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), O-3, UV-B(313 nm) + TiO2, O-3 + UV-B(313 nm), and O-3 + 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 photo-degradation, 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 + UV-B(313 nm) + TiO2, achieved the highest TOC abatement (95%). Use of ozone in photocatalytic processes involves an increase in hydroxyl radical generation. (C) 2012 Elsevier Ltd. All rights reserved.