EXTRACTION OF LANTHANIDE(III) AND URANYL(VI) FROM NITRIC-ACID SOLUTION BY N,N'-DIMETHYL-N,N'-DIBUTYLMALONAMIDE

The extractive properties of N,N'-dimethyl-N,N'-dibutylmalonamide (DMDBMA) and the loading capacity of extraction solvents containing DMDBMA for lanthanide(III) and uranyl(VI) ions in nitric acid solution were investigated. The dependence of the distribution ratio on the concentration of nitric acid shows that DMDBMA has an ability to extract uranyl(VI) ion, while the extracting capacity for lanthanide(III) ions is not enough for the application in practice. The slope analyses for La(III), Nd(III), EU(III) and UO2(VI) ions in 3.0 M HNO3 solution exhibit a straight line with the slope of 2.9, 2.9, 2.1 and 2.3, respectively. It was found that these extractions are an exothermic reaction with the enthalpy changes of approximate -20[kJ/mol]. The solubilities of DMDBMA into various diluents were related with the Hildebrand's solubility parameter, delta, the Kamlet-Taft's polarity parameter, pi*, and the Gutmann's acceptor number, AN, of the diluent. The loading percentages of DMDBMA with Nd(III) and UO2(VI) increase with the increase in polarity of the diluent. Moreover, concerning the Nd(III) extraction from nitric acid solution, the diluents with a high polarity have the higher D-Nd than those with a low polarity. This is probably due to the stabilization of the polar group,N+-C=O-, of DMDBMA by interacting with the high polar diluent.