Study On Photocatalytic Activity And Immobilization Of Nitrogen And Iron Co-Doped Titanium Dioxide

In this dissertation, the basic principle about semiconductor photocatalysis was reviewed briefly at first. The resent research progress and the pending problems home and abroad in the area of photocatalysis were summarized in the detail. On this base, centering on improving the responsivity of photocatalysts to visible light and catalysts recovery, two kinds of immobilized photocatalysts were successfully synthesize by sol-gel method. Subsequently, the effects of synthesis condition and reaction condition on photocatalytic activity of compound photocatalysts have been systematically studied. The degradation mechanism and dynamics of as-prepared compound photocatalysts for organic target under simulant sunlight were amply analyzed. In this thesis, a series of important conclusions and valuable achievements with pratical application have been obtained, which have offered much experimental and theoretical guideline for the degradation of organic pollutants by using sunlight energy. This dissertation contains the following major parts:1. The compound photocatalysts N and Fe³⁺-codoped TiO₂ supported on artificial zeolite(AZ), was synthesised by sol-gel method. The effects of calcining temperature, supports granularity and loading times on the performance and structure of the Fe³⁺/N/TiO₂/AZ were investigated, and the best preparation condition under simulant sunlight was obtained. The analysis results indicated that the nanosized Fe³⁺/N/TiO₂ with anatase crystallization uniformly covered on the supports' surface, and the compound photocatalyst with medium pore, has the same granular distribution with the suppors AZ. Moreover, the addition of N and Fe³⁺ makes the synergetic effects, which shifted the absorption regions of TiO₂ to visible light and enhanced the quantum efficiency. Further, the loading effects of artificial zeolite increased the activity of the photocatalysts.2. Using active carbon (AC) as the supports, the compound photocatalysts Fe³⁺/N/TiO₂/AZ was synthesised by sol-gel method. Based on the previous experiments, we simplified some common parts,emphasized the characteristic of AC,and the the effects of synthesis condition were studied.Different from the zeolite,temperture not only have effect on catalysts'structure and N-doped amount,but also on the structure of AC.The results indicated that the compounded photocatalyst using prepared sol-solution, calcined by a novel calcination method,supported on 60-80 mesh sized AC,loading 3 times,has single anatase crystallization,smaller crystal size(15.34nm),and shows the strongest response to visible light.3.The repeated utilization experiments of the two compound photocatalysts shows that AC has the better prospect and performance than AZ as the supports.At the fourth recycle using of N/Fe³⁺/TiO₂-AC,the degradation rate of dye decreased by 15% compared to the initial rate,continuing recycle use,the degradation rate kept at 82%. While the degradation rate of N/Fe³⁺/TiO₂-AC photocatalyst only has 72%during its 5th times recycle use.The photocatalytic performance decreasing of compound photocatalysts are rusulted from the shedding of N/Fe³⁺/TiO₂ from the surface of supports, and also have something with preparation technology and characteristic of supports.4.The results of compared experiments between different kinds of photocatalysts indicated that,compared with N and Fe co-doped TiO₂ powder catalyst,the immoblized catalyst showed higher photocatalytic activity.This may due to the synergetic effects between supports'adsorption capacity and photocatalytic activity of catalyst.From the CODcr removed experiment,we can see that the compound photocatalysts have less mineralization ability to dye solution,compared with its high decoloration rate.The research results indicated that the addition of N and Fe³⁺ makes the synergetic effects,which shifted the absorption regions of TiO₂ to visible light,and enhanced the UV absorption.And the introduction of sopports AZ and AC,realized the recovery and recycle of TiO₂ powder.But the lower efficiency to sunlight and lower repeat times, restricted the industrialization of compound photocatalyst.