Removal of emergent contaminants: Integration of ozone and photocatalysis

A mixture of nine pharmaceuticals has been treated by means of the systems: UV-B(313 nm), O3, UV-B(313 nm) + TiO2, O3 + UV-B(313 nm), and O3 + UV-B(313 nm)+TiO2. 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 TiO2 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, O3 + UV-B(313 nm) + TiO2, achieved the highest TOC abatement (95%). Use of ozone in photocatalytic processes involves an increase in hydroxyl radical generation.

► Quantum yields of pharmaceuticals at 313 nm are calculated. ► Ozone is an efficient oxidant of pharmaceutical compounds. ► Photocatalysis achieves 60% TOC reduction. ► Photolytic ozonation improves single ozonation leading to 85% mineralization. ► Photocatalytic ozonation reduces 95% initial TOC content.