by N-doped composite photocatalysts are mainly composed of superoxide radicals under visible light.During the photocatalytic reaction,tetracycline hydrochloride has undergone ring-opening reaction,and the intermediate products with smaller formula weight have been formed.The degradation process of tetracycline hydrochloride in UV and visible light is similar,but the degradation rate is faster under ultraviolet light.