title: Destruction of pentachlorobiphenyl in soil by supercritical CO(2) extraction coupled with polymer-stabilized palladium nanoparticles.
abstract: 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.
authors.affiliation: Department of Chemistry, University of Idaho, Moscow, ID 83844, USA.
authors.forename: Joanna Shaofen
authors.initials: JS
authors.lastname: Wang
authors.affiliation: Department of Applied Science, National Dong Hwa University, Hualien 970, Taiwan, ROC. Electronic address: ckh@mail.ndhu.edu.tw.
authors.forename: KongHwa
authors.initials: K
authors.lastname: Chiu
mesh_terms: 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
chemical_list: D011108:Polymers; D012989:Soil Pollutants; D002245:Carbon Dioxide; D010165:Palladium; D011078:Polychlorinated Biphenyls