Novel Bis(diphenylcarbamoylmethylphosphine oxide) Ligand for Effective Extraction of Actinides and Lanthanides from Nitric Acid Solutions

A novel polydentate neutral organophosphorus ligand N,N’-dicyclohexyl-N,N’-bis(diphenylphosphinoylacetyl)urea 1 containing two Ph2P(O)CH2C(O)N(cyclo-Hex)- bidentate moieties connected by a carbonyl group through amide nitrogen atoms was studied as an extractant for U(VI), Th(IV) and lanthanides(III) ions from HNO3 solutions into molecular diluents and ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. The influence of composition of aqueous and organic phases on the extraction efficiency was elucidated and stoichiometry of the complexes extracted was determined. Slope analysis indicates that the ligand 1: metal ratio in the extracted complexes in ionic liquid is less than that in 1,2-dichloroethane. The extraction efficiency of bis-CMPO 1 towards U(VI), Th(IV) and lanthanides(III) increased significantly in the presence of ionic liquid. Bis-CMPO ligand 1 in ionic liquid was found to possess a higher extraction efficiency towards U(VI), Th(IV) and lanthanides(III) ions than its mono analog diphenyl-(N,N-dibutylcarbamoylmethyl)-phosphine oxide 2. The role of Tf2N− anions in increasing the efficiency of Ln(III) extraction in the presence of an ionic liquid is discussed.