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PALLADIUM/MAGNESIUM CORROSION NANO-CELLS FOR PCB DECHLORINATION
Citation:
AGARWAL, S., S. R. AL-ABED, AND D. D. DIONYSIOU. PALLADIUM/MAGNESIUM CORROSION NANO-CELLS FOR PCB DECHLORINATION. Presented at 39th Central Regional Meeting, Covington, KY, May 20 - 23, 2007.
Impact/Purpose:
to present information
Description:
Polychlorinated biphenyls (PCBs) are toxic and recalcitrant environment pollutants that are prevalent in nation's submarine sediments. PCBs bioaccumulate and progressively move up the food chain to reach humans posing serious health hazards. Today, fish consumption is a major route of PCB exposure. Newborns are at risk by exposure through their mother's milk and fetuses from their mother's blood resulting in premature births, lower birth weights and delayed neuromuscular development. It is estimated that the existing PCB wastes will cost more than $394 billion to be incinerated and land filled. Numerous approaches tested for PCB remediation have met with limited success. Fast evolving redox processes such as Pd/Fe systems have been demonstrated for rapid PCB dechlorination. However, Fe corrodes spontaneously in air, forcing surface-pretreatment and synthesis and storage in anaerobic conditions. Mg has unique corrosion properties allowing ambient synthesis, storage and application. Its high oxidation potential (2.372V vs. 0.44V of Fe), natural abundance, low cost' and environmentally friendly nature further strengthen its candidature as substrate for corrosion-based dechlorination systems. This study was conducted to assess the dechlorination potential of such Pd/Mg bimetallic systems. A simple wet-chemistry procedure was developed to synthesize Pd/Mg particles with 0.11 % to 1.62% Pd content and nano-scale Pd-islands (50-100 nm) as determined by inductively coupled plasma spectrometry (ICP-AES), X-ray diffraction (XRD) and environmental scanning electron microscopy (ESEM). Aqueous 2-ClBP matrices were effectively degraded using these particles, the dechlorination kinetics showing linear dependence on the total Pd content. The pH profile obtained with varying bimetallic content led to useful insights into the unique behavior of Mg surface. A carbon mole balance showed 85-105% recoveries. Performance of the Pd/Mg particles in PCB spiked clays and sediment suggests that they may work well in such systems. A mechanism for PCB dechlorination in Pd/Mg systems was also proposed.