Calcium isotope separation by band chromatography using 18-crown-6-ether resin

To develop the Ca-48 enrichment process, a feasibility study on a band chromatography was made using 9 M HCl solution and crown ether resin synthesized in porous silica beads. Prior to the chromatographic experiments, distribution coefficients, Kd, of Ca2+ and Sr2+ were measured at different concentrations of these ionic species. The frontal boundary of the chromatography was made by a usual manner of the breakthrough mode of calcium feeding, and the rear boundary was made by introducing strontium as a following ion on the basis of the observed Kd values. It was confirmed that the heavy isotope Ca-48 was depleted in the rear boundary region, while Ca-48 was enriched in the front boundary region. The values of separation coefficient epsilon (= alpha - 1) in three chromatographic operations at different temperatures were observed as 2 x 10(-3) similar to 3 x 10(-3). The separation coefficients observed in the front boundary regions, where Ca-48 was enriched, agreed with those observed in the rear boundary regions, where Ca-40 was enriched.