EPA Nanotechnology and the Environment ... - Mechatronics

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Nanotechnology and the Environment: Applications and Implications STAR Progress Review Workshop Section 3. Remediation Remediation - Technologies to effectively remediate environmental pollutants. Cost-effective remediation techniques also pose a major challenge for the EPA in the development of adequate remedial techniques that protect the public and safeguard the environment. EPA supports research that addresses new remediation approaches that are more effective in removing contamination in a more cost-effective manner than currently available techniques. Substances of significant concern in remediation of soils, sediment, and groundwater, both because of their cancer and non-cancer hazards, include heavy metals (e.g., mercury, lead, cadmium) and organic compounds (e.g., benzene, chlorinated solvents, creosote, toluene). Reducing releases to the air and water, providing safe drinking water, and reducing quantities and exposure to hazardous wastes also are areas of interest. The Office of Research and Development’s National Center for Environmental Research 41
Nanotechnology and the Environment: Applications and Implications STAR Progress Review Workshop Membrane-Based Nanostructured Metals for Reductive Degradation of Hazardous Organics at Room Temperature Dibakar Bhattacharyya 1 , Leonidas G. Bachas 1 , and Stephen M. C. Ritchie 2 1 University of Kentucky, Lexington, KY; 2 University of Alabama, Tuscaloosa, AL Abstract The overall objective of this project is the development and fundamental understanding of reductive dechlorination of selected classes of hazardous organics by immobilized nanosized metal particles (single and bimetallic systems) in ordered membrane domains. This integrated research will examine nanoparticle synthesis in a membrane domain, the role of metal surface area and surface sites, the potential role of ordered nanometal domains in membranes, membrane partitioning, and reaction kinetics with the main emphasis on obtaining highly enhanced dechlorination rates and selectivity from dilute aqueous solutions. The overall hypothesis to be tested is that nanosized (< 50 nm) zero-valent metal domains can be created in an ordered membrane matrix by the use of novel, polypeptide-based biomolecules with helix-coil forming ability or by di-block copolymers. The specific objectives are hypothesis based and will lead to greater insight into hazardous organics dechlorination by providing a highly flexible membrane platform containing nanosized metals. Some of the main hypotheses to be tested include: use of polyfunctional metal binding ligands (such as polyamino acids [PAA]) will lead to high loadings of nanosized reactive metals in ordered membrane domains; PAA’s proven helix-forming ability will lead to ordered zero-valent metal entrapment for potential dechlorination selectivity; dissolved metals (a consequence of dechlorination reactions) can be recaptured in these membranes and thus reused; use of block copolymers will lead to the development of very small size and mono-disperse nanoparticles; and membrane partitioning of chlorinated organics will lead to high reaction rates and selectivity. The approach for this project is to examine immobilized nanostructured metals for dechlorination of hazardous organics. The uniqueness of the project is that, in contrast to literature reported data, membrane partitioning and in situ synthesis of nanoparticles in a membrane phase will provide highly enhanced dechlorination rates (200 to 1,000- fold) and selectivity. This project will establish the role of selected nanoscale particles (Fe, Zn, Pd, selected bimetallic systems) in membrane platforms, rate of dehalogenation reactions, and selectivity for the formation of particular ratecontrolling intermediates, and determine the effects of nanoparticle surface area/chemistry and membrane partitioning. Significant efforts will be placed on the degradation of TCE to its intermediates, as well as the degradation of selected chlorinated aromatics. The specific organic degradation studies in dilute solutions will include: TCE and intermediates such as cis-and trans-DCE (with Fe and Zn), mono- /dichlorophenol (bimetallic systems), and 1,2 dichloro- and 1,2,4 trichlorobenzenes (M 0 - Pd nanoparticles). Because the reductive dechlorination results (in metal particle dispersed solution phase) of some of these compounds are available, direct quantitative comparisons of these membrane-based nanometal systems would be possible. The development of the proposed membrane-based nanostructured metals synthesis for reductive dechlorination of various hazardous organics will provide a novel technique for the rapid and selective degradation of hazardous organics at room temperature. The development of this technology will have a significant impact on the role of nanostructured materials in the environmental field for current and future needs. The fundamentally new technique for creating environmentally applicable nanoparticles in an ordered fashion by immobilization in a membrane matrix provides a versatile platform to address diverse needs in both industrial manufacturing and remediation. Kinetic modeling and correlations with molecular descriptors should establish an excellent foundation for fundamental understanding of nanotechnology-based reaction systems. The additional benefits of this work will lead to reduction of materials usage and miniaturization of dechlorination reactor systems by more efficient use of metals and selectivity. The Office of Research and Development’s National Center for Environmental Research 43
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