VOC Degradation in the Atmosphere by Nanophotocatalysts

Abstract

The paper deals with a novel method for the destruction of VOCs in air. The method is based on usage of an aqueous colloidal solution of nanocarbon-metal oxides compositions in which titanium is chosen as the metal. The colloidal solution is sprayed in the air and under natural solar radiation the nanocomposition, as a photocatalyst, forms OH-radicals in the presence of water molecules from aqueous solution drops or natural moisture. Results of laboratory tests of the method conducted with benzene, toluene, trichloroethene (TCE), cis-dichloroethene and trans-dichloroethene (DCE) in a plexiglass box with dimensions of 2,000 × 1,000 × 1,000 mm are described. The concentrations of substances in the air in the experiments were within the range 1-15 mg/m3, and the concentration of sprayed solution of nanophotocatalysts was about 0.1 g/m3. The concentration of nanophotocatalysts in the colloidal solution was 100 mg/l, and the average size of the nanocompositions and aqueous solution drops were about 5 nm and 5 μm, respectively. The temperature of the air was 25°C and the air humidity was 7-15 g/m3. The air in the box was irradiated with a 60 W UV lamp during 15 min, giving degradation efficiencies of 90-99% for all compositions. Two to three hours were necessary to reach this degradation efficiency with irradiation of the box by sunlight. Concentrations of secondary products from the VOC degradation process were below detectable levels. © Springer Science+Business Media Dordrecht 2013.