Evaluation of several multiple diglycolamide-functionalized calix[4]arene ligands for the isolation of carrier free 90Y from 90Sr.

Several diglycolamide-functionalized calix[4]arenes containing four and eight diglycolamide (DGA) moieties were evaluated for their relative extraction efficiencies towards Y(III) and Sr(II). Ligands containing four DGA units with n-propyl, iso-pentyl, and n-octyl groups at the amidic N atom adjacent to the calix[4]arene skeleton showed efficient extraction of Y(III) from 3M HNO3. The extraction of Sr(II) was poor in all cases in the entire acidity range (0.1-6M HNO3) studied. The ligands with a hydrogen atom and an n-propyl group at the concerning amidic N atom showed a very high separation efficiency as reflected in separation factor (S.F.=DY/DSr) values in the range of 10(5)-10(6). A method was developed for the separation of carrier-free (90)Y from a (90)Y-(90)Sr mixture involving consecutive extraction-stripping cycles. The product purity was checked using half-life measurements. Two consecutive cycles of extraction and stripping were found to be sufficient for obtaining pure (90)Y. The results obtained in the present studies were compared with those obtained previously using analogous ligands such as TODGA (N,N,N',N'-tetraoctyl diglycolamide), T2EHDGA (N,N,N',N'-tetra-2-ethylhexyl diglycolamide), and PC-88A (bis(2-ethylhexyl) phosphonic acid).