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Adsorption And Simultaneous Dechlorination Of PCBs On GAC/Fe/Pd: Mechanistic Aspects And Reactive Capping Barrier Concept
Citation:
Choi, H., S. Agarwal, AND S. R. AL-ABED. Adsorption And Simultaneous Dechlorination Of PCBs On GAC/Fe/Pd: Mechanistic Aspects And Reactive Capping Barrier Concept. J. Schnoor (ed.), ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 43(2):488-493, (2009).
Impact/Purpose:
The objective is to (1) investigate mechanistic aspects of the adsorption and dechlorination of a PCB congener and partitioning of a reaction product biphenyl (Bp) in contrast with neat GAC through sacrificial batch experiments with aqueous 2-chlorobiphenyl (2-CIBP) as a model PCB in the absence of other organic materials and ionic species; (2) demonstrate the concept of a "reactive" capping barrier composed of the RAC for the remediation of PCBs-contaminated groundwater and sediment; and (3) briefly discuss its general concerns to be addressed in the future.
Description:
There are many concerns and challenges in current remediation strategies for sediments contaminated with polychlorinated biphenyls (PCBs). Our efforts have been geared toward the development of granular activated carbon (GAC) impregnated with reactive iron/palladium (Fe/Pd) bimetallic nanoparticles (reactive activated carbon (RAC)). In this study, we elucidate the mechanistic aspects of the hybrid RAC system dechlorinating 2-chlorobiphenyl (2-CIBP) in the aqueous phase. The following reactions occurred in parallel or consecutively: (i) 2-CIBP is promptly and completely sequestrated to RAC phase, (ii) the adsorbed 2-CIBP is almost simultaneously dechlorinated by Fe/Pd particles to form a reaction product biphenyl (BP), and (iii) the BP formed is instantly and strongly adsorbed to RAC. The 2-CIBP adsorption and dechlorination rate constants were estimated through simple first-order reaction kinetic models with an assumption for unextractable portion of carbon in RAC. The extent of 2-CIBP accumulation and BP formation in RAC phase could be well explained by the kinetic model and adsorption was found to be the rate limiting step for overall reaction. On the basis of our observations, a new strategy and concept of "reactive" cap/barrier composed of RAC was proposed as a new environmental risk management option for PCBs-contaminated sites.
URLs/Downloads:
Adsorption and Simultaneous Dechlorination of PCBs, etc.
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