Poly (7-oxanorborn-2-ene-5,6-dicarboxylate)-coated silica prepared by ring-opening metathesis polymerization for the selective enrichment of radioactive lanthanides

Block-co-polymers of norborn-2-ene and 7-oxanorborn-2-ene-5,6-dicarboxylate were prepared by ring-opening metathesis polymerization and used for the preparation of poly(norborn-2-ene)-block-(7-oxanorborn-2-ene-5,6-dicarboxylate)-coated silica materials. These sorbents were used for the selective extraction of lanthanides. The coated silicas exhibit an extraordinary good pH stability, are hydrophilic and therefore easily wetable by water alone and show high extraction efficiencies for lanthanides. The use of 200-400 mesh (20-40 mu m) materials guarantees a facile handling in terms of back pressure. The extraction efficiencies of the new material for radioactive lanthanides were determined over a concentration range of 20 ng/l-250 mu g/ml by the enrichment of Pm-147 and Eu-152 from aqueous solutions. Breakthrough curves, the loading characteristics at different pH-values as well as recoveries for both Pm-147 and Eu-152 were determined by beta liquid scintillation counting. The optimum pH for lanthanide extraction was found to be in the range of 3.5-5.5. The high extraction selectivity of the new sorbents for lanthanides was confirmed by recovery, HPLC as well as ICP-OES experiments. These investigations revealed that the retention of potentially interfering metal ions such as Mg2+, Ca2+, Ba2+, Mn2+, Co2+, Ni2+, Al3+, Fe3+, Zn2+ by the new sorbent was less than 5% in all cases. Actinides such as UO22+ and Th4+ are quantitatively coextracted by the resin, yet do not interfere in beta liquid scintillation counting. (C) 1999 Elsevier Science B.V. All rights reserved.