Membrane-Based Nanostructured Metals for Reductive Degradation of Hazardous Organics

This proposal addresses the rational design of highly effective, reductive degradation schemes from dilute solutions containing selected chlorinated ethenes and aromatics as model compounds using membrane-based nanostructured metals in ordered domains. Specifically, nanosized (less than < 50 nm) zero-valent metal domains will be created in an ordered membrane matrix by the use of novel, polypeptide-based assemblies with helix-coil forming ability or by di-block copolymer membranes with ordered lamellar domains. The Approach will involve the testing of various hypotheses, including: use of polyfunctional metal binding ligands (such as, polyamino acids) will lead to high loadings of nanosized reactive metals in ordered membrane domains; the helix-forming ability of polypeptides will lead to ordered zero-valent metal entrapment for potential dechlorination selectivity; dissolved metals (a consequence of dechlorination reactions) will be recaptured in these membranes and thus reused. The specific experimental goals will establish the role of selected nanoscale particles (Fe, Zn, selected bimetallic systems) in membrane platforms, the rate of dehalogenation reactions, the selectivity for the formation of particular rate-controlling intermediates, as well as determine the effects of nanoparticle surface area/chemistry and membrane partitioning. In addition, the experimental approach will use block copolymers (with hydrophilic and hydrophobic domains) for the development of very small sized and mono-dispersed nanoparticles (4 to 5 nm) for more highly enhanced dechlorination efficiency than reported in the literature for conventional solutionphase experiments. The proposed research is expected to have significant positive impact on pollution remediation through compact and flexible dechlorination technology development with high reaction rates at room temperature, significant reduction of metals usage, waste minimization through possible recovery of nonchlorinated products (e.g., ethylene from chloroethenes), and improvement in water quality. The proposed research will allow the miniaturization of dechlorination systems through the use of nanostructured, immobilized materials. The expected reduction in reaction half-life, from days to minutes, by the use of nanostructured materials will have significant impact in the area of environmental remediation.