Abstract: The extraction of nitric acid and U(Ⅵ ) from nitric acid solutions with N,N,N',N'-tetrahexylmalonamide (THMA) in toluene has been carried out.The dependences of theextraction distribution ratios on the concentrations of aqueous nitric acid, extractant andsodium nitrate and the temperature have been investigated.The extraction stoichiometry hasbeen established and the structure of the extracted complex was analyzed by IR spectrometry.The extraction constants of nitric acid and U(Ⅳ) with THMA and the reaction enthalpywere calculated.In comparison with the extractability of N,N,N',N'-tetrabutylmalonamide, it shows that increase in the alkyl chain longth lowering the formation of the thirdphase and decreases the extractability of the amides.

Key words: tetrahexylmalonamide, uranium extraction