Synthesis of Nanostructured Bimetallic Particles in Polyligand-Functionalized Membranes for Remediation Applications

The creation and development of nanosized materials have brought important and promising techniques into the field of environmental remediation of chlorinated organics. Extensive studies have been reported on the degradation of toxic chlorinated organics (such as trichloroethylene and polychlorinated biphenyls) with non-immobilized Fe⁰ based bulk/nanoparticles. Work involving reductive dechlorination involved the use of bimetallic (Fe/Ni and Fe/Pd) nanoparticle systems, both membrane-supported and direct aqueous-phase synthesis. The nanosized metals precipitated from solutions are extremely reactive due to their high surface energy, and they usually form aggregates without the protection of their surface. Therefore, immobilization of metal nanoparticles in polymer membrane (such as cellulose acetate, polyvinylidene fluoride (PVDF), polysulfone, chitosan, etc.) media is important from the point of view of reactivity, organic partitioning, preventing loss of nanoparticles, and reduction of surface passivation. Another major advantage of having a polymer domain is that nanoparticles (without causing agglomeration) can be directly synthesized in the matrix. The significant findings of our work are: (i) direct synthesis of bimetallic nanoparticles is possible with controlled diameters <40nm using membrane-based supports derived from polyligand functionalization and ion exchange (polyacrylic acid domain); and (ii) demonstration of complete (with product and intermediates analysis) dechlorination of trichloroethylene (TCE) and selected polychlorinated biphenyls (PCBs) by nanosized metals. The second dopant metal (such as Ni, Pd) plays a very important role in terms of catalytic property (hydrodechlorination) and the significant minimization of intermediates formation. In addition to the rapid degradation (by Fe/Ni) of TCE to ethane, we were also able to achieve complete dechlorination of selected PCBs using milligram quantities of immobilized Fe/Pd nanoparticles in membrane domain.