Solar Light-Induced Decolorization of Safranin O Using Unmodified and Gold-Modified Semiconductor Oxides

Unmodified and gold-modified semiconductor oxides were used for the complete decolorization of non-buffered aqueous safranin O solutions. Photocatalytic properties of commercially available ZnO and TiO2 (anatase nanopowder) were compared with those of gold-modified ZnO (Au/ZnO). Au/ZnO was obtained from commercial ZnO powder through direct current sputter coating. ZnO-based catalysts show significantly higher decolorization power in comparison with TiO2. Au/ZnO show slightly higher activity than unmodified ZnO. Decolorization of safranin O using Au/ZnO was additionally tested in different types of mineral water. The decolorization efficiency in mineral waters was negatively correlated with the dry residue content (180 °C) and in all cases was less than in distilled water. The inhibiting effect of hydrogen carbonate was additionally investigated.