Efficient degradation of dye pollutants on nanoporous polyoxotungstate-anatase composite under visible-light irradiation

A novel photocatalyst, nanoporous anatase TiO2 crystalline particles coupled by homogeneously dispersed Keggin unit, H3PW12O40/TiO2, was prepared by a simple and rapid process, i.e., at a lower temperature (200degreesC) by combined sol-gel and programmed temperature hydrothermal methods. The resulting material was characterized by UV diffuse reflectant spectroscopy, XRD, P-31 MAS NMR, TEM, and nitrogen adsorption. This new photocatalyst exhibited visible-light photocatalytic activity to decompose 10 various organic dyes in aqueous systems. It was attempted to determine the feasibility of such a degradation by varying the chemical structures, either azoic (Congo Red (CR), Methyl Orange (MO), Ponceau G (PG), Orange II (OII), and Eriochrome Blue Black B (EB)), or anthraquinonic (Alizarin S (AS)), or heteropolyaromatic (Methylene Blue (MB)), or fluorescent (Neutral Red (NR), Rhodamine B (RB)), or sulfonic (Fuchsin Acid (FA)). The intermediates and the final products of degradation were detected by electrospray mass spectrometer (ES-MS) and ion chromatography (IC). According to the experimental results, we proposed a possible mechanism of the photodegradation of dyes under visible-light irradiation in the aqueous system. (C) 2004 Elsevier B.V. All rights reserved.