Photoelectrochemical advanced oxidation processes on nanostructured TiO2 catalysts: Decolorization of a textile azo-dye

Abstract

This work describes a novel approach for water treatment by photoelectrocatalysis, based on nanostructured TiO2. The decolorization of aqueous solutions containing the azo dye RR243 is carried out in a tubular photocatalytic reactor working in semi batch mode under electrical polarization of the catalyst. Two different nanostructured catalysts were tested: nanotubular TiO2 obtained by conventional anodization (CA), and a novel photoactive nanoporous TiO2 obtained by plasma electrolytic oxidation (PEO). Neither UV irradiation of the TiO2 catalysts nor the electrical bias individually considered lead to a significant reduction of the dye concentration. By irradiating the catalysts with UVC light while applying an electrical bias to the same, the concentration of the dye decreased from 25 L to 2.5 mg/L using the nanotubular CA TiO2 catalyst, and to less than 1.8 mg/L using the novel nanoporous PEO TiO2 in 50 min. The main advantages of this method over current approaches for the degradation of pollutants are both the considerable processing time reduction and a suitable and easy to scale up reactor design. A further advantage is the relatively easyness in the production of the TiO2 catalysts by PEO.