E. P. Horwitz

The Truex Process and the Management of Liquid Tru Uwaste

Abstract The TRUEX (TRansUranium Extraction) process is a new generic actinide extraction/recovery process for the removal of all actinides from acidic nitrate and chloride nuclear waste solutions. A brief review of the relevant chemistry of the TRUEX process and a summary of the current status of development and deployment of TRUEX process flowsheets to treat specific acidic waste solutions at several U.S. DOE sites is presented.

Diphonix® Resin: A Review of Its Properties and Applications

Abstract The recently developed Diphonix® resin is a new multifunctional chelating ion exchange resin containing geminally substituted diphosphonic acid ligands chemically bonded to a styrene-based polymeric matrix. Diphonix can be regarded as a dual mechanism polymer, with a sulfonic acid cation exchange group allowing for rapid access, mostly non-specific, of ions into the polymeric network, and the diphosphonic acid group responsible for specificity (recognition) for a number of metal cations. The Diphonix resin exhibits an extraordinarily strong affinity for actinides, especially in the tetra- and hexavalent oxidation states. Therefore the resin has potential for applications in TRU and mixed waste treatment and characterization, and in the development of new procedures for rapid actinide preconcentration and separation from environmental samples. Metal uptake studies have been extended to alkaline earth cations, to transition and post-transition metal species, and to metal sorption from neutral or ne...

EXTRACTION OF STOONTIUM FROM NITRIC ACID SOLUTIONS USING DICYCLOHEXANO-18-CROWN-5 AND ITS DERIVATIVES

ABSTRACT Dicyclohexano-18-Crown-6 (DCH18C6)and its dimethyl and di-t-butyl derivatives have been evaluated as extractants for Sr (II) from nitric acid media. As with DCH18C6, a correlation is observed between the extraction of strontium nitrate by the di-t-butyl compound dissolved in a variety of oxygenated, aliphatic solvents and the concentration of water in the organic phase. Comparison of the extractant dependencies of the three compounds using n-octanol as the diluent shows that the expected first power dependence of the strontium distribution ratio (Dsr) on crown concentration is observed only for the di-t-butyl derivative. DCH18C6 shows a marked deviation from first power dependence at crown concentrations greater -0.01 M. Dsr acid dependencies for DCHl8C6 and the di-t-butyl derivative do not exhibit the decrease in strontium distribution ratios at high acidities observed for DCH18C6 in chlorinated hydrocarbons.

UPTAKE OF METAL IONS BY A NEW CHELATING ION-EXCHANGE RESIN. PART 1: ACID DEPENDENCIES OF ACTINIDE IONS*

ABSTRACT The uptake of several actinide ions [U(VI), Pu(IV), Np(IV), Th(IV] and Am(DI)) from nitric and hydrochloric acid solutions, and of U(VI) from near-neutral solutions by the new chelating ion-exchange resin, DiphonixTM, has been investigated. Diphonix is a polyfunctional resin containing sulfonic and gem-diphosphonic acid groups chemically bonded in a styrene-divinylbenzene polymeric network. Comparison of the acid dependencies of the actinide ions uptake measured with Diphonix with those obtained using a commercial sulfonic -type resin and a resin containing both sulfonic and monophosphonic aCid groups, hat Shown that Diphonix binds the actinides via a different kind of chemical interaction, involving the.formation of chelate complexes through the phosphoryl groups of the gem-diphosphonic acids. As a consequence, Diphonix is superior to other resins in extracting actinide ions from very acidic solutions. A better performance of Diphonix is also observed with the uptake of uranium from neutral solu...

UPTAKE OF METAL IONS BY A NEW CHELATING ION-EXCHANGE RESIN. PART 4 : KINETICS

Abstract The rate of uptake of several actinide ions [Am(III), U(VI), Th(IV), Np(IV) and Pu(IV)] and of some transition-metal ions [Co(II), Zn(II), Fe(III) and Cr(III)] at tracer concentration level, from solutions of various compositions, by the new chelating ion-exchange resin, DiphonixTm, has been investigated. Diphonix is a polyfunctional resin containing sulfonic and gem-diphosphonic acid groups chemically bonded in a styrene-divinylbenzene polymeric network. It binds actinide and other ions through the formation of chelate complexes with the phosphoryl groups of the gem-diphosphonic acids. The experiments discussed in this work have allowed us to establish the paramount importance of the presence of the sulfonic groups in obtaining practically useful rates of metal ions uptake. Comparison of the kinetic behavior of Diphonix with that of commercial sulfonic-type resins has shown that Diphonix reacts with the investigated ions as rapidly as do the other resins. Conditions for efficient and rapid strip...

CORRELATION OF THE EXTRACTION OF STRONTIUM NITRATE BY A CROWN ETHER WITH THE WATER CONTENT OF THE ORGANIC PHASE

Abstract A simple correlation has been observed between the extraction of strontium nitrate from nitric acid solution by cis-dicyclohexano-18-Crown-6 dissolved in a variety of oxygenated, aliphatic diluents and the molarity of water present in the organic phase. This correlation is attributed to the extraction of the hydrated nitrate ion and its solvation by the diluent, facilitated by the high concentration of dissolved water. Of the solvents studied, ketones yield the largest values of the extraction constant for a given water content, although C5 and C6 alcohols give the highest overall values.

SEPARATION OF ACTINIDES AND LANTHANIDES FROM ACIDIC NUCLEAR WASTES BY SUPPORTED LIQUID MEMBRANES

ABSTRACT Supported liquid membranes, SLM, consisting of a solution of 0.25 M octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) and 0.75 μ tributylphosphate (TBP) in decalin absorbed on thin micropocous polypropylene supports, have been studied for their ability to perform selective separations and concentrations of actinide and lanthanide ions from synthetic acidic nuclear wastes. The permeability coefficients of selected actinides (Am, Pu, U, Np) and of some of the other major components of the wastes have been measured using SLMs in flat-sheet and hollow- fiber configurations. The results have shown that with the thin (25 μm) flat-sheet SLMs, using Celgard® 2500 as support, the membrane permeation process is mainly controlled by the rate of diffusion through the aqueous boundary layers. With the thicker (430 μmpar; hollow-fiber SLMs, using Accurel® hollow-fibers as support, the membrane permeation process Is controlled by the rate of diffusion through both the SLM and the aqueous boundar...

ACID DEPENDENCY OF THE EXTRACTION OF SELECTED METAL IONS BY A STRONTIUM.SELECTIVE EXTRACTlON CHROMATOGRAPHIC RESIN: CALCULATEDVS.EXPERIMENTAL CURVES*

ABSTRACT The extraction of selected divalent (Ca+2, Sr+2, Ba+2, Ra+2, Pb+2, UO2 +2) and monovalent (Na+, K+, Rb+, CS+, TI+) metal cations at tracer concentration level by a recently introduced strontium-selective extraction chromatographic resin has been studied as function of the nitric acid concentration in the range − 0.1-7 M. The data have been explained by combining the metal extraction, the acid extraction, and the aqueous phase metal complication equilibria. Conditional metal extraction equilibrium constants have been estimated by using calculated activity coefficients of the metal nitrate salts in the nitric acid solutions. The extraction constants have been used to predict the effect of macroconcentrations of sample matrix constituents on the extraction of Sr+2 or Pb+2 by the strontium-selective resin.

The application of novel extraction chromatographic materials to the characterization of radioactive waste solutions

A simple method for the separation and preconcentration of radiostrontium from acidic nuclear waste solutions for subsequent determination is described. The method involves passage of the waste solution, acidified to at least 2M with nitric acid, through an extraction chromatographic column consisting of a 1M solution of bis-4,4′(5′)[(t-butyl)cyclohexano]-18-crown-6 in 1-octanol sorbed on an inert polymeric substrate, which preferentially retains strontium. The strontium may then be stripped from the column with a small volume of either dilute (≤0.05M) nitric acid or water. Actinides present are removed quantitatively prior to strontium separation by passage of the sample through an actinide-specific extraction chromatographic column.

Hydrolytic and Radiolytic Degradation of Oφd(iB)Cmpo: Continuing Studies

Abstract The hydrolytic and radiolytic degradation of octyl(phenyl)-N, N-diisobutylcarbamoyl-methylphosphine oxide (CMPO) in tetrachloro-ethylene (TCE) and in tributylphosphate-TCE mixtures (TRUEX process solvent) in contact with HNO3 has been investigated. Gas chroma-tographic analysis of the degraded solutions has allowed identification and quantitation of a variety of organophosphorus degradation compounds derived from CMPO. The effect of degradation of the extractant solutions on the extraction and stripping of americium has been addressed, as has the effectiveness of Na2CO3 scrub procedures for restoring extractant performance. Extrapolation of these results to normal process application conditions indicates that neither hydrolysis nor radiolysis should compromise the americium extraction performance of TRUEX-TCE.