I&EC 167 |
| Recently acknowledged threats involving the potential deliberate release of radionuclides into local environments by terrorist activities now prompt new concerns and the need for improved methods of removing internally deposited radionuclides. To date, only a few standard treatments are available for certain radionuclide intakes. In this project, we are investigating the potential of readily available chitosan biomaterials as sequestering agents for radionuclides and toxic metals in humans. Resembling cellulose in molecular form, chitosan is composed of linear polymeric molecules of β-(1-4) linked amino-D-glucose units. Due to amino functionality, the complexation behavior of chitosan is pH-dependent. Chitosan is a weak base and it has a pKa value for the D-glucosamine base unit of about 6.2 – 7.4. In this work, we investigated the pH speciation behavior of glucosamine and chitosan polysaccharide and their affinity to transition and f-block metals. Complexation behavior of representative metal ions, including Co(II) and Nd(III) among others, was systematically studied in 5 – 11 pH range by UV-vis spectrophotometry combined with potentiometric titrations. Formation of the mixed hydroxy-glucosamine metal complex species was suggested. This complexation mechanism, namely ligand-controlled hydrolysis, helps to keep these susceptible-to-hydrolysis metal ions in solution and prevents their precipitation at elevated pH. Formation of the polynuclear Nd(III) species in solution with and without glucosamine or chitosan was probed by x-ray absorption fine structure (XAFS) spectroscopy. |
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Separation of f-Elements, Sponsored by Separation Science and Technology Sub-Division
9:00 AM-12:00 PM, Thursday, 14 September 2006 Moscone Center -- Room 250, Oral
Division of Industrial & Engineering Chemistry |