Plutonium(IV) Extraction from Nitric Acid Solutions by Mixtures of Long-Chain Ammonium Nitrates

Summary The liquid-liquid extraction of tracer amounts of Pu(IV) from 0.5 and 3 M nitric acid solutions by a mixture A + B, of two quaternary ammonium nitrates of a high molecular weight, or of one such nitrate with a long-chain tertiary amine nitrate in chloroform and in the octanol containing solvents n-dodecane or o-xylene has been studied. The Pu(IV) distribution coefficients D observed are not widely different from the values calculated for D = (DA 1/q + DB 1/q) q where DA and DB represent the Pu(IV) distribution coefficients for each of the components alone, and q denotes the slope value of the extraction curve, log DA vs. log [A]initial. The extracting agents used are: trilaurylamine (TLA), trilauryl-methylammonium nitrate (TLMA) and hexadecyl-dimethyl-benzyl ammonium nitrate (HDDMBA). Thermodifferential molecular weight determinations of quaternary ammonium nitrates and their Th(IV) and U(VI) nitrate complexes in benzene show a higher degree of association for the metal complexes than for the extracting agents. By saturation of solutions of different quaternary ammonium nitrates in benzene with Th(NO3)4 · 6H2O the thorium loading is lower in both light- and heavy organic phase than would correspond with a ratio of two quaternary ammonium nitrate molecules to one thorium atom.