(93f) Synthesis of Metal Nanoparticles in Various Platforms for Detoxification of Chloroorganics From Water
Zero-valent iron nanoparticles (or bi-metallic iron/palladium particles) used for the dechlorination of hazardous organic groundwater pollutants are produced by reduction of iron ions immobilized on various platforms. These platforms include silica nanoparticles functionalized with sulfonate or poly(aspartic acid), as well as functionalized silica with both hydrophobic and hydrophilic functional groups. Another useful platform is functionalized membranes. The iron nanoparticles are synthesized by reduction with borohydride, and then coated with a secondary metal such as Pd. Alternatively,?green chemistry? reducing agents, such as ascorbic acid can be used to reduce ferrous iron to zero-valent iron particles in the presence of Pd. This allows for the complete synthesis of zero-valent nanoparticles from completely non-toxic starting reagents without the use of surfactants or capping agents. Synthesis results such as extent of platform functionalization, iron loading on platforms, and iron or bi-metallic particle sizes and morphologies are presented. Sulfonate-functionalized silica as a platform results in particles which are rod-shaped showing potential directed growth. However, polyligand functionalized platforms such as poly(aspartic acid) or poly(styrene sulfonate) can achieve higher iron loading. The surface chemistry role of the ascorbic acid on ?green? bi-metallic particles is also discussed. As has been previously shown, zero-valent iron and bi-metallic particles are useful for reduction of chlorinated organic compounds such as TCE. In this study, the platform immobilized nanoparticles may bring additional benefits such as less aggregation and better dispersion of nanoparticles and the ability to achieve multiple functional groups, such as the creation of hydrophobic nanodomains near the active sites of dechlorination reaction. The dechlorination of trichloroethylene (TCE), polychlorinated biphenyls (PCBs), and other chloroorganics by immobilized as well as ?green? particles is presented and compared to previous results obtained from non-immobilized particles. This research is supported by the NIEHS-SBRP program.