Wang Joanna Shaofen, Chiu KongHwa
Department of Chemistry, University of Idaho, Moscow, ID 83844, USA.
Department of Applied Science, National Dong Hwa University, Hualien 970, Taiwan, ROC.
Chemosphere. 2009 May;75(5):629-633. doi: 10.1016/j.chemosphere.2009.01.018. Epub 2009 Feb 10.
PCBs exhibit a wide range of toxic effects, and they are very stable compounds and do not degrade readily. Although they had been banned in the 1970s; however; it is still urgent to investigate and develop a financially viable, environmentally benign and safe technology to treat the soils contaminated by PCBs. This study investigated the feasibility of coupling of supercritical fluid carbon dioxide (ScCO(2)) extraction with polymer-stabilized palladium nanoparticles for the destruction of pentachlorinated biphenyl (2,2',4,5,5'-PCB) from contaminated sand or soil samples. The extracted 2,2',4,5,5'-PCB can be converted into non-chlorinated products by hydrodechlorination catalyzed by palladium (Pd) nanoparticles, which were stabilized in high-density polyethylene (HDPE) beads. Nearly all 2,2',4,5,5'-PCB was removed quantitatively from solid matrices at 200atm and different temperatures. The final product was proved to be biphenyl and cyclohexylbenzene. The polymer-stabilized palladium nanoparticle catalyst, which does not contact the contaminated matrix directly, can be reused without losing the high catalytic activity inherent by nanometer-sized particles. Deactivation factors such as leaching of metal particles from support, agglomeration and sintering are minimized in this catalyst system due to the unique plastic matrix environment. A combination of supercritical fluid extraction and an on-line catalytic reaction system utilizing the plastic catalysts may have great advantages over other processes for destroying toxic chlorinated compounds in environmental samples.
多氯联苯具有广泛的毒性作用，并且它们是非常稳定的化合物，不易降解。尽管它们在20世纪70年代已被禁止；然而，研究和开发一种经济可行、环境友好且安全的技术来处理受多氯联苯污染的土壤仍然十分紧迫。本研究考察了超临界流体二氧化碳（ScCO₂）萃取与聚合物稳定的钯纳米颗粒联用，用于从受污染的沙子或土壤样品中破坏五氯联苯（2,2',4,5,5'-PCB）的可行性。萃取得到的2,2',4,5,5'-PCB可通过钯（Pd）纳米颗粒催化的加氢脱氯反应转化为无氯产物，这些钯纳米颗粒稳定在高密度聚乙烯（HDPE）珠粒中。在200个大气压和不同温度下，几乎所有的2,2',4,5,5'-PCB都能从固体基质中定量去除。最终产物被证明是联苯和环己基苯。聚合物稳定的钯纳米颗粒催化剂不直接接触受污染的基质，可重复使用而不会丧失纳米级颗粒固有的高催化活性。由于独特的塑料基质环境，在该催化剂体系中，诸如金属颗粒从载体上浸出、团聚和烧结等失活因素被降至最低。超临界流体萃取与利用塑料催化剂的在线催化反应系统相结合，可能比其他用于破坏环境样品中有毒氯代化合物的工艺具有更大优势。
