Immobilization of TiO2 nanoparticles in polymeric substrates by chemical bonding for multi-cycle photodegradation of organic pollutants

Nano titanium dioxide (TiO2) photocatalyst is generally immobilized onto the matrix through the physical absorption, hydrogen bonding or chemical bonding, which is utilized for the application of wastewater treatment. In this research, TiO2 nanoparticles were immobilized in polyvinyl alcohol (PVA) matrix via solution-casting combined with heat-treatment method. Structure characterization indicated that Ti-O-C chemical bond formed via dehydration reaction between TiO2 and PVA during the heat treatment process, and TiO2 nanoparticles had been chemically immobilized in PVA matrix. Photodegradation results of methyl orange (MO) showed that the film with 10 wt% TiO2 and treated at 140 degrees C for 2 h exhibited a remarkable ultraviolet (UV) photocatalytic activity, approximately close to the TiO2 slurry system. This was mainly attributed to the fixation effect by Ti-O-C chemical bonds, which was indirectly confirmed by the slight loss of TiO2 photocatalysts even after 25-cycle use. In addition, the good swelling ability of PVA matrix provided the MO molecules with more opportunities to fully contact with TiO2, thus benefited the photocatalysis. This route to chemically immobilize TiO2 nanoparticles is simple and cheap to prepare polymer/TiO2 hybrid materials with high photocatalytic activity for multi-cycle use, which is of significance to the practical application of TiO2 catalysts. (C) 2012 Elsevier B.V. All rights reserved.