Separation Factors in the Extraction of Thiocyanatolanthanoids(III) with Trioctyiphosphine Oxide in Hexane and in Chloroform

Abstract

The extraction behavior of lanthanoids(III) from 1M N_a(SCN, Cl) into hexane containing trioctylphosphine oxide has been examined. The data are explained by assuming LnX₃•3E and LnX₃•4E as being the extracted species. The proportion of LnX₃•4E decreases and that of LaX₃•3E increases from light to heavy lanthanoids. The extraction constants for LnX₃•4E are independent of the lanthanoids, and the constants for LnX₃•3E are dependent on the lanthanoids. The separation factor in the hexane system is much smaller than that in chloroform over the series of lanthanoids. The difference is explained in terms of the different extracted species; the dominant species in hexane is LnX₃•4E in the light lanthanoids, while the dominant species in chloroform is LnX₃•3E over the series.