Actinides Extractability Trends for Multidentate Diamides and Phosphine Oxides

Diamides and phosphine oxides having many types of central frames were synthesized and employed in order to determine the behavior of the actinides (An)(III), (IV), (V) and (VI). Diamides synthesized here have two, three, or four donor atoms of amidic and etheric oxygen (nitrogen or sulfur, instead) atoms in their central frames, namely the extractants can work in bi-, tri-, and tetradentate modes. Di-phosphine di-oxides ((Bis(diphenylphosphoryl)methane (BDPPM) and bis(diphenylphosphoryl)ethylene (BDPPE)), carbamoylmethylphosphine oxide (octylphenyl-N,N-diisobutyl-carbamoylmethylphosphine oxide (CMPO)) are used as the representative actinide extractants. Eu(III), Th(IV), U(VI), Np(V), Pu(IV) and Am(III) ions in perchloric acid were extracted into nitrobenzene or n-dodecane. Measurement of the D value at different extractant concentrations gave information on the extraction reaction and extraction ability. From the present work, the best extractant is BDPPM, due to the strong affinity provided P=O group and its bidentate form resulting in six-membered ring chelation. However, this extractant has too low a solubility in n-dodecane. From the properties required for application, e.g., high solubility in n-dodecane, easy organic synthesis, gasification by combustion and high actinide extractability, into consideration, diglycolamide (DGA) is a promising extractant for radioactive waste treatment.