Preparation, stabilization and characterization of TiO2 on thin polyethylene films (LDPE). Photocatalytic applications

An innovative way to fix preformed nanocrystalline TiO2 on low-density polyethylene film (LDPE-TiO2) is presented. The LDPE-TiO2 film was able to mediate the complete photodiscoloration of Orange II using about seven times less catalyst than a TiO2 suspension and proceeded with a photonic efficiency of ∼0.02. The catalyst shows photostability over long operational periods during the photodiscoloration of the azo dye Orange II. The LDPE-TiO2 catalyst leads to full dye discoloration under simulated solar light but only to a 30% TOC reduction since long-lived intermediates generated in solution seem to preclude full mineralization of the dye. Physical insight is provided into the mechanism of stabilization of the LDPE-TiO2 composite during the photocatalytic process by X-ray photoelectron spectroscopy (XPS). The adherence of TiO2 on LDPE is investigated by electron microscopy (EM) and atomic force microscopy (AFM). The thickness of the TiO2 film is seen to vary between 1.25 and 1.69 μm for an unused LDPE-TiO2 film and between 1.31 and 1.50 μm for a sample irradiated 10 h during Orange II discoloration pointing out to a higher compactness of the TiO2 film after the photocatalysis.