SEPARATIONS BY SOLVENT EXTRACTION WITH TRI-n-OCTYL-PHOSPHINE OXIDE

Abstract

The Subcommittee on Radiochemistry Is one of a number of subcommittees working under the Committee on Nuclear Science within the National Academy of Sciences-National Research Council. Its members represent government, industrial, and university laboratories in the areas of nuclear chemistry and analytical chemistry. The Subcommittee has concerned itself with those areas of nuclear science which Involve the chemist, such aa the collection and distribution of radiochemical procedures, the establishment of specifications for radiochemlcally pure reagents, availability of cyclotron time for service irradiations, the place of radiochemistry in the undergraduate college program, etc. This series of monographs has grown out of the need for up-to-date compilations of radiochemical Information, procedures, and techniques. The Subcommittee has endeavored to present a series which will be of maximum use to the working scientist and which contains the latest available information. Each monograph collects in one volume the pertinent information required for radiochemical work with an Individual element or with a specialized technique. An expert in the particular radiochemical technique has written the monograph. The Atomic Energy Commission has sponsored the printing of the series. The Subcommittee is confident these publications will be useful not only to the radlochemist but also to the research worker in other fields such as physics, biochemistry or medicine who wishes to use radiochemical techniques to solve a specific problem.

Features of the Thermodynamics of Trivalent Lanthanide/Actinide Distribution Reactions by Tri-n-octylphosphine Oxide and Bis(2-ethylhexyl) Phosphoric Acid

“…The two-phase equilibrium expressions for the extraction of trivalent metal ions and nitric acid by TOPO can be written as , normalM 3 + false( normala false) + 3 NO 3 − false( normala false) + 3 TOPO false( normalo false) ⇄ normalM false( NO 3 false) 3 false( TOPO false) 3 ( o ) normalH + false( normala false) + NO 3 − false( normala false) + n TOPO false( normalo false) ⇄ false( HNO 3 · n TOPO false) false( normalo false) where (a) and (o) represent the aqueous and organic phases, respectively. Typically n = 1, but at high acid concentrations and high ionic strength n = 0.5 suggesting a (2HNO 3 ·TOPO) (o) complex . The extraction constant can be derived from eq by arranging the equilibrium expression: K ex = [ M ( N O 3 …”

“…Unlike the straightforward metal ion extraction system with HDEHP (i.e., eq ), neutral solvating extractant systems require multiple reactions for metal ion transport to the organic phase (e.g., eqs and ). ,, As such, a new two-phase calorimetric methodology was developed to ensure direct measurement of the heats associated with metal ion partitioning only. It was essential to eliminate the coextraction of HNO 3 by TOPO (and associated heats) during the calorimetric titration experiments.…”

“…The strength of TOPO provides a pertinent platform for conducting fundamental studies of this class of extractants, i.e., determination of thermodynamic parameters, Δ G , Δ H , and Δ S , for the biphasic extraction of trivalent metal ions by a neutral solvating extractant. Previous reports − have investigated the fundamental properties of Ln(L) 3 and An(L) 3 extraction by TOPO from various aqueous media, where L = Cl – , NO 3 – , ClO 4 – , or SCN – . Since TOPO use is restricted by solubility in nonpolar diluents, significant research has been performed studying TOPO in synergistic extraction systems designed to separate trivalent lanthanides and trivalent actinides. − In synergistic extraction systems, enhanced extraction of target metal ions is observed through employing two metal ion extractants.…”

Spectrophotometric determination of trace uranium in plutonium nitrate and oxide with 2-(2-pyridylazo)-5-diethylaminophenol

“…Since TOPO extractions [3] were compatible with the spectrophotometric method and since TOPO had been used for the separation of U from Pu for X-ray determinations [6,9] it was decided to investigate this approach for analyzing trace U in Pu. The procedure was calibrated by adding U standards directly to the 4M HCl-2M NH 2OH·HCl matrix and extracting with 2 ml of TOPO in cyclohexane and proceeding as described In order to determine the effect of plutonium on the procedure, a 108.9 vg uranium spike was added to varying quantities of a 282 g/liter Pu(N03)4 solution in the extraction matrix.…”

Metal nitrate complexes with tributyl phosphate and with trioctyl phosphine oxide

“…Most of the extraction data for solutes in tri-n-octyl phosphine oxide, (CgH^y )^P0, were given by White and Ross (56). They also determined the particular complexes involved between tri-n-octyl phosphine oxide and various nitrates and chlorides using the slope method.…”