Removal of emergent contaminants: integration of ozone and photocatalysis.

Abstract A mixture of nine pharmaceuticals has been treated by means of the systems: UV-B(313 nm), O 3 , UV-B(313 nm) + TiO 2 , O 3  + UV-B(313 nm), and O 3  + UV-B(313 nm)+TiO 2 . Simple photolytic or ozonation processes lead to a deficient total organic carbon (TOC) elimination after 120 min of exposure (25 and 30% conversions, respectively). Addition of a photocatalyst such as titanium dioxide significantly enhanced the mineralization degree, a 60% TOC conversion was obtained. A TiO 2 load optimum around 0.25 g L −1 was observed. No loss in photoactivity was experienced after 2 reuses. Due to ozone photodegradation, the combination of ozone and radiation increased the generation of hydroxyl radicals. As a consequence, TOC removal was increased to a value in the proximity of 85%. The most complex system, O 3  + UV-B(313 nm) + TiO 2 , achieved the highest TOC abatement (95%). Use of ozone in photocatalytic processes involves an increase in hydroxyl radical generation.