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Abstract: This work investigates the feasibility of applying photocatalytic technology for removal of volatile organic compounds (VOCs) over TiO2. A photocatalytic packed bed reactor (PPBR) was employed to determine the oxidation rates of VOCs (bezene, toluene, o-, m-, p- xylenes). TiO2 Degussa P25 was used to prepare a nanocrystalline titania paste, where glass spherules were embedded. The photocatalyst was extensively characterized by means of spectroscopy (Raman, XRD) and microscopy (SEM, AFM). Experiments were conducted under ‘real world setting’ condition of temperature (25°C ±2) and humidity (60%) while the irradiation was provided by 15W near UV lamps. The dependence of the reaction rate on light intensity as well as the deactivation of the catalyst were determined. The results indicate that the rate of the photo-oxidation process increased while increasing the intensity of UV irradiation. Using two (2) UV-A lamps, the destruction rate of benzene and toluene was 0.0429 and 0.1960μgm−2 h−1 respectively, while with four (4) UV-A lamps values of 0.6775 and 1.5301μgm−2 h−1 correspondingly were obtained. The stabilized photocatalysts present remarkable stability (no deactivation and excellent repeatability). Reproducibility tests proved that the photocatalytic activity of the photocatalyst remains intact even after thirty consecutive experiments of new added VOCs quantities. [Copyright &y& Elsevier]

Materials that contain a photocatalyst have a semi-permanent capacity for removing harmful gases from the ambient air. It is the purpose of this study to investigate the photocatalytic activity of commercial paints containing TiO2 nanoparticles towards NO and NO2. Experiments were carried out in a stainless steel (30 m-3) walk-in type environmental chamber (Indoortron), under “real world setting” conditions of temperature, relative humidity, irradiation and pollutant concentrations. Two types of nanoparticle TiO2-containing paints were tested for their depolluting properties: a mineral silicate paint and a water-based styrene acrylic paint. The results showed a significant effect of TiO2-materials in reducing NOx. It was found that up to 74% of NO and 27% of NO2 were photo-catalytically degraded by the mineral silicate paint, while degradation percentage using the styrene acrylic paint reached 91% and 71% for NO and NO2, respectively. The photo-catalytic rate of NO on the mineral and styrene acrylic paint was calculated to 0.11 μg m-2 s and 0.18 μg m-2 s, respectively, indicating higher photocatalytic performance of the organic based material. The effect of relative humidity (RH) was also investigated. An increase of RH from 20% to 50% inhibited the NOx photocatalysis on the surface of the samples. [ABSTRACT FROM AUTHOR]

Abstract: Self-assembled titanium oxide nanotubular (NTs) arrays with vertical arrangement, tailored morphological properties and variable thickness were prepared by electrochemical anodization in ethylene glycol containing electrolytes. The NTs present significant UV photocatalysis against toluene and benzene at ppb concentrations, under normal conditions of temperature and pressure. The photocatalytic activity depends on the length of the NT arrays, showing a tendency of saturation for thickness above 2.5μm and maximum efficiency for samples with thickness of 12μm. The optimum NT structures outperform over standard Degussa P25 films rendering them very promising for outdoor photocatalytic applications. [Copyright &y& Elsevier]

Abstract: Self ordered nanotubular TiO2 films of variable morphological characteristics were grown by electrochemical anodization in ethylene glycol based electrolytes. The films were incorporated in a continuous flow reactor and were evaluated for the UV photocatalytic oxidation of nitrogen oxide (NO) gas by varying the flow rate and the pollutant concentration in the 200–1000ppbv range. After a strong initial response, the photooxidation rate decreased and reached an equilibrium state. Strong dependence of the overall NO concentration on the morphological film parameters was observed which is related to the interplay of porosity and extended surface area. Saturation of the photocatalytic performance was evidenced for nanotubular films with thickness above 14μm, pointing out the limitations imposed by the UV light penetration depth and the diffusion of the gas pollutants and intermediates into the nanotube channels. Nitrates–nitrites were identified as the principle NO x photooxidation products. [Copyright &y& Elsevier]