Determination of the photocatalytic activity of TiO2 with high adsorption capacity

Photocatalysis is often used for the decomposition of organic compounds in water, e.g., for dye decomposition. There are many problems with calculating the photocatalytic activity of photocatalysts during dye decomposition, especially in the case of photocatalysts with a high adsorption capacity because it is difficult to say whether a dye is photocatalytically decomposed or whether it is only adsorbed on photocatalyst surface. In both cases, the dye disappears from the water, but the optimal situation is when the dye is both adsorbed and decomposed on photocatalyst surface. Moreover, it is problematic to compare the photocatalytic activity of different photocatalysts when they have strong adsorption capacity. In this study a new method of measuring photocatalytic activity of photocatalysts with high adsorption capacity is presented. Reactive Red (monoazo) and Direct Green (poliazo) dyes were used to determine adsorption capacity and photocatalytic activity of commercial TiO2 Degussa P25, anatase TiO2 and carbon modified anatase TiO2.