EXTRACTION OF TRIVALENT AND TETRAVALENT ACTINIDES WITH DIHEXYL N,N-DIETHYLCARBAMOYLMETHYL PHOSPHONATE (DHDECMP) AND TBP FROM NITRIC-ACID SOLUTIONS

Extraction of trivalent (Pu3+, Am3+, actinides and Eu3+, a representat ive of lanthanides) and tetravalent (Np4+ and Pu4+) actinides has been studied with dihexyl N,N-di-ethylcarbamoylmethyl phosphonate (DHDECMP ) in combination with TBP in benzene from 2M nitric acid. The stoichio metries of the species extracted were found to be M(NO3)3 . (3 - n) TB P . n DHDECMP (for trivalent ions) and M(NO3)4 . (2 - n) TBP . n DHDEC MP (for tetravalent ions) by the slope ratio method. The extraction co nstants evaluated (from the distribution data) indicate that for tetra valent ions (with solvation number two) the extraction constant increa ses when TBP (Kh = 0.17) molecules are successively replaced by more b asic DHDECMP (Kh = 0.34) molecules. However, for trivalent ions (with solvation number three) when TBP molecules are totally replaced by DHD ECMP molecules stereochemical factors appear and instead of increase, a substantial decrease in extraction constants is observed for Eu3+ an d Am3+, a lesser decrease being observed for Pu3+ (larger ion).