(708d) Investigation of Titania Nanotube Physicochemical Properties On Photocatalytic Degradation Kinetics

Heterogeneous semiconductor photocatalytic degradation of water contaminates has attracted the attention of researchers for many years. Much interest has been focused around utilizing titanium dioxide (TiO2) as the photocatalyst for its photo-stability over a wide pH range, compatibility with other photoactive materials, and environmental friendliness. Recently, titanium dioxide nanotubes (TNT) formed via anodic oxidation of titanium sheets has attracted much attention due to its simple synthesis and improved photocatalytic activity over its nanoparticle counterparts.

This work is comprised of two parts. In the first part we have investigated the effect of operating conditions and catalyst physicochemical properties on the reaction kinetics of the photocatalytic degradation of a model compound, methyl orange. The overall initial reaction rate demonstrates three types of dependence on dye concentration, with Langmuir-Hinshelwood kinetics observed at low dye concentrations. The effect of light intensity, dye concentration, external bias, and pH has all been examined for such a system.

The second part of this work consists of examining nanotubes grown on different titanium geometries. When anodizing titanium sheets, only a few microns of the titanium backbone are utilized, thus much titanium metal goes to waste. Hence, TNTs have been formed over titanium wires (0.25-0.5mm). TNT formed over titanium wires show a significant improvement in photocatalytic activity compared to the nanotubes formed over foils. This is evident when the fractional conversion of a textile dye, methyl orange, doubles for wires in the presence of nanotubes of identical dimensions illuminated over the same geometrical area. Higher degradation rates for TiO2-Pt heterocatalyst over foils are matched by the TNT formed over wires. The formation of TNT over wires can be considered as an effective alternate to improve photodegradation rates by avoiding expensive additives.