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Applications of Nano Reactive Materials in Remediation of Persistence Organic Pollutants in Sediments and Groundwater - Presentation
Citation:
Al-Abed, S. R. Applications of Nano Reactive Materials in Remediation of Persistence Organic Pollutants in Sediments and Groundwater - Presentation. Presented at Third International Symposium on Environmental Nano Technology (ISENT 07), Gwangju, SOUTH KOREA, October 18 - 19, 2007.
Impact/Purpose:
General Scientific or Technical Work Product
Description:
Remediation of sediments and water contaminated hydrophobic organic chemicals (HOCs) such as polychlorinated biphenyls (PCBs) remains a scientific and technical challenge. PCBs-contaminated sediments are ubiquitous despite the production and use of PCBs was banned in 1979 due to their toxicity and persistence in the environment. Many technologies employing physical, chemical and even biological remediation strategies have been proposed, including dredging, landfilling, incineration, in-situ capping, dechlorination using reactive metals, and bio-decomposition. However, in addition to the high stability of PCBs, their low solubility in water and high affinity to organic substances make it difficult to treat PCBs using conventional methods. The use of reactive zerovalent metals such as iron and magnesium has been well documented to work efficiently for the dechlorination. Metals are oxidized to produce electrons while PCBs are reduced to release chloride ions. Alternatively, the released electrons can produce hydrogen from electrolysis of water, which can be activated and ultimately used to dichlorinate PCB. Two main strategies have been focused to increase the reactivity. Fe and Mg are oxidized more rapidly when attached with less active metals (Pd, Pt, Ni, Ag). Thus, the overall reactivity can be significantly increased by depositing a thin and discontinuous layer (i.e., islands) of noble metals on Fe and Mg surface. Studies also suggested that dechlorination of PCBs is facilitated through Pd-mediated hydrogenation. In addition, dechlorination of PCBs using zero-valent iron/pd (ZVI/Pd) systems can be improved by introducing nanoscale ZVI particles and Pd nano-islands on the ZVI. The small size and high surface to volume ratio of nanoscale Fe make it attractive for PCBs dechlorination, compared to those of conventional micron size Fe. In this presentation, we will address some challenges for the versatile applications of these Fe/Pd and Mg/Pd bimetal systems for the remediation of PCBs-contaminated sediments and soil and discuss some idea and strategies on how the challenges could be resolved by introducing nanotechnological synthesis routes and noble material processing approaches. This includes i) nano-scaling of Pd and Fe particles, ii) immobilization of Fe/Pd bimetals on granular activated carbon for the simultaneous adsorption and dechlorination of PCBs, and iii) introduction of new Mg/Pd bimetal system.