Photocatalytic Oxidation-Based Water Treatment Using Nano-Structured Tio­2 Electrode: Co-Catalyst Vs. Non-Ferric Fenton

Advanced oxidation processes (AOPs) are significant in that they can overcome kinetic limitations of conventional oxidation processes in the treatment of organic contaminants. Doped TiO₂ (titania), and un-doped titania in conjunction with an electron-donor such as H₂O₂,can be used as electrodes in photocatalytic AOPs. In this study, the dye methyl orange (MO) was used as an example of the target organic contaminant. Photocatalytic degradation of the dye was studied initially using as-produced and palladium-doped titania photo-electrodes prepared using the anodic oxidation method, with nanotube (NT) and nanorod (NR) structures. Palladium was doped on the electrodes using a PdCl₂ precursor with illumination under mercury lamp. SEM and XRD were used for surface analysis and UV-Vis for monitoring photocatalytic degradation. Kinetic parameters were obtained using the Langmuir-Henshelwood model. It was determined that the rate of MO degradation was highest for the Pd-TNT electrode and 5 times slower for the Pd-TNR and the as-produced un-doped TNT electrode. The as-produced un-doped TNT electrode was then employed (coupled with an inert electrode, without any external bias) along with varying concentrations of H₂O₂,for MO degradation. Complete degradation of the dye was observed at a much faster rate than that for heterogeneous photocatalytic oxidation of the same contaminant using the Pd-TNT electrode.