Photocatalytic decomposition of benzo-[a]-pyrene on the surface of acrylic, latex and mineral paints. Influence of paint composition

Some mineral, acrylic and latex photocatalytic paints of white colour (PIGMENT) were tested for their photocatalytic properties. Benzo-[a]-pyrene (BaP) as a typical pollutant existing in air at high industrial and urban areas was selected for the photocatalytic tests. Porcelain trays were coated with the photocatalytic paints and then BaP was loaded after its dissolution in acetone. The concentration of BaP was measured by UV–vis spectroscopy. Paint composition was analysed by XRD and SEM/EDX – scanning electron microscope/energy dispersive with X-ray analysis. Samples were irradiated by the light emitted by the xenon lamp equipped with the optical filters sorting UV–vis or solar lights. It appeared that the photodecomposition of BaP was depended on the access of pollutant to the active forms of TiO2. The organic paints exhibited much higher photocatalytic activity than the mineral ones. Potassium silicate contained in the mineral photocatalytic paints reacted with the sulfite present in the Ti(OH)2, which was applied as a photoactive form of TiO2 what resulted in reducing its photocatalytic activity. The total amount of BaP decomposition was over 70% after 60 min UV–vis exposition on the acrylic and latex paints whereas only 20% on the mineral silicate ones. By applying UV–vis irradiation photodecomposition of BaP was going faster than under solar light however the similar total effect of BaP decomposition was obtained. It means that BaP can be decomposed on the surface of the photocatalytic paints exposed to the solar light, but its efficiency is dependent on the access to the photoactive form of TiO2.