(661a) Magnetic Metal Extraction: From the Ml Scale to the m3 Scale

Magnetic filtration provides an efficient way to control large liquid volumes with a small amount of a specific reagent. At present, the lack of sufficiently stable nanomagnets has limited the magnetic filtration to routine processing in biochemical separations, particularly in diagnostics. Unfortunately these high-price applications are limited to water and neutral pH as the present oxide-based nanomagnets have a poor stability and low binding capacities. Recently we prepared metallic nanoparticles with a graphene-like carbon coating of 1-2 nm by reducing flame spray synthesis [1,2]. This coating protects the metal nanoparticles from oxidation, against dissolution in acids and it allows the introduction of covalently bound functional groups via diazonium chemistry [3] or physical adsorption, giving access to organic chemistry as a method to design the particle surface. The functionalized magnetic particles represent a promising modular platform for removing a wide range of contaminants. This presentation will show the high efficiency of the coated magnetic nanoparticles in heavy and noble metals ions extraction from acidic aqueous solutions (>95%) even if they are present at very low concentrations (ppb level; nanogram per gram solution) [4,5]. Our most recent results show the applicability of the magnetic particles in large volume (m3-scale) even without external stirring (diffusion and sedimentation) [6]. The attachment of chelating agents on the carbon layer of the particles allows us to selectively target and selectively bind the desired metal. The low costs and particle stability favor this preparation method and material for large-scale separation application of metal ions in ultra low concentrations. Finally a theoretical comparison of a standard chromatography process with a magnetic separation on the level of the energy consumption and the required extraction time for large volume will also be presented. [1] R. N. Grass, W. J. Stark, J. Mater. Chem. 2006, 16, 1825. [2] R. N. Grass, M. Dietiker, R. Spolenak, W. J. Stark, Nanotechnology 2007, 18, 035703. [3] R. N. Grass, E. K. Athanassiou, W. J. Stark, Angew. Chem. Int. Ed. 2007, 26, 4909. [4] M. Rossier, F. M. Koehler, E. K. Athanassiou, R. N. Grass, B. Aeschlimann, D. Günther, W. J. Stark , J. Mater. Chem. 2009, 19, 8239-4. [5] F.M. Koehler, M. Rossier, M. Waelle, E.K. Athanassiou, L.K. Limbach, R.N. Grass, D. Günther, W.J. Stark, Magnetic, Chem. Commun. 2009 , 32, 4862-4. [6] M. Rossier, F. M. Koehler, E. K. Athanassiou, R. N. Grass, M. Waelle, K. Birbaum, D. Günther, W. J. Stark, in preparation.