Evaluation of ovotransferrin-matrix metal-affinity metalloprotein chromatography for Pu(IV) separations

Metal-Affinity metalloprotein chromatography has been suggested to have potential for selectively removing actinides from solution. To evaluate this potential, characterization of Pu(IV) and Fe(III) binding to an ovotransferrin-Sepharose(TM) 4B matrix, with oxalate and carbonate synergistic anions, was performed. Metal binding capacity was determined for metal concentrations ranging from 2 x 10(-6) to 1 x 10(-3) M Fe(III) and 2.9 x 10(-5) to 2.6 x 10(-4) M Pu(IV), where both metals were added as a solution of 10:1 nitrilotriacetic acid:metal. Metal binding capacity was also determined over the pH range 3.0 to 9.2. The metal binding properties of the immobilized ovotransferrin were found to differ from those reported for free-protein studies. Distribution coefficients were low: for metal solution concentrations of 0.02, 0.04, 0.10, and 0.20 mM, coefficients were 540. 180. 23. and 12 mL/g for Fe(III) and 20, 12, 7.2, and 6.0 mL/g for Pu(IV), respectively. The capacity of the material was less dependent on pH than expected, varying by only two mumoles metal/g matrix for both Fe(III) and Pu(IV) over the pH range of 4.2 to 9.5. This study illustrates limitations of metalloprotein chromatography for Pu(IV) separation.