GB1031194A - Improvements in the fractionation of aqueous solutions - Google Patents

Abstract

A mixture of Pu/U/fission products, or a mixture of Fe, Co, and Ni are separated in solution by a graded concentration multi-stage extraction system. There is set up an array of vessels containing batches of an organic extractant for the species to be separated, or a solution of such extractant in an inert diluent, e.g. tributyl phosphate in CCl4 for U/Pu and trioctyl phosphine oxide in CCl4 for Fe, Co, Mi. The materials to be separated are in aqueous mineral acid solution, and a second series of vessels are prepared containing batches of aqueous mineral acid, each batch containing acid of different concentration, the concentration varying stepwise along the aqueous series, the final vessel of this series preferably containing water. The first aqueous batch, i.e. that containing the materials to be separated is mixed with the first batch of organic extractant, allowed to settle and separated, the aqueous layer is then shaken with the second organic batch, and separated and is then shaken in turn with all the remainder of the organic batches. The first aqueous batch is followed through the organic series by the second aqueous batch, i.e. an aqueous acid solution, and the third and subsequent aqueous batches until each aqueous batch has been treated with each organic batch. The net result of this procedure is that upon completion, the organic batches are uncontaminated and may be used again, whilst the mixture of solutes is so distributed through the aqueous series that each solute occupies almost exclusively a particular range of batches in the aqueous series and may thus be easily separated, e.g. 23 batches of aqueous nitric acid used in the separation of U/Pu/fission products batches 1-5 contained almost all the fission products, Pu 239 was contained in batches 6-10 and U was contained in batches 10-20, and similar results were obtained for Fe, Co and Mi using HCl solutions. If desired the concentration of extractant may be varied stepwise from batch to batch in the organic series.ALSO:In a graded concentration multistage extraction system, e.g for a mixture of Pu/U/fission products, or a mixture of Fe, Co, and Ni, there is set up an array of vessels containing batches of an organic extractant for the species to be separated or a solution of such extractant in an inert diluent e.g. tributyl phosphate in CCl4 for U/Pu and trioctyl phosphine oxide in CCl4 for Fe, Co, Mi. The materials to be separated are in aqueous mineral acid solution, and a second series of vessels are prepared containing batches of aqueous mineral acid, each batch containing acid of different concentration, the concentration varying stepwise along the aqueous series the final vessel of this series preferably containing water. The first aqueous batch i.e. that containing the materials to be separated is mixed with the first batch of organic extractant, allowed to settle and separated, the aqueous layer is then shaken with the second organic batch and separated, and is then shaken in turn with all the remainder of the organic batches. The first aqueous batch is followed through the organic series by the second aqueous batch, i.e. an aqueous acid solution, and the third and subsequent aqueous batches until each aqueous bath has been trated with each organic batch. The net result of this procedure is that upon completion, the organic batches are uncontaminated and may be used again, whilst the mixture of solutes is so distributed through the aqueous series that each solute occupies almost exclusively a particular range of batches in the aqueous series and may thus be easily separated e.g. of 23 batches of aqueous nitric acid used in the separation of U/Pu/fission products batches 1-5 contained almost all the fission products, Pu 239 was contained in batches 6-10 and U was contained in batches 10-20, and similar results were obtained for Fe, Co and Ni using HCl solutions. ]If desired the concentration of extractant may be varied stepwise from batch to batch in the organic series.