Tethered Ligand Nanotechnology Composites Enable High Throughput Metal Separations
R.H. Hammen, J.P. Hammen and C.R. Hammen
ChelaTech, Inc., US
composites, interface, polymers, ligands
The valuable metal mining industries have technical challenges of separating small quantities of desired metal species from large masses of lower value ions. The cost and hydrometallurgical performance of conventional resin and activated carbon columns are compromised by sluggish adsorption/desorption kinetics, caused by rate-limiting transport of metal ions through the stagnant boundary layer at the solid-liquid interface. Slow kinetics require the use of large columns with long residence times for metal binding and desorption. We report the properties of nanostructured metal-selective adsorption composites, having metal binding ligands tethered in the active solution transport zone of the matrices. Kinetic measurements of copper ion binding by tethered chelating agents show the ligand-copper binding reaction occurs with residence times of a few seconds and is essentially independent of flow rate. The practical utility of the rapid equilibration kinetics is demonstrated by the separation of nickel and copper ions in a tethered iminodiacetic acid ligand composite. One passage of a copper/nickel solution through a tethered ligand composite resolves the ions into highly purified nickel and copper fractions. Economic benefits versus currently used processes include lower capital cost, lower energy usage during operations, higher recovery rates of desired target metals, and substantially lower environmental impacts.
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Nanotech 2006 Conference Program Abstract