E. Philip Horwitz

Separation and preconcentration of actinides by extraction chromatography using a supported liquid anion exchanger : application to the characterization of high-level nuclear waste solutions

A novel extraction chromatographic resin comprised of a quaternary amine-based liquid anion exchanger sorbed on an inert polymeric substrate for the sorption of actinides from nitric and hydrochloric acids is described. The resin is shown to exhibit preferential retention of tetravalent actinides over a wide range of acidities. The application of this material to the separation and preconcentration of selected actinides from high level nuclear waste solutions for subsequent determination is described.

Concentration and separation of actinides from urine using a supported bifunctional organophosphorus extractant

Abstract A method has been developed to isolate quantitatively the actinide elements (as a group) from urine samples and to produce near massless electrodeposits suitable for high-resolution α-spectrometry. The actinides are concentrated from the bulk urine sample by coprecipitation with calcium phosphate. The precipitate is then ashed, dissolved in dilute nitric acid and passed through a column of octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) dissolved in tributyl phosphate (TBP) supported on an inert substrate (Amberlite XAD-7) which absorbs the actinides. The actinides are stripped from the column with dilute ammonium hydrogenoxalate, electrodeposited on a stainless-steel disk and counted on an α-spectrometer. Recoveries of added tracers are uniformly high (⩾ 90%) so that samples can be routinely run without yield monitors, permitting an α peak anywhere in the spectrum to be detected with few interferences. Detection limits are influenced only by the available sample size, counting time and counter backgrounds.

THE EXTRACTION OF Am(III) FROM NITRIC ACID BY OCTYL(PHENYL)-N,N-DIISOBUTYLCARBAMOYLMETHYLPHOSPHINE OXIDE - TRI-n-BUTYL PHOSPHATE MIXTURES

Abstract The extraction behavior of Am(III) from nitric acid by octy1(phenyl)-N,N-diisobutylcarbamoyl methyphosphine oxides, OOD[IB]CMPO, in the presence of tributylphosphate, TBP, has been studied using diethylbenzene, decalin, and normal aliphatic hydrocarbon diluents. Relative to OD[IB]CMPO alone, mixtures of TBP and OOD[IB]CMPO show a slight enhancement in the extraction of Am(III) from nitric acid solution above 2 M and a moderate decrease in extraction for lower acid concentrations. The net effect of TBP addition to OOD[IB]CMPO (as well as other selected carbamoyl methylphosphoryl extractants) is a relative insensitivity of the distribution ratio of Am(III) to HNO3 concentration in the range of 0.5 M to 6 M and facilitated stripping of Am(III) with dilute acid. Since a continuous variation study of Am(III) extraction using mixtures of OOD[IB]CMPO and TBP at a fixed total concentration revealed no evidence of a mixed complex, the TBP appears to be behaving primarily as a phase modifier The most signi...

Separation of coal macerals

Abstract The conditions necessary for efficient, small-scale separation of coal macerals are investigated. The method developed takes advantage of known density differences of the various macerais, but unlike most separations, an isopycnic density gradient centrifugation (DGC) technique is used to isolate pure macerals. The technique consists of grinding the coal in a fluid energy mill to ≈ 3 μm average particle size, separating macerals in an aqueous CsCI density gradient, and analysing the products for maceral composition as a function of density. Excellent separations can be achieved in a single run if the coal is first demineralized and then well dispersed with a wetting agent. Sink-float separations also benefit substantially from the addition of a surfactant. The density gradient centrifugation technique is limited more by inability to liberate macerals from each other on comminution than by any inherent errors in the gradient technique itself. Resolution of pure macerals using the DGC technique is much better than would be obtained from sink-float techniques. Data for three coals of differing constitution are presented.

DIPEX: A new extraction chromatographic material for the separation and preconcentration of actinides from aqueous solution

A novel extraction chromatographic resin consisting of a liquid diphosphonic acid supported on an inert polymeric substrate for the sorption of actinides from strongly acidic chloride media is described. The resin is shown to exhibit stronger affinity for actinides in the tri-, tetra- and hexavalent oxidation states and superior selectivity for americium(III) over aluminum(III) or iron(III) than an analogous chelating ion-exchange resin containing chemically bonded geminally substituted diphosphonic acid functionalities. These properties, along with the comparative ease of recovery of sorbed actinides, make the resin readily applicable to the separation and preconcentration of actinides, as a group, from complex matrices such as soils and bioassay samples.

A lead-selective extraction chromatographic resin and its application to the isolation of lead from geological samples

Abstract A novel extraction chromatographic resin comprised of a 0.75 M solution of the macrocyclic polyether bis-4,4′(5′)-[tert.-butylcyclohexano]-18-crown-6 in isodecanol supported on an inert, polymeric substrate for the separation and preconcentration of lead from acidic media is described. The material is shown to retain lead efficiently and selectively over a wide range of nitric acid concentrations. Sorbed lead is readily recovered using any of a variety of complexing agents. The resin is demonstrated to be sufficiently stable to handle large sample volumes or to permit reuse. Application of the resin to the isolation of lead from geological samples for subsequent mass spectrometric determination of isotopic ratios is described.

The Synthesis and Purification of the Carbamoylmethylphosphine Oxides

ABSTRACT The details of the synthesis and purification of symmetrical and unsymmetrlcal carbamoylmethylphosphine oxides (CMPO s) are described. The approaches used to provide a variety of substitution patterns around the two potential donor groups include the Arbusov, Michaelis-Becker and Grignard reactions. Several methods for purifying the extractants were studied. The use of acidic and basic ion exchange resins in conjunction was developed for the removal of acidic impurities which are very troublesome to the extraction performance of these compounds.

Extraction Chromatography Versus Solvent Extraction: How Similar are They?

Abstract Over the last decade, extraction chromatography (EXC) has emerged as a versatile and effective method for the separation and preconcentration of a number of metal ions. Frequently, EXC is described as a technique that combines the selectivity of solvent extraction (SX) with the ease of operation of chromatographic methods. Despite this, the extent to which EXC actually provides the selectivity of SX and to which solvent extraction data can be used for the quantitative prediction of the retention of metal ions on an EXC column has remained unclear. To address these questions, the extraction chromatographic and solvent extraction behavior of lanthanides using three different acidic organophosphorus extractants bis‐(2‐ethylhexyl) phosphoric acid (HDEHP), 2‐ethylhexyl 2‐ethylhexylphosphonic acid (HEH[EHP]), and bis‐(2,4,4 trimethylpentyl)phosphinic acid (H[DTMPeP])) have been compared. Specifically, the rate and extent of uptake of selected lanthanides by the three extractants have been examined. In addition, the relationship between the volume distribution ratios obtained in the chromatographic and liquid–liquid extraction modes have been compared and their utility in predicting the chromatographic parameter, k′, the number of free column volumes to peak maximum determined.

Extraction of strontium from acidic nitrate media using a modified PUREX solvent

ABSTRACT A new process for the extraction and recovery of strontium from acidic waste streams is described. In this process, a modification of the previously described SREX (for strontium extraction) process, strontium is extracted from acidic (≥ 2 M nitric acid) solution using a 0.2 M solution of di-t-butylcyclohexano-18-crown-6 in any of a variety of phase modifier / paraffinic hydrocarbon mixtures, among them a PUREX-like diluent comprised of a 1.2 M solution of tri-n-butyl-phosphate in Isopar L. Tests of this process solvent on a synthetic dissolved sludge waste show that only strontium and barium are appreciably extracted by the crown ether under the experimental conditions. As expected, uranium and plutonium are extracted even in the absence of the crown ether.

THE EXTRACTION OF SELECTED ACTINIDES IN THE ( III) (IV) AND ( VI) OXIDATION STATES FROM HYDROCHLORIC ACID BY Oπ D( iB) CMPO: THE TRUEX-CHLORIDE PROCESS∗

ABSTRACT The extraction of tetravalent Th, Np, and Pu and hexavalent U from hydrochloric acid was studied using octyl(phenyl)-N,N-diiso-butylcarbamoylmethylphosphine oxides, 0π D(iB)CMP0 or CMPO, dissolved in tetrachloroethylene (TCE). A 0·5 MCMPO solution in TCE was found to be an extremely effective extractant for the tetravalent actinides and U(VI) from moderate to concentrated HC1. Extractant dependencies of the distribution ratios of Th(IV), U(VI), and Pu(IV) were 3rd, 2nd, and 3rd power, respectively, indicating the following species: ThCl4’3CMPO, UO2Cl22CMP0, and PuCl4»3CMPO. The distribution ratios of a variety of non-actinide elements, including selected alkali, alkaline earths, Al, transition and post-transition metal ions were also measured from 2 Mand 6 M_ HC1. Based on the distribution ratios of tri-, tetra-, and hexavalent actinides from chloride media, a generic actinide extraction/recovery process was developed for the removal of actinides from chloride salt wastes. The process is called T...