Photoelectrocatalytic Oxidation of Methyl Orange on a TiO sub(2) Nanotubular Anode Using a Flow Cell

Methyl orange from water was removed by photocatalytic anodic oxidation using a titanium dioxide array surface. The coating was prepared by anodizing a titanium plate in an ethylene glycol electrolyte-containing NH sub(4)F followed by heat treatment to realize a photocatalytic surface under UV light. Scanning electron microscopy imaging showed that the array coating consisted of closely spaced nanotubes perpendicular to the titanium plate. The aqueous solution of methyl orange was circulated through a rectangular channel flow cell containing the coated anode. The effects of electrolyte flow rate and applied potential on the oxidation rate and efficiency were evaluated. At higher mean linear flow rates, the efficiency of the oxidation process improved, indicating a mass transport-controlled process. At more positive applied potentials, the TiO sub(2) structure deteriorated resulting in a lower oxidation efficiency. Methyl orange as a model organic dye is removed from wastewaters by photoelectrocatalytic oxidation on a TiO sub(2) nanotubular array-coated anode in a flowing electrolyte cell. The photocatalytic titanium nanotubes produce hydroxyl radicals able to oxidize the organic molecules. Effects of flow rate and applied potential on the removal efficiency are investigated.