以超臨界二氧化碳移除及降解持久性有機污染物

Removal and Degradation of Persistent Organic Pollutants by Supercritical Carbon Dioxide

陳香羽(Hsiang-Yu Chen)

指導教授 ： 葉華光

中原大學/理學院/化學研究所/博士(2012年)

https://doi.org/10.6840/cycu201200893

摘要

持久性有機污染物(Persistent Organic Pollutants, POPs)具有四種特性：持久性、半揮發性、生物累積性及高毒性。不管是對於環境或是人體健康都有很大的影響，移除這些污染物或是降解使其毒性降低顯得非常重要。

第一部分是藉由礦物酸抑制和超臨界二氧化碳萃取以移除固態基質中之全氟化合物。選用硝酸當作抑制劑，接著在含有甲醇共溶劑的超臨界二氧化碳中萃取以移除固態基質中之全氟辛酸和全氟辛烷磺酸。最佳實驗條件為加入16M硝酸再添加20% (v/v)甲醇，於壓力200 atm與溫度50℃ 條件下，萃取時間70分鐘(先以40分鐘進行靜態萃取，再動態萃取30分鐘)。接著利用高效液相層析質譜儀進行定性和定量，全氟辛酸和全氟辛烷磺酸在濾紙或是實驗衣布料之萃取率(二次萃取)約100%和80%。此方法提供一個準確、有效及綠色化學的方法。

第二部份將鈀金屬奈米顆粒支撐在高密度聚乙烯上接著應用於超臨界二氧化碳中對戴奧辛類化合物(含多氯戴奧辛、多氯呋喃)及多溴聯苯進行降解反應。催化劑的製備經過三個步驟：(1)超臨界流體發泡，(2)超臨界流體浸漬，(3)將被包覆在高密度聚乙烯的鈀金屬前驅物還原成金屬的還原步驟。將製成的微孔洞鈀-高密度聚乙烯催化劑利用戴奧辛類化合物的去氯氫化反應及多溴聯苯的去溴氫化反應評估催化劑的活性。在200大氣壓二氧化碳包含10大氣壓的氫氣和反應溫度50-100℃的環境下，可以有效的把多氯戴奧辛、多氯呋喃(1,6-Dichlorodibenzo-p-dioxin, 1,6-DCDD和2,8-Dichlorodibenzofuran, 2,8-DCDF)及多溴聯苯(4-bromobiphenyl, 4-PBB)分別降解成較不具毒性的化合物dodecahydro-DD、dodecahydro-DF和聯二環已烷(bicyclohexyl)。此催化劑製備的方法簡單並且戴奧辛類化合物在經過50次以上的去氯氫化反應，多溴聯苯進行去溴氫化反應達40次以上均仍不失其催化活性，且不需要經過複雜的回收和清潔過程則可與產物分離並且重複使用。本降解反應系統是一個對環境較友善的方法，在未來對於其他持久性污染物之降解也可以加以應用。

關鍵字

超臨界二氧化碳 ； 持久性有機污染物

並列摘要

Persistent organic pollutants (POPs) are organic pollutants that are resistant to degradation which possess four characteristics：persistence, semi-volatility, bio-accumulativeness, and high toxicity. Since POPs have great impacts on the environment and human health, the removal of these contaminants and/or their degradation present an important task for the researchers.

In the first part of this study, a simple method that employs concentrated HNO3 as a suppression agent and methanol-modified supercritical carbon dioxide (Sc-CO2) extraction is proposed for the removal of PFOS and PFOA from solid matrices. The optimal conditions were found to be 16 M HNO3 and Sc-CO2 containing 20% (v/v) methanol under 200 atm pressure at 50 °C, with 70 min extraction time (40 min for static and 30 min for dynamic extraction). PFOA and PFOS were identified and quantified by high performance liquid chromatography/mass spectrometry (HPLC/MS). The extraction efficiencies (with double extractions) are near 100% for PFOA and 80% for PFOS for both paper and fabric matrices. The results show that this method is quick, convenient, accurate, and effective, providing a promising and convenient approach to remediate the environment from the contamination of hazardous PFOA and PFOS.

In the second part, a method for the degradation of dioxins and polybrominated biphenyls (PBBs) catalyzed by palladium nanoparticles stabilized in microcellular high-density polyethylene (Pd/m-HDPE) in supercritical carbon dioxide is described. Preparation of Pd/m-HDPE is divided into three steps; foaming in supercritical fluid, impregnation in supercritical fluid, and reduction by hydrogen. Dioxins and PBBs can be effectively degraded under 200 atm of CO2 containing 10 atm of H2 at 50-100℃ using the Pd/m-HDPE catalyst. Stepwise removal of chlorine/bromine atoms takes place first, followed by hydrogenation of the two benzene rings with slower reaction rates. The Pd/m-HDPE catalyst is easy to prepare and can be reused without losing its activity even after 50 times. This heterogeneous catalyst is eco-friendly and can be easily separated from the products without complicated recovery and cleaning procedures.

並列關鍵字

Supercritical carbon dioxide ； Persistent organic pollutants

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