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.