Destruction of pentachlorobiphenyl in soil by supercritical CO(2) extraction coupled with polymer-stabilized palladium nanoparticles.
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.
Wang
Joanna Shaofen
JS
Department of Chemistry, University of Idaho, Moscow, ID 83844, USA.
Chiu
KongHwa
K
Department of Applied Science, National Dong Hwa University, Hualien 970, Taiwan, ROC. Electronic address: ckh@mail.ndhu.edu.tw.
D002245:Carbon Dioxide / Q000737:chemistry; D002384:Catalysis; D025924:Chromatography, Supercritical Fluid / Q000379:methods*; D052918:Environmental Restoration and Remediation; D053768:Metal Nanoparticles / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry*; D011078:Polychlorinated Biphenyls / Q000032:analysis* / Q000302:isolation & purification; D011108:Polymers / Q000737:chemistry; D012989:Soil Pollutants / Q000032:analysis* / Q000302:isolation & purification
D011108:Polymers; D012989:Soil Pollutants; D002245:Carbon Dioxide; D010165:Palladium; D011078:Polychlorinated Biphenyls