Suppression of dioxin emission in incineration of poly(vinyl chloride) (PVC) as hybridized with titanium dioxide (TiO₂) nanoparticles

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• 作者：Sung Ho Kim ; Seong-Yong Ahn ; Seung-Yeop Kwak
• 关键词：Poly(vinyl chloride) (PVC) ; Titanium dioxide ; Nanohybrid ; Dioxins ; Incineration
• 刊名：Applied Catalysis B: Environmental
• 出版年：2008
• 出版时间：1 March 2008
• 年：2008
• 卷：79
• 期：3
• 页码：296-305
• 全文大小：1171 K

文摘

The present paper has demonstrated suppression of dioxin emission from poly(vinyl chloride) (PVC)/titanium dioxide (TiO₂) nanohybrids. In our previous paper, we suggested a novel idea for the preparation of PVC/TiO₂ nanohybrid through TiO₂ nanoparticle-integrated hyperbranched poly(-caprolactone) (HPCL-TiO₂), aiming at a breakthrough to solve the unresolved problem in the conventional PVC/TiO₂ composites related to the poor dispersion of TiO₂ nanoparticles in PVC polymer. The integration of TiO₂ nanoparticles onto the HPCL could be successfully carried out by a dip-coating method based on the spontaneous self-assembly between TiO₂ and HPCL. In this study, three kinds of hyperbranched poly(-caprolactone)s (H_nPCLs) were prepared by varying the number, n, of monomeric units on the branched backbone chains. Thereby, it was possible to control the numbers of functional ends and the contents of TiO₂ in the H_nPCL-TiO₂. The loadings of TiO₂ in the H_nPCL-TiO₂s were found to be 4.37, 3.26, and 2.93 wt % for n of 5, 10, and 20, respectively. The preparation of PVC/H_nPCL-TiO₂ (60/40) blends was performed through solution blending of H_nPCL-TiO₂ with PVC in tetrahydrofurane (THF) as solvent, and the dispersities of TiO₂ in the resulting nanohybrids were investigated by field-emission scanning electron microscope (FE-SEM) equipped with energy dispersive spectroscopy (EDS). The FE-SEM/EDS results showed that TiO₂ nanoparticles were dispersed well in PVC matrix, while some agglomerates of TiO₂ was observed in the PVC + TiO₂ sample prepared from the solution blending of PVC with the same amount of TiO₂. The incineration experiments were performed by using a temperature-controllable electric furnace at 350 °C under the flow of ambient air, and the exhaust gases resulting from the incineration process were collected. Prior to the identification of the components emitted in the incineration process, the GC experiments for calibration were performed on several commercial standards of dioxin and organic compounds known to be dioxin precursors. The GC results on the exhaust gases from the incineration of samples showed that the emissions of dioxin and precursors were largely suppressed with the increasing content of TiO₂ in PVC/H_nPCL-TiO₂, i.e., the order of PVC/H₅PCL-TiO₂ > PVC/H₁₀PCL-TiO₂ > PVC/H₂₀PCL-TiO₂, as compared with those in the neat PVC/H_nPCL without TiO₂. Especially, the PVC/H₅PCL-TiO₂ with a maximum TiO₂ loading of 1.6 wt % showed removal efficiencies of ca. 60 % up to 70 % over the dioxin and dioxin precursors, which is equivalent to one and half to several times as much as the PVC + TiO₂ samples prepared through the conventional route. The remarkable enhancement of the suppression of dioxin emission in the PVC/H_nPCL-TiO₂ might be attributed to the improvement of the degree of TiO₂ dispersion in the nanohybrid.