Preparation and characterisation of silver- or copper-doped TiO2 catalysts and their catalytic activity in dye degradation

In this study, silver- or copper-doped TiO2-Ce-, TiO2-La-, and commercial TiO2 (P25)-supported catalysts were prepared. The catalysts and supports were characterised by powder X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and nitrogen adsorption studies. UV-light-assisted heterogeneous Fenton-like oxidation of two different-structure dyes (anionic azo dye Orange II, CI Acid Orange 7 and cationic triphenylmethane dye Crystal Violet, CI Basic Violet 3) was investigated over the catalysts. Higher catalytic activity was observed in the oxidation of Orange II than in the oxidation of Crystal Violet. For both dyes, the TiO2-Ce and TiO2-La-supported catalysts, which were in the form of anatase only, gave higher photocatalytic activity than the P25-supported catalysts, which were in the form of anatase and rutile. Complete colour removal was observed during oxidation of Orange II over Cu/TiO2-Ce and Cu/TiO2-La catalysts, whereas the highest degree of decolorisation, 89.3%, was achieved by oxidation of Crystal Violet over Ag/TiO2-Ce. The pH of the solution affected the surface state of the TiO2, thus affecting the photocatalytic degradation of the dyes. The surface area of the catalysts is also a key parameter that influences their photocatalytic activity. It was observed that catalysts having higher surface areas brought about greater dye degradation.