Selective uptake properties of metal ions by hybrid microcapsules enclosed with TBP

The granulation of TBP extractant is effective for the enhancement of uptake efficiency. The granulation was accomplished by microencapsulating techniques using alginate gel polymers (alginate and alginic acid gel polymers; calcium alginate, barium alginate and nitric alginate (CaALG, BaALG and HALG)). The characterization of hybrid microcapsules was examined by SEM/EPMA, and the uptake properties and the selectivity of various nuclides, Fe(III), Sr(II), Co(II), U(VI) and Pu(IV), were examined by batch methods. A relatively high uptake (%) of Fe(III), Sr(II) and Co(II) above 80% was obtained in the presence of 10^-3 M HNO₃, and the uptake equilibrium was attained within 5 h. The uptake rate of U(VI) and Pu(IV) attained equilibrium within 1 h and 3 h, respectively. At higher HNO₃ concentration ranging from 10^-3 M to 5 M, the uptake (%) of Fe(III), Sr(II) and Co(II) was considerably lowered. In contrast, the uptake (%) of U(VI) and Pu(IV) about 60% was obtained even in the presence of 5 M HNO₃. The uptake of U(VI) for MCs (TBP-CaALG) was governed by the extraction with TBP micro droplets and ion-exchange reaction in the CaALG matrices. Energy dispersive spectra (EDS) showed that U(VI) ions were incorporated into both phases of TBP and CaALG in microcapsules.