Photocatalytic hybrid devices: an innovative strategy for pollutants removal from water

Since the mid-1990s, numerous studies on the treatment of natural and industrial waters by photocatalysis have been reported. The photocatalytic process can completely degrade several organic compounds [1] and is promising in the case of polluted surface waters [2], such as lakes or seas, whose contamination may arise from industrial activities, but also from catastrophic events. In this study, a photocatalytic floating hybrid device was developed for environmental remediation applications in the case of surface waters containing organic contaminants and their vapors, such as fuels, oils and chemical products. In fact, it may be difficult to remove these compounds using conventional remediation techniques due to the hydric area dimensions to be reclaimed. The innovative device proposed here is a multilayer polymeric/TiO2 composite with a hydrophobic/superhydrophobic side, necessary to permit the device flotation during its application in water, and a photocatalytic layer active in the degradation of water pollutants. The hydrophobic side was obtained by synthesizing an oxygen permeable Polyacrylate-based polymer with high photochemical, mechanical and thermal resistance. A novel procedure involving the use of fluorinated co-monomers and controlling the polymeric foil morphology during solvent casting deposition was developed [3,4]. On the other side of the polymeric foil, the photoactive TiO2-based layer was obtained by an ad hoc multi-layer spray-coating deposition of a home-made transparent titania sol. The procedure permitted both to preserve the polymeric support properties and to favor the adhesion of the inorganic coating onto the organic surface [4], via a protective interlayer made of SiO2 microparticles, prepared by adopting the Stöber method. Starting from a multilayer hybrid composite, a highly versatile photocatalytically active device was developed: the possibility to easily modulate the dimension of such device can pave the way towards new and strategic applications for both natural and industrial water treatments.