In this project photocatalytic degradation of a number of synthetic dyes is also evaluated.
Since dye molecules are designed to resist bleaching by sunlight and thus degradation under UV light takes place at a low rate. However, in photocatalysis a catalyst is used to accelerate the photoreaction. Titaniumdioxide (TiO2) commonly used catalyst has several interesting features, like high stability, low cost, non-toxic and possibilities to be used at ambient conditions.

The basic principle behind photocatalysis is relatively simple. Light energy from UV radiation excites electrons on the surface of the titaniumoxide, whereby electrons move from the valence band into the conduction band. This leaves positive “holes” in the valence band, which reacts with water leading to the production of radicals that can degrade dyes.

Though using artificial UV light for photocatalysis will increase the overall process cost. However, use of sun light can make it cost efficient and this offers an attractive treatment option as most of textile industries are situated in regions where sun energy is abundant.