TiO2/polymer composite materials with reduced generation of toxic chemicals during and after combustion -: effect of HF-treated TiO2

The effect of HF treatment of TiO2 on its adsorption capability for toxic aromatic compounds generated during polymer combustion was studied. Compared with the non-treated TiO2, ca. 3 times higher adsorption capability for dibenzofuran was detected on the HF treated TiO2 at 200 degreesC. Incorporation of HF-treated TiO2 into poly(vinyl chloride) (PVC) resulted in reduced generation of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in the exhaust gas and increased formation of these compounds in the ash when the TiO2/PVC Composite film was incinerated at 450 degreesC. The higher adsorption capability of HF-treated TiO2 for aromatic compounds may partially explain this result. It was found that HF treatment causes increase in the amount of acid sites on the TiO2 surface, which may thus promote its adsorption capability for aromatic compounds because of the enhanced interaction between the surface acid sites and the pi electrons of the aromatic compounds. Importantly, the dioxins trapped on the TiO2 (a well-known photocatalyst) in the ash can be photocatalytically decomposed under artificial ultraviolet light or sunlight, with only harmless TiO2 powder remained eventually, so they would become no environmental problem. We found that HF-treatment gives almost no impact on the photocatalytic activity of the TiO2. (C) 2002 Elsevier Science Ltd. All rights reserved.