Papers by Keyword: Photocatalytic

Abstract: Nanocrystalline W-doped TiO₂ powders with different initial W/Ti ratio in starting materials have been prepared by hydrothermal method. The phase composition, morphologies, specific surface areas and the photocatalytic activities under visible light irradiation of the synthesized powders have been characterized. XRD identification reveals that the synthesized powders were composed of anatase. No rutile has been detected in the products. The specific surface area of the powders was ranged from 185 to 210 m²/g by BET measurement. The averaged grain size of the powders was calculated as about 12 nm by Scheller's method. Uniform size distribution and good crystallinity have been confirmed by TEM. UV-Vis spectra show that the absorption edges of the synthesized W-doped TiO₂ powders with different nominal doping concentration of W ions have been red-shifted into visible light region, which suggests that the W ions have been doped into the lattice of TiO₂. In our case, W-doped TiO₂ with initial W/Ti atomic ratio of 1% in starting materials has the best photocatalytic activities when decompose the Methylblue in its aqueous solution, which is consistent with that of the theoretical results from our previous work.

Abstract: Using TiCl4 as the titanium source, urea as the precipitating agent, nano-TiO2/fly ash beads composite materials were prepared by hydrolysis-precipitation method. The materials were characterized by SEM and XRD methods. SEM observation shows that the surface of beads have been loaded a uniform TiO2 film. XRD results shows that TiO2 films have the main phases of anatase and rutile mixed crystal structure. The effect of surface activation process of fly ash beads on TiCl4 solution hydrolysis rate was studied. The influence of calcination temperature on the microstructure and properties of composite materials was also discussed. The photocatalytic properties of the prepared materials was measured by using UV-1800 uv-vis spectrophotometer. The results show that: The composite which calcined at 500°C has a grain size of 15nm, anatase phase content of 90%, shows the best photocatalytic effect. The degradation rate of methyl orange solution can reach 95% after 2 hours irradiation (300W, Mercury lamp). Repeated experiments show that the degradation rate of composite materials still reach 80% after being used for 5 times .

Abstract: Nano-ZnO, nano-TiO₂ and their mixed catalyst respectively degrade methyl orange solution with concentration 10mg/L in sunlight. When the dosing quantity is 1g/L during 8h degradation, the degradation effect is better and the degradation rates of three catalysts can all reach more than 93% with prolonging of degradation time, and the degradation effect of mixed catalyst is best and its degradation rate reaches more than 99%. Moreover the effect of TiO₂ content in the mixed catalyst on catalytic degradation isn’t distinct.

Abstract: The inactivation of chlorella was studied using a circular device of photocatalytic reaction with TiO₂/foam nickel as catalysts. Parameters such as reactor configuration, reaction time and pH of chlorella affecting the degradation rate of chlorella were studied. The results showed that photocatalysis with TiO₂/foam nickel was an effective process for the inactivation of chlorella. After photocatalytic reaction for 10h, the degradation rate was more than 97.75%. With reaction time increased, the removal of chlorella increased gradually.

Abstract: In the present study, design of experiments (Orthogonal experiment) was used to find an optimal combination for the factors, which affect the catalytic activity of nano-crystalline TiO₂ powder synthesized by sol–gel method. Sixteen kinds of TiO₂ powder were prepared by changing three material ratio at four levels. The effects of calcinations temperature on the catalyst activity of TiO₂ were investigated by single factor experiments. TiO₂ were characterized by XRD. The results of design of experiments are examined by the direct observation analysis. The preparation conditions have been optimized as material ratio nTi(OC₄H₉)₄: nH₂O: nHN(C₂H₅OH)₂: nC₂H₅OH=1:2:2.5:20, mean 16.8 nm TiO₂ nanoparticle with anatase structure obtained at 500°C calcination. The photodegradation efficiency of methylene blue in aqueous solution is 99 % under 1g/L catalyst.

Abstract: Precursor In(OH)₃ was synthesized by ultrasonic method with carbamide and indium salt, and was performed microwave radiation, then nano amorphous In₂O₃ was obtained. The structural and morphology of precursor and In₂O₃ were characterized by TG-DTA, XRD, TEM, etc. The results show that the In₂O₃ is nano amorphous with average grain size 12nm by microwave method. This paper discovered that nano amorphous In₂O₃ has good photocatalysis when we used it to degrade acidic black dye.

Abstract: Porous TiO2 films were prepared through dip-coating on glass substrates using different molecular weight of PEG. Surface roughness increased with increasing PEG molecular weight. The film prepared with PEG400 was fairly smooth with slight roughness. The films prepared with high molecular PEG became rougher and there were some larger particles on the films. When the PEG molecular weight got higher, adsorption edge of the films tended to move toward shorter wavelength region. In the wavelength range between 350 and 450 nm, larger PEG molecules made higher film transmittance. The particles prepared using higher or lower molecular weight of PEG had less surface area than using PEG1000. The average pore sizes were 14 nm, 15 nm, 28 nm, and 52 nm, and the total pore volume were 0.12 ml/g, 0.13 ml/g, 0.08 ml/g, and 0.09 ml/g for the TiO2 powders prepared using PEG400 to PEG 6000.

Abstract: TiO2 film was dip-coated on glass substrate by a sol-gel process. Ti(OC4H9)4 was used as the titanium source. Surface morphology, crystallite phase, UV-Vis transmittance spectrum and pore size distribution of TiO2 powder prepared under the same conditions of the film were investigated. Surface of TiO2 film is fairly smooth with very slight roughness. No obvious hole or pore is found on the surface of the film. The strongest diffraction peak situated at 2θ=25.3o is the characteristic of anatase TiO2. The absorption edge of the TiO2 film is around 350 nm, while the transmittance fluctuates between 50% and 90%. The average pore size of the TiO2 particles calculated by BJH method is 23 nm. The total pore volume and specific surface area are 0.16 ml/g and 27 m2/g, respectively.

Abstract: The composite film, FeW11O399-(FeW11)/TiO2/ SiO2, was prepared by liquid phase deposition method (LPD) at low processing temperature for the first time. Formation of the stable composite film is due to strong chemical reaction of ≡Ti-OH from TiO2/SiO2 with the surface oxygen atoms at vacant sites of FeW11. The structural properties of the film were characterized using FT-IR、UV-vis spectra, Elemental Analysis. The experimental results confirmed the retention of the primary Keggin structure and the saturation of the surface of the lacunary FeW11; Formation of Ti–O–Si bond implies that the TiO2 crystallites highly dispersed on the silica surface via oxygen as a bridge. The catalytic activity was tested by the photo-degradation of aqueous azo dye congo red (CR) (0-20 mmol•L-1). The resulting film exhibited efficient visible-light photocatalytic activity to decompose aqueous azo dye CR，which is mainly attributed to long time existence of Fenton-assisted FeW11/TiO2/SiO2 excitation state. According to the experimental results, a synergistic effect mechanism of the photodegradation process is proposed.

Abstract: Fe-doped anatase TiO₂ nanobelts were prepared using layered titanate nanobelts as precursor by two-step hydrothermal process. Various measurement techniques were employed to investigate the morphology and structure of products. The results show that Fe-doped TiO₂ still remain nanobelt-like and structure as pure TiO₂ nanobelts. Fe-cations doped in TiO₂ nanobelts lead to the red-shift of the absorption edge of TiO₂ nanobelts. The visible-light photodegradation of Rhodamine B on the products exhibits that Fe-doped products with low Fe-content show higher photocatalytic activity than that of TiO₂ nanobelts or Fe-doped product with high Fe-content.