Advanced TALSPEAK for separating trivalent actinides and lanthanides

An Advanced TALSPEAK (trivalent actinide-lanthanide separations by phosphorus-reagentextraction from aqueous complexes) concept is being developed that uses2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) to selectively extract trivalentlanthanide (Ln) ions in preference to trivalent actinide (An) ions. The An ions are held in theaqueous phase by complexing with N-(2-hydroxyethyl)-ethylenediamine-N,N',N'-triacetic acid(HEDTA). The primary advantage of the Advanced TALSPEAK system compared to thetraditional TALSPEAK system is that it is much less sensitive to the aqueous solution pH. For thisreason, it is viewed as being much more robust for industrial application. In this paper, wedescribe the basic principles of the Advanced TALSPEAK system, as well as experimentsconducted to explore the sensitivity of the process to minor changes in the process conditions(for example, changes in the pH, the HEDTA concentration, etc.). The latter experimentsshowed that the Advanced TALSPEAK system can be expected to be robust in a plant setting. Aflowsheet has been developed and a counter-current flow test using a surrogate feed isdiscusse