Factors affecting the position of Y and actinides(III) with respect to lanthanides in the NH4SCN - Adogen-464SCN extraction system

The extraction of La, Eu, Lu, Y, Am and Cf by Adogen-464SCN from ammonium thiocyanate solutions has been studied as a function of extractant and thiocyanate concentration. It has been shown that the degree of complex formation in the aqueous phase decreases across the lanthanide series and increases between Am and Cf, whereas in the organic phase it increases for both series. With respect to complexation in the aqueous phase, Y is midway between Eu and Lu, Am is near to La, and Cf is a pseudolanthanide lighter than La. On the other hand, it has been shown that with respect to complexation in the organic phase Am and Cf are out of the heavy end of the lanthanide series, and Y is near to La. Because the organic term prevails, the distribution ratio increases in the order La < Y < Eu < Lu < Am < Cf, except for very high concentrations of thiocyanate ions, where Am and Cf are less extrated than Lu. (orig.)