Selection of TiO2-support:: UV-transparent alternatives and long-term use limitations for H2S removal

Supported-TiO2 is commonly used for the photocatalytic treatment of gas streams. Nevertheless, selection of the best support is not a trivial task. Cheap, lightweight and easily shaped polymeric materials which are transparent in the TiO2 activation range (poly(ethylene terephthalate) and cellulose acetate) were used as supports, as an alternative to borosilicate glass or opaque monoliths. The supports were coated with TiO2 sols containing anatase particles. Different treatments were applied to the sols in order to improve particle crystallinity and wettability on plastic surfaces. The resistance of the coated and uncoated supports against weathering and the photocatalytic activity for elimination of H2S from polluted air were tested. Both supports were successfully coated with TiO2. PET supports displayed the higher photocatalytic activity, while TiO2 caused the degradation of CA supports under UV illumination. The highest activity for H2S destruction was reached with 20% RH and increasing the temperature of operation in the range of 33-50 degrees C resulted in higher conversion. Sulfate and SO2 were detected as byproducts, being the photocatalytic activity reduced when sulfate accumulates on the surface. Different washing procedures for removing the sulfate from the supported photocatalysts were tested. A simple wash with distilled water was found to successfully recover most of the initial activity of the photocatalyst, although basic pH or higher temperatures accelerate sulfate removal. (C) 2007 Elsevier B.V. All rights reserved.