ATTACHMENT OF TIO2 POWDERS TO HOLLOW GLASS MICROBEADS - ACTIVITY OF THE TIO2-COATED BEADS IN THE PHOTOASSISTED OXIDATION OF ETHANOL TO ACETALDEHYDE

Methods for attaching n-TiO2 particles to hollow microbeads of 80-100-mu-m average diam and 0.4-0.7 g cm-3 density are discussed. The floating photoactive microbeads were designed for use in solar-assisted oxidative dissolution of oil films on water. Photoactive beads caused the oxidation of ethanol molecules by dissolved dioxygen to acetaldehyde when exposed to > 3 eV incident photons. Particularly photoactive beads were obtained by attaching Degussa P25 TiO2 particles to aluminosilicate glass microbeads of approximately 10-mu-m wall thickness by physisorbing the TiO2 particles and bonding thermally at 300-degrees-C. The TiO2 thermally bonded to aluminosilicate beads was stable in water and UV light, producing 0.7 mol of acetaldehyde per einstein. Acetaldehyde was produced at an efficiency of 0.5 mol/einstein in the photoassisted oxidation of ethanol on TiO2-activated borosilicate microbeads, which were made by a process where triethoxysilane was used as binder and ethanol was eliminated in the reaction with surface OH groups. One week of exposure to water caused the borosilicate glass microbeads to dissolve. The aluminosilicate glass was, however, not water-soluble, and the bound TiO2 particles did not detach from the bead.