E.P. Horwitz

Interfacial activity of liquid-liquid extraction reagents—I: Dialkyl phosphorous based acids☆

Gibbs isotherm curves were run for a series of dialkyl phosphoric, phosphonic, and phosphinic acids, most in dodecane against 1 M HNO3 at 25°C. The interfacial areas and minimum concentration of interfacial saturation (Cmin) were correlated against changes in the polar and non-polar parts of these amphipathic molecules. Linear correlations were observed for log Cmin values of the phosphoric acids studied and their acidity constants (pKa) and the log of their metal ion extraction constants (log KS) for Am3+. Effects of changes in solvent and temperature were also studied and are discussed. Proof was found for a monomer/dimer equilibrium in concentrations under 3 × 10−4 M for bis(2-ethylhexyl)phosphinic acid.

The mechanism of interfacial mass transfer of calcium in the system: Di(2-ethylhexyl)phosphoric acid in dodecane-dilute nitric acid

Abstract Through a study of the kinetics and equilibria of the interfacial mass transfer of this system and correlating it with studies of interfacial tension vs concentration data, it has been possible to determine a consistant and revealing mechanism of extraction. This mechanism is as follows: The subscripts A, I and O indicate the environment of the species—the aqueous phase, the interface, or the organic phase. HDEHP is di(2-ethylhexyl)phosphoric acid and DEHP is the corresponding base. Mass transfer studies were performed under conditions of a quiescent constant interface with moderate stirring in one or both phases. The effects of changes in interfacial area, temperature and the stirring rate in each phase on the rate parameters, k1, k2 and k −2 k −1 , and the distribution ratio were determined and are discussed. The salient features of the proposed mechanism are threefold: (1) HDEHP and generally all extractants have important interfacial activity; (2) the actual complexation of calcium ion does not occur in the aqueous phase but at the interface; and (3) there is a structured layer of water at the interface that impedes the progress of calcium ion from the bulk aqueous phase to the interface.

Chemical separations for super-heavy element searches in irradiated uranium targets☆

Abstract A chemical procedure is outlined for super-heavy element searches in irradiated uranium targets. The separation scheme is based on the wide range in stability and extractability of chlorometallic complexes by alkyl tertiary and quaternary ammonium chlorides and the wide range of extractability of metal ions by di-2-ethylhexylorthophosphoric acid. These two properties are utilized in various extraction chromatographic systems. The procedure was developed using elements in the sixth period as chemical homologues of super-heavy elements and tested on 100–200 mg irradiated uranium targets. The separation schemes are also applicable to other irradiated targets.

THE EXTRACTION CHROMATOGRAPHY OF CALIFORNIUM, EINSTEINIUM, AND FERMIUM WITH DI(2-ETHYLHEXYL)ORTHOPHOSPHORIC ACID.

Abstract The extraction chromatography of Cf(III), Es(III), and Fm(III) was studied using di(2-ethylhexyl)orthophosphoric acid (HDEHP) adsorbed on hydrophobic diatomaceous earth. Dilute nitric and hydrochloric acid solutions were used as the elutriants. Column performance was studied as a function of particle size, capacity, flow rate, and temperature by measuring the number of theoretical plates obtained for Cf(III) and Es(III) elutions. The distribution coefficients of Cf(III), Es(III), and Fm(III) and the separation factors, Es/Cf and Fm/Es, were studied as a function of temperature with HDEHP adsorbed on Celite, pure undiluted HDEHP, and HDEHP in heptane. The extraction chromatography method was applied to the separation of Es(III) and Fm(III).

The preparation, performance and factors affecting band spreading of high efficiency extraction chromatographic columns for actinide separations☆

Abstract High efficiency extraction chromatographic columns containing di(2-ethylhexyl)orthophosphoric acid (HDEHP) as the stationary phase and Celite as the inert support were prepared by a slurry packing method. Column performance was studied as a function of particle size of the support, liquid loading of HDEHP, temperature, column cross-sectional area and bed length by measuring the plate height, H , as a function of mobile phase velocity, ν, for the elutions of Cf(III) and Cm(III). In order to determine the major causes of band spreading for the elution of Cf(III), self-diffusion coefficients of Eu(III) were measured in dilute HNO 3 and undiluted HDEHP as a function of temperature. H vs ν data were analyzed in terms of the reduced plate height and velocity. Comparison of calculated and experimental H vs ν and H vs capacity factor, k ′, curves showed that the slow rate of extraction of Cf(III) from the stationary to the mobile phase was the major cause of band spreading at 25°C, whereas, flow phenomena were the major causes of band spreading at 75°C.

The extraction chromatography of americium, curium, berkelium and californium with di(2-ethylhexyl)orthophosphoric acid

Abstract The extraction chromatography of Am(III), Cm(III), Bk(III), and Cf(III) was studied using di(2-ethylhexyl)orthophosphoric acid (HDEHP) adsorbed on hydrophobic diatomaceous earth (Celite-545). Dilute nitric and hydrochloric acid solutions were used as the elutriants. The effect of flow rate on the plate height was measured and compared for Cm(III), Am(III), Bk(III), Cf(III), and Es(III) at 25°C. The distribution coefficientsof Am(III), Cm(III), Bk(III), and Cf(III) and the separation factors Cm(III)/Am(III), Bk(III)/Cm(III), Cf(III)/Bk(III), and Cf(III)/Cm(III), were studied as a function of temperature with HDEHP adsorbed on Celite and HDEHP in heptane. The extraction chromatography method was applied to the separation of Bk(III) and Cf(III) and to the separation of Cm(III) and Cf(III).

The liquid-liquid extraction of certain tripositive transplutonium ions from salted nitrate solutions with a tertiary and quaternary amine

Abstract The distribution coefficients of Am(III), Cm(III) and Cf(III) were measured from Li, Mg, Ca, Al and Fe(III) nitrate solutions using a high molecular weight tertiary and quaternary amine. The distribution coefficient of Am(III) was measured for the tertiary and quaternary amine systems as a function of the diluent, aqueous acid concentration, extractant concentration and aqueous nitrate concentration. Separation factors for Cm(III)/Am(III), Cf(III)/Am(III), Es(III)/Cf(III) and Eu(III)/Am(III) were determined for the two amine systems. The quaternary amine was shown to be a superior extractant for the trans plutonium (III) ions compared to the tertiary amine.

Comparative liquid-liquid extraction behaviour of europium (II) and europium (III)

Abstract The liquid-liquid extraction behaviour of Eu(II) into solutions of acidic phosphoric and phosphonic esters has been investigated both on a macro-scale and tracer-scale. The distribution ratio of Eu(II) was investigated as a function of extractant concentration in the organic phase and HCl concentration in the aqueous phase using β-active 13, 16 year 152, 154 Eu. Advantage was taken of the large separation factors Pm(III)/Eu(II), Sm(III)/Eu(II), and Gd(III)/Eu(II) in effecting the mutual separation of 147 Pm and 152, 154 Eu, the high purification of 147 Pm with respect to 152, 154 Eu, and the enrichment, concentration and recovery in high yield of europium from a rare earth oxide containing 0·1 per cent Eu.

Nuclear decay properties of light einsteinium isotopes

Abstract The light einsteinium isotopes 248 Es, 249 Es, 250 Es and 251 Es were synthesized by irradiating a 249 Bk target with 3 He and 4 He ions. Because of the short half-life of 248 Es, it was necessary to characterize this isotope by using the recoil technique, whereas the other isotopes were chemically purified before their properties were determined. The half-lives of the above nucleides were found to be 28 ± 5 min, 1.7 ± 0.1 h, 8.3 ± 0.2 h and 33 ± 1 h, respectively. A new isomer of 250 Es was discovered and its half-life was determined to be 2.1 ± 0.2 h. The energies of the main α groups for 248 Es, 249 Es and 251 Es were observed to be 6.87 ± 0.01, 6.770 ± 0.005 and 6.488 ± 0.005 MeV, respectively. The α/K X-rays ratio for 249 Es was found to be 0.007 ± 0.001 and the value for 251 Es was 0.008±0.002. Several gamma rays associated with the electron-capture decay of the einsteinium isotopes were observed. On the basis of the present investigation the ground states of 249 Es and 251 Es have been assigned to the Nilsson states 7 2 + (633↑) and 3 2 − (521↑) , respectively.

High speed-high efficiency separation of the transplutonium elements by extraction chromatography☆

Abstract The separation of various tripositive transplutonium elements by high efficiency extraction chromatographic columns using di(2-ethylhexyl)orthophosphoric acid (HDEHP) as the stationary phase was analyzed in terms of the resolution function. Resolution, R s , for Bk(III)-Cf(III) system was studied as a function of column length and particle size of inert support. R s vs v curves at different temperatures were calculated for Cm(III)/Am(III), Cf(III)/Bk(III), Fm(III)/Es(III) and Md(III)/Fm(III). The data was used to select conditions for high speed seperations of Cm and Cf, Bk and Cf, Bk, Es and Fm, and Es, Fm and Md using high efficiency HDEHP columns. Very high resolution HDEHP columns containing over one thousand plates were also studied. The reproducibility and stability of HDEHP-Celite columns were studied as a function of particle size, liquid loading, temperature and flow velocity.