Rapid removal of acetaldehyde and ethylene in the fluidized bed photoreactor filled with thermally-shrunk polystyrene spheres coated with TiO2

• Coating of EPS spheres by TiO 2 through heating at 140 °C caused their shrinkage. • Shrunk EPS-TiO 2 spheres contained EPS degradation products on TiO 2 surface. • Contaminated EPS-TiO 2 surface was purified after exposition to UV irradiation. • Cleaned EPS-TiO 2 bed was very active for photocatalytic decomposition of VOCs. • Thermal coating of EPS by TiO 2 gave very active and stable photocatalytic bed. Polystyrene spheres with a size of 1 mm were coated by TiO 2 (titanium dioxide) powder by two methods: wet impregnation from the titania slurry solution, followed by sintering at 140 °C, and dry sintering of mixed expanded polystyrene spheres with TiO 2 powder at 140 °C. Such obtained materials were applied as the fluidized beds in the continuous flow photocatalytic reactor for removal of VOCs (Volatile Organic Compounds), such as acetaldehyde and ethylene from air. Materials were characterized by SEM/EDS, optical microscope, TG and UV–Vis/DR techniques. Concentration of the outlet gas was monitored by using Gas Chromatography and mineralization degree by the CO 2 sensor. High initial concentrations of VOCs were used (439.7 mg/m 3 ) for acetaldehyde and (246.4 mg/m 3 ) for ethylene. The effect of 15 and 30 % bed fill and various gas flow rates were investigated. The photocatalytic reactor of cylindrical shape was irradiated by UV-LEDs mounted on 3 panels (16 LEDs on each panel, λ = 365 nm). The photocatalytic reactor was surrounded by these panels. Measured intensity of light transmission through the reactor varied from 0.2 to 7.5 W/m 2 , depending on the fluidized bed expansion. The total photocatalytic decompositions of both, acetaldehyde and ethylene were reached in a few minutes with high mineralization degree. Acetaldehyde decomposition was more efficient than ethylene (690 µg/min versus 80 µg/min, respectively), due to its good adsorption abilities to the titania surface. Moreover, the activity of utilized bed was stable during prolonged operation time. Thermal imaging camera measurements indicated that the temperature inside the reactor increased when UV-LEDs were lit due to the absorption of UV light by the TiO 2 coated EPS, whereas uncoated EPS didn’t transfer heat.