371. Solvent-extraction of septivalent rhenium. Part I. Heterogeneous equilibria in the system, aqueous nitric acid–potassium perrhenate–tributyl phosphate

Abstract

The extraction of septivalent rhenium into tributyl phosphate from aqueous nitric acid has been investigated as a function of solvent concentration in the organic, and nitric acid concentration in the aqueous phase, the rhenium concentration being kept constant. The method of continuous variations has been applied to follow the formation of the extractable rhenium compound. The results revealed that perrhenic acid was the only extractable species. The solvent-dependencies have been found to be of the direct fourth-power. The mass-action effect and the anti-synergic interaction between nitric and perrhenic acid have been used to interpret the extraction mechanism involved. An attempt has been made to calculate the formation constant of perrhenic acid tetrasolvate.DURING work in this laboratory on solute-solvent interactions in heterogeneous ternary systems containing aqueous mineral acids and tributyl phosphate? an attempt has been (a)

The Solvent Extraction Behavior of Technetium

“…This behavior is very similar to that of the analogous KRe0 4 system, which has been more thoroughly investigated [12,13]. Under identical conditions, the distribution coefficient of technetium is about 1.5 to 2.5 times that of rhenium, however.…”

“…Similar results have been found previously for both pertechnetate [6] and perrhenate [13], though over a much smaller range of experimental conditions. The validity of these slopes as a measure of solvation numbers has been subject to some debate [12,14], but the constancy of the slopes over the wide range of TBP concentrations, acid concentrations, and temperatures shown in these experiments argues strongly for the accuracy of the method in this case. It is possible to correct the TBP concentration in the organic phase at 25 °C to account for the amount of TBP that is complexed with HN0 3 and hence unavailable to extract technetium [7 ].…”

The Solvent Extraction Behavior of Ruthenium I - The Nitric Acid-Tri-n-Butyl Phosphate System

“…5 that equilibrium has been reached for this case. Though the validity of the method has been subject to some debate [19,20], the slope of such a plot is often used as a method of obtaining the solvation numbers of complexes entering the organic phase [13,17] …”

Solvent Extraction of Tc(VII) and Re(VII) from Nitric Acid Solution with the Mixture of CMPO and TBP

“…Therefore, the donor groups of CMPO and TBP have been considered to be coordinated through hydrogen bonding to the oxygen atoms of HTCO4 [7,18], Accordingly, the extraction mechanisms of the Tc-CMPO and Tc-TBP systems are considered to be almost the same. On the other hand, the solvation number of two for CMPO, differs from that for TBP, which is three [2,4,6,7,12,13] or four [5,8]. If the number of coordination sites between HTCO4-CMPO and HTCO4-TBP is the same, at least one CMPO should behave as a bidentate extractant [20] in order to compensate for the lack of solvation number.…”

“…Furthermore, in present nuclear fuel reprocessing plants, Tc as impurity can cause a significant problem with the extraction of U and Pu. In this regard, the solvent extraction behavior of Tc [1-7, 12, 13] and Re [8][9][10][11][12][13] by using TBP has been investigated. Transuranium elements were found to be effectively separated from acidic nuclear wastes by the TRUEX process [14] using the mixture of CMPO and TBP, which was developed at Argonne National Laboratory.…”