Photocatalytic degradation of ethidium bromide over titania in aqueous solutions

The photocatalytic degradation of ethidium bromide (EtBr), a DNA intercalating pollutant, by TiO₂-based catalysts has been analyzed. Three different titanium dioxide samples synthesized by sol–gel within reverse microemulsions at different pH and thermal treatments were characterized and studied for the photocatalytic degradation of EtBr by oxygen in aqueous solutions. A commercial titania, Degussa P25, was also examined as a reference material for comparative purposes. Appreciable differences in the final structural and surface properties of these titania samples are observed which include disparities in the anatase/rutile proportions, optical absorption characteristics, EtBr chemisorption and acid–base properties. EtBr photodegradation results suggest that catalytic acid–base properties are the most relevant to explain EtBr chemisorption and play an important role in their final photocatalytic behaviour. It is stressed that photocatalysis can be an interesting alternative to other chemical or biological methods for mineralization of EtBr diluted in aqueous solutions.