Calcium-promoted Catalytic Degradation of PCDDs, PCDFs, and Coplanar PCBs under a Mild Wet Process
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- 作者：Yoshiharu Mitoma ; Norie Tasaka ; Maki Takase ; Taizo Masuda ; Hideki Tashiro ; Naoyoshi Egashira ; and Takashi Oki
- 刊名：Environmental Science & Technology
- 出版年：2006
- 出版时间：March 15, 2006
- 年：2006
- 卷：40
- 期：6
- 页码：1849 - 1854
- 全文大小：98K
- 年卷期：v.40,no.6(March 15, 2006)
- ISSN：1520-5851
文摘
The authors achieved highly efficient degradation ofpolychlorinated aromatic compounds, including polychlorinated dibenzo-p-dioxins, dibenzofurans, and dioxin-likecompounds such as coplanar polychlorinated biphenyls (co-PCBs), which are known as persistent organic pollutants.Degradation was accomplished in 24 h through a simplestirring operation using safe and high workability metalliccalcium, which acts as both a scavenger and a reducingagent, and Rh/C catalyst in an alcohol solution under mildconditions in a sealed tube at 25 
C without a temperatureincrease within 0.15 MPa of increasing internal pressureduring the reaction. In this system, reductive dechlorinationby metallic calcium and catalytic reduction by Rh/Cand generated hydrogen gas, without any external additionof hydrogen, exert a synergistic effect on the degradationof chlorinated compounds. Alcohol was used as aproton source and hydrogen, which was generated by aside reaction, causes an increase in the activity of Rh/Ccatalyst. Through the degradation of 4-chloroanisole inethyl alcohol, anisole and cyclohexyl methyl ether wereobtained in good conversions. Using ethyl alcohol as a solvent,treatment of dioxins and co-PCBs in a solution wasmarkedly effective for degradation to reduce 2806 pg TEQ/ml of initial concentration to 31.8 pg TEQ/ml; its yieldwas 98.5%. Moreover, degradation in methyl alcohol tookplace in a 99.3% yield. That concentration ultimatelyreached 20.3 pg TEQ/ml under a mild wet process. Allcongeners of dioxins and co-PCBs were degraded in highconversions. In this degradation, lower aliphatic alcohol,such as methyl alcohol, is effective for making a new calciumsurface as compared to alcohol with more methylenechains. In addition, it seemed that a higher pressure ofhydrogen was easily generated in methyl alcohol, and thencatalytic degradation was effectivley influenced.
C without a temperatureincrease within 0.15 MPa of increasing internal pressureduring the reaction. In this system, reductive dechlorinationby metallic calcium and catalytic reduction by Rh/Cand generated hydrogen gas, without any external additionof hydrogen, exert a synergistic effect on the degradationof chlorinated compounds. Alcohol was used as aproton source and hydrogen, which was generated by aside reaction, causes an increase in the activity of Rh/Ccatalyst. Through the degradation of 4-chloroanisole inethyl alcohol, anisole and cyclohexyl methyl ether wereobtained in good conversions. Using ethyl alcohol as a solvent,treatment of dioxins and co-PCBs in a solution wasmarkedly effective for degradation to reduce 2806 pg TEQ/ml of initial concentration to 31.8 pg TEQ/ml; its yieldwas 98.5%. Moreover, degradation in methyl alcohol tookplace in a 99.3% yield. That concentration ultimatelyreached 20.3 pg TEQ/ml under a mild wet process. Allcongeners of dioxins and co-PCBs were degraded in highconversions. In this degradation, lower aliphatic alcohol,such as methyl alcohol, is effective for making a new calciumsurface as compared to alcohol with more methylenechains. In addition, it seemed that a higher pressure ofhydrogen was easily generated in methyl alcohol, and thencatalytic degradation was effectivley influenced.