| Rice husk(RH) is a kind of biomass resource with the feature of rich contents of silicon and carbon. In this paper, based on the special composition of RH, compound photocatalysts with visible light excitation of TiO2/SiO2 loaded on pyrolystic carbon(TiO2/SiO2/PyC) and TiO2/SiO2 loaded on activated carbon(TiO2/SiO2/AC) were prepared by pyrolysis-activation and pyrolysis method separately after loading TiO2-sol on surface of RH. The structure was characterized by X-ray diffraction(XRD), Fourier transform infared (FTIR) and scanning electron micrioscopy(SEM), photocatalytic activity was evaluated by the photo-catalyzing degrading reactivity of methylene blue(MB) for photocatalyst and UV-Vis.RH-TiO2 gel precursor was synthesized by in-site coating with Ti(OBu)4(TBOT), then it was pyrolyzed and calcined in nitrogen(N2) atmosphere, for obtaining photocatalyst of TiO2/SiO2/PyC with performance of excitated by visible light, and influences of amount of TBOT in precursor, pyrolytic time and temperatures on stucture and photocatalytic activity were discussed. It was indicated that a supported structure of shell-nuclear existed in TiO2/SiO2/PyC, the nuclear was composed of pyrolystic carbon-SiO2, shell was composed of TiO2 and SiO2, and the bonds of Ti-O-Si were formed between TiO2 and SiO2 on surfaces of shell-nuclear and contecting surfaces of TiO2 and SiO2. It was indicated by XRD that phase conversion temperature and growth of crystallite of loaded TiO2 was obviously inhibited,the sample kept anatase even pyrolyzed at 700℃, and absorption strength of UV-Vis light was enhanced with a greater degree, photocatalytic activity of photo-catalyzing degrading MB under visible light was also improved obviously.The performance of 2-TiO2/SiO2/PyC-4-500 was best of all.Preparation of TiO2/SiO2/AC photocatalyst with good visible light excitation was successfully achieved by pyrolysis-activation method activated with KOH in N2 atmosphere,using precursors prepared by in-site coating, hierarchical coating, liquid deposition coating as materials, and influences of preparation methods of precursors,the mass ratio of alkali and carbon, calcination temperature on structure were discussed, meanwhile, performances of TiO2/SiO2/AC were compared with that of nano TiO2 and TiO2/SiO2 as well. It was showed of enhanced absorption in UV-Vis region, increased specific surface area(SBET) and enhanced thermal stability conformed by keeping anatase after calcinced at 700℃. A supported structure of shell-nuclear also existed in TiO2/SiO2/AC, the nuclear was composed of activated carbon-SiO2, shell was composed of TiO2 amd SiO2, and the bonds of Ti-O-Si were formed on surfaces of shell-nuclear and contect surfaces of TiO2 and SiO2.Degradation ratio of MB on the photocatalysts was increased obviously. TiO2/SiO2/AC1-2-500 prepared with precursor synthesized by in-site coating showed best photocatalystic activity, even better than that of 2-TiO2/SiO2/PyC-4-500 prepared by pyrolysis method.The pyrolysis-activation conditions of TiO2/SiO2/AC1-2-500,using precursor synthesized by in-site coating in condition of TBOT of 2.0ml, were showed: pyrolystic temperature was 500℃and time was 4 h, the mass ratio of alkali and carbon was 2, activated at 600℃for 1 h, calcined at 500℃for 3 h. The degradation of methylene blue on TiO2/SiO2/AC1-2-500 photocatalyst reached 72.51%, the main diemeters of pores were 4 nm and 50 nm, the adsorption curve could be classified as II adsorption, SBET reached 608.4 m2/g。In systems of TiO2/SiO2/PyC and TiO2/SiO2/AC photocatalysts, there is certain synergy between TiO2 and compound supports, which promtes photocatalystic activity of TiO2. |
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