| Photocatalytic oxidation technology is one of the main methods to remove water pollutants,which can effectively coordinate the conflict between economic development and environmental protection.The selection of photocatalyst is the core of photocatalytic technology,among the photocatalysts,Ti O2 has the advantages of non-toxic,low cost and stable performance.However,it only has the ability to respond to ultraviolet light,and the response ability to visible light is weak.In addition,the application of Ti O2 is limited due to its easy agglomeration,poor adsorption capacity and high electron-hole recombination rate.Therefore,the preparation of composite materials to improve the performance of Ti O2 is of great significance to promote the application of Ti O2 materials in the field of water treatment and environmental protection.In recent years,Metal Organic Frameworks(MOFs)have been used in the field of photocatalysis because of their unique structure and performance advantages.Therefore,this paper combined anatase phase Ti O2 with MOFs materials with stable structure and rich pores to improve the enrichment ability of Ti O2-based catalyst for pollutant molecules and promotes the separation of photogenerated electron holes.The Ti O2/MOFs composite photocatalyst shows excellent photocatalytic oxidation performance and the mechanism of photocatalysis was explored.The main research results of this work are shown below:(1)Ti O2 nanoparticles were prepared by hydrothermal method using tetra-butyl titanate as titanium source.Different crystal types of Ti O2 were obtained by changing the calcination temperature.Then,Ti O2/Ui O-66(UT)composites with different composite proportions were prepared by simple ultrasonic assembly-solvent evaporation method,and the composites were investigated in detail by XRD,XPS,UV-vis diffuse reflectance spectroscopy and fluorescence emission spectroscopy(PL).It is observed by SEM that Ti O2 is dispersed on the surface of Ui O-66 octahedron,which is more favorable for the active site to be exposed to the outer surface of the catalyst.The BET results show that the specific surface area of UT composite is up to 205.65 m2/g,which is 4 times that of Ti O2,which greatly improves the adsorption capacity of the catalyst.Under UV irradiation,the anatase phase Ti O2 has the best photocatalytic degradation efficiency of Rhodamine B(Rh B)among different Ti O2 monomers.Moreover,in different proportions of the complex,UT30/100 has the best catalytic performance under ultraviolet light,with a degradation efficiency of 99.1%for Rhodamine B(Rh B)in 60 min.The UT30/100 still retains its intact structure after 5 cycles.This is because Ui O-66 material has rich pores and stable structure.Ti O2 is loaded on Ui O-66,and adsorption-photocatalysis synergy is formed,which makes it have excellent photocatalytic degradation performance and cycle life.(2)NH2-MIL-125 was synthesized from isopropyl titanate as titanium source and2-amino-teraphthalic acid as ligand.The Ti O2/NH2-MIL-125(NMT)composite was prepared by combining it with Ti O2.The effects of different composite proportions and the amount of catalyst on photocatalytic degradation of Rh B were studied.UV-Vis diffuse reflectance spectra showed that the introduction of-NH2 could effectively extend the photo response range of the catalyst to visible light region.TEM confirmed that the agglomeration of Ti O2 is significantly improved.Under visible light irradiation,the catalytic degradation efficiency of NMT composite for Rh B is 6.6 times that of Ti O2.In addition to the efficient adsorption performance of NMT composite,this result is also attributed to the effective separation of photogenerated electrons and holes,which is confirmed by PL spectrum and transient photocurrent test results.In addition,hydroxyl radical(·OH)is found to be the main reactive substance in the NMT photocatalytic system through radical capture experiments.The band conduction potential of the catalyst is obtained according to the Mott-Schottky curve.Moreover,the source of·OH in the catalytic system is explored and the Z-scheme electron transfer mechanism of NMT composite material is analyzed. |
PDF Full Text Request