| In recent years, photocatalytic technology has become a wastewater treatment method which has broad application prospects, and gradually become the focus of extensive research. Ti O2 photocatalyst has more researched and applicated for now, with strong photocatalytic ability, good stability, non-toxic and pollution-free, and other multiple advantages. Since the wider band gap of Ti O2 is 3.2ev, its light absorption is limited to the ultraviolet region, which is unable to make full use of sunlight. While the band gap of Fe2O3 was from 1.9ev to 2.2ev, it can make better use of solar energy, but its light absorption efficiency is low. Therefore, in view of the advantages and disadvantages of the two materials, we prepared the composites of Fe2O3 and Ti O2 through compound-semiconductor. The composites extended the light absorption range of photocatalytic material, and improved the light absorption efficiency or the rate of charge separation, thereby improving the optical absorption properties and catalytic efficiency of photocatalyst. Based on this point, the main work and study results of the paper are as follows:1.This paper was referred to the method of literature, with Fe Cl3 as Fe3+ source, at different ratios of nFe/nTi and NO3-、SO42-、Cl-、PO43- and other different anions media, let Fe3+ salt and carbonate co-hydrolysis under boiling reflux, produced the Fe2O3-Ti O2 composites. XRD, TEM, UV-Vis DRS and PL spectra and other characterization methods were used to compare the effects of nFe/nTi ratios and different anions on the product morphology, structure and optical properties. Naphthol blue black(NBB) as the model pollutant, the effects of the nFe/nTi ratios and different anions on Fe2O3-Ti O2 photocatalytic activity were compared and studied by kinetic evaluation. Finally, with the results of the literature, preliminary explored the impact on product photocatalysis mechanism of different amounts of Fe3+ doped or composite.2. Firstly, titanate precursor was synthesized by alkali Hydrothermal Method 24 h,,which showed elongated tubular one-dimensional nanomaterials titanate. After heat treatment, titanate transformed into anatase Ti O2 pure single crystal phase, morphology remained unchanged. The hydrothermal synthesis was prolonged to 48 h, the Ti O2 was showed irregular flaky particles and the absorption edge blue shift, its porous structure was destroyed. Different nFe/nTi ratios of Fe2O3-Ti O2 were dispersed nanocrystalline particles coated-type state, with the increasing of nFe/nTi ratios, the particle size and the dispersion was one of the important factors, which influences its photo-catalytic activity. In NO3-、PO43-and Cl-medium Fe2O3-Ti O2 was dispersed particles coated type nanocrystalline state, when in HCl/Fe Cl3 medium, dispersion is preferably. In SO42-medium, when nFe/nTi was 0.3, the product was appeared numerous slender titanate nanotubes, some of Ti O2 particles attached and mounted on the tube.3. Ti O2 photocatalytic activity of different hydrothermal time is: Ti O2(24h)>Ti O2(48h). Fe2O3-Ti O2 photocatalytic activity of different nFe/nTi ratios is: Fe2O3-Ti O2(0.1)>Fe2O3-Ti O2(0.3)>Fe2O3-Ti O2(0.7)>Fe2O3-Ti O2(0.5)>Ti O2>Fe2O3-T i O2(0.05), indicating that when nFe/nTi was 0.05, Fe2O3 composite inhibited the photocatalytic activity of Ti O2, but with the increasing amount of Fe2O3, Fe2O3-Ti O2 adsorption properties and photocatalytic activity were superior to Ti O2, when nFe/nTi = 0.1 was best.4. In different medium, doping different nFe/nTi Fe2O3 ratio of Ti O2, the photocatalytic activity to the degradation of NBB plays a different role. In NO3-, SO42-, Cl- medium, the composition of Fe2O3 can improve adsorption and photocatalytic activity of Ti O2; in PO43- medium, the composition of Fe2O3 shows significant inhibition to photocatalytic activity of Ti O2. The reason probably is that when Fe3 + is in the hydrolytic polymerization, some PO43- is wrapped in them, so that ferric salt cannot be converted to nuclei. When nFe/nTi was 0.1, the order of the Fe2O3-Ti O2 photo-catalytic activity in NO3-, SO42-, Cl-, PO43-medium was, Fe2O3-Ti O2(Cl-)>Fe2O3-Ti O2(SO42-)>Fe2O3-Ti O2(NO3-)>Ti O2>Fe2O3-Ti O2(PO43-). When nFe/nTi was 0.3, the order of the Fe2O3-Ti O2 photo-catalytic activity in the negative ion medium was, Fe2O3-Ti O2(SO42-)>Fe2O3-Ti O2(Cl-)>Fe2O3-Ti O2(NO3-)>Ti O2>Fe2O3-Ti O2(PO43-).5. The photocatalytic activity of the product was characterized by DRS and PL, the results were summarized as follows: In the HNO3/Fe(NO3)3 medium and the H2SO4/Fe2(SO4)3 medium, after doping the Fe2O3, the absorption of light of the Fe2O3-Ti O2 changed greatly. The red shift of band edge was appeared and the intensity of the optical absorption was elevated. Meanwhile Ti O2’s band gap energy was decrease, which was increased the rate of light utilization of Fe2O3-Ti O2 and promoted the light catalytic reaction. Under this condition, the change of Fe2O3-Ti O2 photocatalytic activity and the intensity change of the PL spectral peaks were negatively correlated. In the H3PO4/Fe Cl3 medium, the composition of the Fe2O3 reduced the absorption to light of Ti O2, so that light catalytic activity of Ti O2 was inhibited. So the change of Fe2O3-Ti O2 photocatalytic activity and the intensity change of the PL spectral peaks were positively correlated.6. The photocatalytic reaction mechanism of Fe2O3-Ti O2 nanoparticles preliminarily was investigated. When the doping amount of Fe2O3 less or overdose, it was caused the electron-hole pair separation, and result in the decrease of Fe2O3-Ti O2 photocatalytic activity. When the doping amount of Fe2O3 nFe/nTi was 0.1, the photocatalytic activity was the best, it was because that the doping of Fe3+ in Ti O2 lattice can generate defects on its surface, which become light-generated electron-hole pairs shallow potential capture hydrazine. Thereby it prolongs the time of electrons and holes recombination and reduces the rate of light-generated electron-hole recombination, and so the quantum efficiency of Ti O2 was increased. |
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