Coating of photocatalytic TiO2 and TiO2-K2O[formula omitted]nSiO2 nanocomposite thin films on limestone: Accelerated rainfall erosion tests

Abstract

UV photodegradation efficiency η of thin films, coated on limestone substrates and made with aqueous TiO2 nanoparticle dispersions, diluted waterborne potassium silicate, and TiO2-K2O×nSiO2 nanocomposite sols with various TiO2 to SiO2 molar ratio α, was measured in laboratory accelerated rainfall erosion tests on discoloring Methylene Blue dyes. Our results show that for nanocomposite with α = 2, η assumed a value between those of pure substances but its erodibility was very similar to that of titania and that for α = 1 and α = 0.2 the films behaved essentially as a pure silicate. These results shed some light on the interplay between the TiO2 to SiO2 molar ratio, the photodegradation performance, and the rain erosion resistance.