Experimental And Theoretical Study Of The Extraction Of UO₂²⁺ By Amide Extractant

Solvent extraction studies of UO22+ were carried out using N, N’-dimethyl-N, N’-dibutylmalonamide(DMDBMA), N, N, N’, N’-tetrabutylmalonamide(TBMA), N, N, N’, N’-tetraoctylmalonamide(TOMA), N, N, N’, N’-tetra-n-octyl-3-oxy-dioctlyl glutaramide(TODGA) dissolved in room temperature ionic liquids(RTILs) of 1-alkyl-3-methylimidazolium bis(trifluoromethane)sulfonamide([Cnmim][TNf2], n=4,6,8) and 1-alkyl-3-methylimidazolium hexafluorophosphate([Cnmim][PF6], n = 6 or 8). This work mainly studied that UO22+ was extracted from aqueous solution to ionic liquid by the four ligands. At lower acidity the extraction of UO22+ carried out in RTIL was found to be much more efficient than in the conventional molecular diluents, while this advantage diminishes at higher acidity. The alkyl chain length of the RTILs plays an important role on the extraction performance. The effect of concentration of four kinds of extraction agents and nitric acid on extraction performance was also investigated. The extraction mechanism using RTILs as the diluent was deduced by the slope analysis and extraction experiment and a cation-exchange mechanism at lower acidity and a neutral solvation mechanism at higher acidity were proposed. The complexes of UO22+ with the three malonamide ligands were investigated using density functional theory in terms of geometry, Mayer bond order(MBO), binding energy, interface exchange reaction, and electron density at BCP. The computational data complement the experimental study by providing detailed information at the molecular level.