The use of dioctyl phosphoric acid extraction in the isolation of carrier-free 90Y, 140La, 144Ce, 143Pr, and 144Pr

Tracer-level cerium has been oxidized to the tetravalent state and shown to be preferentially extracted from a 10 M HNO3 aqueous phase into a 0·75 M, or 0·30 M, solution of di(2-ethyl hexyl) orthophosphoric acid in n-heptane. In this system the ratio of the K for Ce(IV) to that for Ce(III) is greater than 106, and the K for Ce(IV) is much greater than that for any trivalent lanthanide. This system has been utilized to purify 144Ce with respect to lanthanide contaminants, including its 144Pr daughter, and to prepare a highly-purified gross sample of natural cerium for neutron bombardment in the preparation of 143Pr. It has been used also in the isolation of 143Pr and 144Pr products for tracer studies and for half-life determinations. A decontamination factor, with respect to the parent 144Ce, greater than 107 was obtained for a 144Pr sample isolated and prepared for counting in a period of less than 10 min. Other di(2-ethyl hexyl) orthophosphoric acid systems employing dilute HCl or HNO3 as the opposing phase have been used for separating 90Y from its 90Sr parent and for separating 140La from its 140Ba parent and from contaminant 90Sr90Y. Decontamination factors greater than 107 have been obtained in both separations, the total processing times being less than 15 min. The following new half-life values have been obtained: 90Y, 63·97 ± 0·1 hr; 140La, 40·27 ± 0·05 hr; 143Pr, 13·59 ± 0·04 day; and 144Pr, 17·27 ± 0·04 min.