Photocatalytic decomposition of formaldehyde using titania coated lime tile

A traditional and popular Japanese house decorating lime tile, commercially available "Limix", was used to photodecompose the formaldehyde after coating the tile with a titania sol, which solves the problem of sick-building syndrome. A total of five kinds of lime tile samples with titania sol coating and without coating were examined by using a flow-type photoreactor based on the JIS standard to test their photocatalytic activities. The photocatalytic mechanism in the coated lime tile was also analyzed by Electron Paramagnetic Resonance Spectroscopy (EPR). The results show that a high removal efficiency of formaldehyde was achieved when using the lime tile combined with commercially available zeolite compared to the lime tile immobilized titania photocatalyst. The EPR spectrum indicates that oxygen centered radicals and surface trapped holes are present in the titania sol, but it is much different from the spectrum observed in the pure anatase and Degussa P25 titania. It means that there are different characteristics among these systems on the photocatalysis mechanism.