Eco-Materials Processing and Design IX

Abstract: Nano-sized nitrogen-doped Ti-W mixed oxides (N-TiO2-x%WO3) were prepared by soft chemical method, and their intrinsic characteristics were investigated using XRD, TEM, N2 adsorption and desorption isotherms, UV-Vis diffuse reflectance spectra and XPS. Experiments on photodegradation of Methylene Blue (MB) under visible light irradiation were carried out to evaluate the photocatalytic abilities of N-TiO2-x%WO3. Chemical Oxygen Demand (COD) analysis was also performed to evaluate the mineralization abilities of N-TiO2-x%WO3. It is shown that the N-TiO2-x%WO3 exhibited higher COD removing rates compared with Degussa P25. The color bleaching rates of N-TiO2-x%WO3 were equal to that of Degussa P25. The enhanced photocatalytic activities were probably related to the strong absorption abilities of the N-TiO2-x%WO3.

Abstract: The objective of this study is to evaluate the performance of photocatalysis/hydrogen peroxide/metal membrane system. Metal membrane for the separation of TiO2 particles was used in an experiment and nominal pore size is 0.5 μm. Hydrogen peroxide was tested as oxidants. The removal efficiency of CODCr and color for initial hydrogen peroxide concentration increases rapidly with an increase in the hydrogen peroxide concentration up to 50 mg/L. The removal efficiency of of CODCr and color for 50 mg/L of initial hydrogen peroxide concentration was about 95 % and 98 %, respectively. However, the addition of hydrogen peroxide over 50 mg/L inhibits the system efficiency. The addition of hydrogen peroxide in UV/TiO2 system enhanced removal efficiency of CODCr and color compared to no addition of hydrogen peroxide. This may be ascribed to capture the electrons ejected from TiO2 and to produce OH radicals. The application of metal membrane in UV/ TiO2/H2O2 system enhanced removal efficiency of CODCr and color due to the adsorption of metal membrane surface as well as the production of OH radical. In application of metal membrane with nominal pore size 0.5 μm, TiO2 particles were effectively separated from the treated water by metal membrane rejection. Photocatalytic metal membrane was much smaller resistance than these of humic acid, TiO2 and humic acid/ TiO2 due to humic acid degradation of photocatalytic reaction.

Abstract: Nanoscale TiO2 is widely used in consumer products like sunscreen and cosmetics. The establishment of damage evaluation test method was attempted to examine the potential neurotoxicity of nanoscale TiO2 to human body skin in vitro model. The emergence amounts of carbon dioxide, which was expected one of the generation products from the skin according to the titania photocatalyst nanoparticles activity under UV / visible light radiation, were identified and measured by the gas analyzer. It was found that it could evaluate the degrees of damage to skin with the photocatalysts activity by using the new evaluation test method considered.

Abstract: A novel photoresponsive zirconia (ZrO2) precursor solution was prepared using zirconium tetra-n-butoxide, 4-(phenylazo)benzoic acid and ethyleneglycol monomethylether. Two kinds of ZrO2 films were prepared using the photoresponsive ZrO2 precursor solution and by dip-coating while applying an electric field to the substrates: one was the film prepared with ultraviolet (UV) irradiation to the solution and as-deposited films; the other was the film prepared without UV irradiation. It was found that the surface roughness of films was greatly changed by UV irradiation. Furthermore, the photocatalytic activity of the rough film was greater than that of the smooth film.

Abstract: To obtain porous TiO2 film, the precursor sol was prepared by hydrolysis of Ti isopropoxide and then complexed with trehalose dihydrate. The porous TiO2 film was fabricated by dip-coating technique on glass substrates using this solution. The TiO2 film was calcined at 500 °C. The maximum thickness of the film by one–run dip-coating was ca. 740 nm. The film was composed of nanosized particle and pore. The porosity of the TiO2 film was increased by the addition of trehalose dihydrate to the sol. The porous TiO2 films were calcined at various temperatures. The effects of the calcination temperature on the microstructure of the porous TiO2 film were investigated. The porous film prepared from sol containing trehalose still kept the porous structure for calcination at 950 °C. The phase transition temperature from anatase to rutile of the film was shifted from 650 to 700 °C by trehalose addition to the sol.

Abstract: Due to excellent photocatalytic and optical properties of titanium dioxide (TiO2), it has been applied in several products such as food packaging plastics, materials for vehicles or for buildings and sunscreen-protecting cosmetics. In this present work, the synthesized as well as commercial TiO2 was coated onto a household curtain fabric for anti-microbial and ultraviolet (UV) shielding functions. The coating was performed by inducing the deposition of TiO2 layer from the Ti precursor onto the fabric surface pre-treated with silane adhesive agent so as to improve the adhesion. Ag nanoparticles were also incorporated in some samples to further improve the antibacterial function. Anti-bacterial activities of the coated fabric were evaluated by standard qualitative test (the Kirby-Bauer test (AATCC 147)). Efficiency for UV shielding was evaluated by measuring a UV-Vis reflection of the coated fabrics both before and after subjecting to several washing cycles. The result showed that the TiO2-coated fabrics developed had potential as antibacterial and UV shielding for the curtain industry.

Abstract: Titanium dioxide nanofibers were fabricated by electrospinning technique. The titania solutions were obtained from adding various types of Ti precursor (Ti(OBu)4, Ti(OiPr)4, and Ti(OPr)4) to an ethanol solution containing polyvinyl pyrrolidone (PVP). Acetic acid was used to stabilize the solution and to control the hydrolysis reaction. The porous and well-defined crystalline structure was obtained after calcined at 450oC for 1 h. The thermal behavior, phase composition including crystallite size, as well as the morphology of as-synthesized nanofibers was obtained from thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. The average diameter of these nanofibers was in the range from 100 to 400 nm depending on titania precursor. The photocatalytic activity of TiO2 fibers were evaluated for NOx degradation in a gaseous phase. The results demonstrated that at the same catalyst loading, the photocatalytic activity of TiO2 nanofiber was higher than the commercial Degussa P-25.

Abstract: This study was conducted to evaluate the effect of a photocatalysis/oxidant system for the treatment of humic acid and heavy metals in aqueous solutions. Hydrogen peroxide, ozone and potassium peroxodisulfate were tested as oxidants. The effect of the oxidant concentration was conducted with a pH of 7, a UV intensity of 64 W and a TiO2 dosage of 0.3 g/L. The addition of oxidants over the amounts of H2O2 50 mg/L, O3 20 g/m3 and K2S2O8 50 mg/L inhibits the system efficiency. The negative effect of the high concentration of oxidants likely results from OH radical quenching caused by the excess oxidant. Therefore, the optimal dosages for the oxidants such as a hydrogen peroxide, ozone and potassium peroxodisulfate were found to be 50 mg/L, 20 g/m3 and 50 mg/L, respectively. The addition of an oxidant in the UV/TiO2 system enhanced the degradation efficiency of humic acid and heavy metals compared to no addition of an oxidant. The degradation efficiency of humic acid and heavy metals was much greater for the UV/TiO2/H2O2 system.