Preparation of nanocrystalline TiO2 powders for photocatalytic oxidation of phenol

Nanocrystalline TiO2 powders in the anatase, rutile, and mixed phases prepared by hydrolysis of TiCl4 solution were of ultrafine size (<7.2 nm) with high specific surface areas in the range 167 to 388 m(2)/g. In the photocatalytic degradation of phenol as model reaction, the photocatalytic properties of TiO2 nanoparticles were evaluated by use of UV-vis absorption spectroscopy and total organic carbon (TOC) content. The synthetic mixed-phase TiO2 powder calcined at 400 degrees C had higher activity than pure anatase or rutile; it degraded more than 90% phenol to CO2 (evaluated by TOC) after irradiation with near UV light for 90 min at a catalyst loading of 0.4 g/L. The TOC results indicated that rutile TiO2 crystallites of particle size 7.2 nm resulted in much better photocatalytic performance than particles of larger size. This result suggested that some intermediates, not determined by UV-vis absorption spectroscopy, existed in the solution after the photocatalytic process over the rutile TiO2 photocatalysts of larger crystallite size.