Novel Mild Hydrodechlorination of PCDDs, PCDFs, and co-PCBs inside Fly Ash Using a Calcium-Promoted Rhodium Carbon Catalyst in Methanol
Yoshiharu Mitoma A C , Maki Takase A , Yoshiko Yoshino A , Taizo Masuda A , Hideki Tashiro A , Naoyoshi Egashira A and Takashi Oki BA Department of Environmental Sciences, Faculty of Life and Environmental Sciences, Prefectural University of Hiroshima, Shobara City, Hiroshima, 727-0023, Japan.
B Hiroshima City Industrial Technology Center, Naka-ku, Hiroshima, 730-0052, Japan.
C Corresponding author. Email: mitomay@pu-hiroshima.ac.jp
Environmental Chemistry 3(3) 215-218 https://doi.org/10.1071/EN06002
Submitted: 11 January 2006 Accepted: 27 April 2006 Published: 10 July 2006
Environmental Context. The generic term ‘dioxins’, the family of which includes polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and dioxin-like compounds such as coplanar polychlorinated biphenyls (co-PCBs), is used to describe highly toxic and mutagenic compounds. Many methods that involve high-temperature or high-pressure dry hydrogen conditions to ensure adequate decomposition for persistent chlorinated aromatic pollutants present disadvantages for repeated synthesis or recovery of vaporized dioxins and co-PCBs. We discovered that highly efficient degradation of dioxins in fly ash is accomplished in 24 h using metallic calcium and Rh/C in alcohol in a sealed tube at 25°C at 0.15 MPa.
Abstract. Effective hydrodechlorination of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and dioxin-like compounds such as coplanar polychlorinated biphenyls in fly ash was achieved in 24 h using a simple stirring operation in a sealed tube with metallic calcium and Rh/C catalyst in an alcohol solution at room temperature with 0.15 MPa of increasing internal pressure. The initial 7806 pg dioxin toxic equivalent (TEQ) (g of ash)–1 of dioxins in fly ash, which had adsorbed inside the solid phase, was finally degraded to 23.6 pg of TEQ (g of ash)–1, according to estimation using gas chromatography–mass spectrometry analysis.
Keywords. : catalysts — dioxins — fly ash — metallic calcium — reduction
Acknowledgements
The authors gratefully acknowledge financial support of this study from the Industrial Technology Research Grant Program (04A47002) from the New Energy and Industrial Technology Development Organization (NEDO) of Japan, and by a Grant-in-Aid for Young Scientists (B) from JSPS KAKENHI (16710053). We especially thank Mr Yamaoka and Miss Yamanaka of Ryomei Engineering Co., for their help with the analyses of dioxins and co-PCBs.
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