Suppression of dioxin emission in co-incineration of poly(vinyl chloride) with TiO2-encapsulating polystyrene

This paper presents an approach to the suppression of the emission of dioxin and its precursors as a result of the co-incineration of poly(vinyl chloride) (PVC) with TiO2-encapsulating polystyrene (TEPS), in which TiO2 nanoparticles with the capacity to adsorb dioxin and its precursors are encapsulated without significant agglomeration. Field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were used to show that spherical PS particles encapsulating a uniform dispersion of TiO2 nanoparticles are obtained through the dispersion polymerization of styrene in an aqueous ethanol medium. To facilitate the encapsulation, the surface of the TiO2 nanoparticles was modified with a polymerizable organic silane linker prior to polymerization. For comparison purposes, experiments were performed in which PVC was coincinerated with neat PS (PVC/PS), TiO2-encapsulating PS (PVC/TEPS), and mechanically mixed TiO2/PS (PVC/PSMTiO2). Qualitative and quantitative investigations of the suppression of the emission of a model dioxin and its precursors were performed by analyzing the exhaust gases from the co-incinerations using gas chromatography/ mass spectrometry (GC/MS). The results show that the addition of Ti02 nanoparticles into co-incineration systems reduces the concentration of the dioxin and its precursors in exhaust gases. Moreover, the quantitative removal efficiencies for PVC/TEPS and PVC/PS-MTiO2 indicate that the suppression is successfully enhanced by the TiO2-encapsulation: increases in the dispersity of the nanoparticles result in improved adsorption of the dioxin and its precursors.