Group separation of the actinides from the lanthanides by anion exchange

Abstract

The separation of the lanthanides from the tripositive actinides has been successfully accomplished by column elution with lithium chloride solutions 10 M or stronger using a moderately cross-linked, strongly basic anion exchange resin at an elevated temperature. Fractionation of the actinide ions into the groups Pu, AmCm, Bk, and CfEs can be obtained during the same column elution. The distribution coefficient D v (defined in terms of the geometric resin bed volume) of representative actinides and lanthanides was investigated as a function of LiCl and H + concentration, temperature, and cross-linkage of the resin, using the column elution technique. In addition, adsorption kinetics were investigated by measurement of americium elution peak half-widths over a range of flow-rates at 25 and 87°C with 2, 8, and 10 per cent DVB resin of several particle sizes. The formation of anionic complexes is markedly influenced by the LiCl and H + concentrations. D v for La, Lu, Am and Cf uniformly decreased by nearly one-fourth when the H + concentration was increased from 0·1 to 1·0 M, while maintaining the chloride ion concentration constant at 10·15 M. Except for deviations observed in the elution order of Gd and Ho and their corresponding actinide homologs, Cm and Es, the elution sequence proceeded in order of increasing atomic number, La being the least strongly adsorbed. Under acceptable operating conditions the ratio D v( Am) D v( La) = 19 .