Solid-phase photocatalytic degradation of PVC by tungstophosphoric acid - a novel method for PVC plastic degradation

The solid-phase photocatalytic degradation of polyvinyl chloride (PVC) films by tungstophosphoric acid (HPW) was investigated based on the unique redox property of heteropolyacid. PVC films doped with HPW (1.5, 2.0 wt.%) were prepared and their photocatalytic degradation was carried out under the irradiation of UV with wavelength 254 nm and visible light above 300 nm. The photocatalytic activity was determined by weight loss monitoring and scanning electron microscopic (SEM) analysis. HPW-doped PVC showed highly enhanced photodegradation. Irradiating the composite film for 250 It by visible light reduced its weight up to 70%. The photocatalytic degradation of PVC films embedded with semiconductor nanomaterials TiO2 and US was also investigated and compared with that of HPW-PVC. It was noticed that TiO2-PVC and CdS-PVC induced less degradation. The SEM images of PVC composite films further confirmed the above results. The photodegradation of PVC by boric acid and such acid catalysts implied that the high photocatalytic activity of HPW-doped PVC film was due to the unique redox property of HPW, rather than the acidity. FT-IR and UV-vis spectroscopic studies provided some preliminary results about the structure of the HPW-PVC composite system and will lay some foundations for further studying the photocatalytic mechanism. The advantages for PVC photodegradation by heteropoly compound were assessed. They show that this method possesses feasibility and, from the point of view of plastics assorting with environmental protection, provides a new way to develop photodegradable plastics. (C) 2004 Elsevier B.V. All rights reserved.