Coating of expanded polystyrene spheres by TiO2 and SiO2–TiO2 thin films

Expanded polystyrene spheres (EPS) were coated by SiO 2 –TiO 2 or TiO 2 for application as a fluidized bed in the photocatalytic reactor. Silica coating was realized by the sol–gel process carried out in a vacuum evaporator at 60–70 °C. The most uniform and thin layer of silica coating was obtained by the Stöber method based on the hydrolysis of tetraethyl orthosilicate (TEOS) catalysed by an ammonia solution. Effective TiO 2 coating was obtained by the immersion of EPS in the titania aqueous suspension and evaporation of water in a vacuum evaporator. Heating of EPS spheres coated by SiO 2 , TiO 2 or SiO 2 –TiO 2 at the temperatures of 120–140 °C resulted in a shrinkage of their volume. For the thick layer coating, a strong corrugation of EPS surface was observed. The photocatalytic tests showed, that highly corrugated surface of coated EPS slowed down ethylene decomposition, whereas a thin layer coating of both, SiO 2 and TiO 2 was advantageous.