| The treatment of dyeing and printing wastewater has been one of key topics in our country and even in the world. Wastewater treatment techniques mainly include physical method, chemical method, physical and chemical combination method, biochemistry method and so on. With the development of science and technology, the variety of dyes shows an increasing tendency, their component is becoming complex, and the wastewater of many dyes has the characteristic of oxidation resistance, anti-photolysis, high color degree and high concentration. So these lead to the high requires for the techniques of wastewater treatment. Compared with the traditional printing and dyeing wastewater treatment method, semiconductor photocatalytic technology has attracted wide attention for its wild reaction conditions, strong oxidation ability, can use solar energy as energy source, and photocatalyst doesn’t consume, no secondary pollution, non-toxic, stable in reaction process.Titanium dioxide(Ti O2) nonmaterial has attracted significant attention in the last decades and has been intensively studied due to its biological and chemical inertness, and their promising properties. Nevertheless, along with these properties, Ti O2 does have some drawbacks such as; Ti O2 mainly absorbs ultraviolet light(UV) with wavelengths <380 nm, which represents only 5% of the solar spectrum. This disadvantage limits its application for environmental remediation with solar light and O2. Doping Ti O2 with nonmetals and deposition transition metals ions can improve the efficiency of Ti O2 photo catalysis, and to develop a visible light photocatalyst. In this work, the synthesis and characterization of doping Ti O2 with metals/non-metals and their application in dye degradation were investigated as following:(1) C-Ti O2 thin films were synthesized by a modified sol–gel route based on the selfassembly technique exploiting Tween 80(T80) as a pore directing agent and carbon source. The effect of calcination time on the photocatalytic activity of C-doped Ti O2 catalyst was studied. The samples were characterized by X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), Fourier transforms infrared(FTIR), UV-vis diffuse reflectance spectroscopy, and photoluminescence spectra(PL). The XRD results showed that C-Ti O2 sample calcined at 400 ?C for various times exhibited anatase phase and no other crystal phase was identified. C-Ti O2 exhibited a shift in an absorption edge of samples in the visible region than that of conventional or reference Ti O2. The XPS results showed an existence of C in the Ti O2 catalysts and C might be existed as C-O-Ti group. Moreover, the C-Ti O2 thin film calcined at 400 ?C for 30 min showed the lowest PL intensity due to a decrease in the recombination rate of photogenerated electrons and holes under UV light irradiation. Also the photocatalytic activity of synthesized catalyst was evaluated by decomposition of methyl orange(MO) under visible light irradiation. The results showed that the optimum preparations of C-Ti O2 thin films were found to be under calcination temperature of 400 ?C, calcination time of 30 min, and with preparation 9 layers film. And the photodegradation percentages were found to be 29.75 and 91.89 % for Ti O2 and C-Ti O2, respectively.(2) Fe2O3/Ti O2 nanoparticle was successfully prepared by sol-gel method and characterized by XRD, FT-IR, UV-vis absorption spectroscopy, PL, and porosimetry analysis. The characterization showed the presence of nano-sized Fe2O3 particles on the Ti O2 support. The Fe2O3/Ti O2 nanoparticle exhibited enhanced absorption in the broad visible-light region together with an apparent red shift in the optical absorption edge. The effect of Fe2O3 content, calcination temperature and calcination time on the photocatalytic efficiency of the catalysts was examined on methyl orange degradation. The results showed that the optimum catalyst preparation process: calcination temperature 500?C, calcination time 3 h, with(10 wt. %) Fe2O3. More addition, the efficiency of methyl orange degradation by Fe2O3/Ti O2 nanoparticle was more than two times higher than that of control in the presence of H2O2, which should be attributed to the heterogeneous photoFenton process. All these results indicate the possibility of the practical application of this photocatalyst for water treatment.(3) CN-Ti O2 was modified with cryptomelane octahedral molecular sieves(OMS-2) by the sol-gel method based on the self-assembly technique to enhance its photocatalytic activity under the daylight irradiation. The synthesized samples were characterized by XRD, UV-vis spectroscopy, FT-IR and porosimeter analysis. The results showed that the addition of OMS-2 in the sol lead to higher Brunauer-Emmett-Teller(BET) surface area, pore volume, porosity of particle after heat treatment and the specific surface area, porosity, crystallite size and pore size distribution could be controlled by adjusting the calcination temperature. Compared to the CNTi O2-400 sample, CN-Ti O2/OMS-2-400 exhibited greater red shift in absorption edge of samples in visible region due to the OMS-2 coated. The enhancement of photocatalytic activity of CNTi O2/OMS-2 composite photocatalyst was subsequently evaluated for the degradation of methyl orange under the daylight irradiation in water. The results showed that methyl orange degradationrate reach to 37.8% for the CN-Ti O2/OMS-2-400 sample under the daylight irradiation for 5 h, which was higher than that of reference sample. The enhancement in daylight photocatalytic activities of the CN-Ti O2/OMS samples could be attributed to the synergistic effects of OMS-2 coated, larger surface area and red shift in adsorption edge of the prepared sample.(4) To remove the disadvantages of nonmetal element doping, silver was use to synthesis the Ag/C-Ti O2 nanoparticles by a modified sol–gel methods based on the selfassembly technique exploiting Tween 80(T80) as a pore directing agent and carbon source and sliver nitrate(Ag NO3) as a source of silver. The effect of silver concentration on the photocatalytic activity of Ag/C-Ti O2 catalyst was studied. The samples were characterized by UV–vis diffuse reflectance spectroscopy, and PL spectra. The Ag/CTi O2 exhibited a shift in an absorption edge of samples in the visible region than that sample without silver(C-Ti O2). Moreover, the sample of 5 wt% Ag/C-Ti O2 showed the lowest PL intensity due to a decrease in the recombination rate of photogenerated electrons and holes under UV light irradiation. Also the degradation of methyl orange dye under visible light irradiation was performed to evaluate and compare the visible-light photocatalytic activity of the Ag/C-Ti O2 samples and reference. The results showed that the 5 wt% Ag/C-Ti O2 sample exhibited the best photodegradation rate among others samples. |
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