Diamyl Amylphosphonate Research Articles

Organic and Aqueous Redox Speciation of Cu(III) Periodate Oxidized Transuranium Actinides

A hexavalent group actinide separation process could streamline used nuclear fuel recycling and waste management. The limiting factor to such a process compatible with current fuel dissolution practices is obtaining and maintaining hexavalent Am, AmO22+, in molar nitric acid because of the high reduction potential of the Am(VI)/Am(III) couple (1.68 V vs SCE). Two strong oxidants, sodium bismuthate and Cu3+ periodate, have demonstrated quantitative oxidation of Am under molar acid conditions, and better than 50% recovery by diamyl amylphosphonate (DAAP) is possible under these same conditions. This work considers the use of Cu3+ periodate to oxidize Np(V) to Np(VI) and Pu(IV) to Pu(VI) and to recover these elements by extraction with DAAP. A metal:oxidant ratio of 1:1.2 and 1:3 was necessary to quantitatively oxidize Np(V) and Pu(IV), respectively, to the hexavalent state. Extraction of hexavalent Np, Pu, and Am by 1 M DAAP in n-dodecane was measured using ultraviolet–visible (PuO22+, AmO22+) and near-infr...

Hexavalent Actinide Extraction Using N,N-Dialkyl Amides

Recently, efforts toward closing the nuclear fuel cycle have considered oxidizing americium to a hexavalent, linear-dioxo cation for co-recovery with hexavalent U, Np, and Pu from molar nitric acid using solvating extraction ligands such as tributyl phosphate or diamyl amylphosphonate. This work assesses solvent extraction recovery of sodium bismuthate oxidized americium by N,N-di(2-ethylhexyl)butyramide (DEHBA), N,N-di(2-ethylhexyl)isobutyramide (DEHiBA), and N,N-dihexyloctanamide (DHOA). Extraction efficiency between the monoamides was found to increase in the order of DEHiBA < DHOA < DEHBA. For all monoamides, oxidized americium extraction was less than 50% from 4 M HNO3 and below. Extraction efficiency above 50% was obtained using concentrations of 5 M HNO3 or higher. The DEHBA extractant provided the highest distribution value of 5.4 at 7 M HNO3. Distribution values were found to be stable for up to 45 s aqueous/organic phase mixing times and indicated decreased reduction of hexavalent americium rela...

Solubility of dialkylalkyl phosphonates in supercritical carbon dioxide: Experimental and modeling approach

Dialkylalkyl phosphonates have found renewed interest in the selective extraction of actinides from different matrices. In this context, two dialkylalkyl phosphonates, dibutylbutyl phosphonate (DBBP) and diamylamyl phosphonate (DAAP) were synthesised and their solubilities in supercritical carbon dioxide (SCCO2) medium were determined in the pressure range of 10–25 MPa at 313–333 K. Solubility studies were carried out to examine their utility as ligands during supercritical fluid extraction of actinides. Solubilities of dialkylalkyl phosphonates ranged from 0.06 to 0.12 mole fraction. Experimental solubilities were correlated using Mendez-Santiago, Chrastil, solution theory with Wilson activity coefficient model and association model based on van Laar activity coefficient model. Comparison among these models revealed that the association model with van Laar activity coefficient model provides better solubility predictions. SCCO2 containing DAAP was employed for the (i) selective extraction of uranium in the presence of simulated fission products and (ii) extraction of uranyl nitrate from acidic medium.

Hexavalent Americium Recovery Using Copper(III) Periodate

Separation of americium from the lanthanides is considered one of the most difficult separation steps in closing the nuclear fuel cycle. One approach to this separation could involve oxidizing americium to the hexavalent state to form a linear dioxo cation while the lanthanides remain as trivalent ions. This work considers aqueous soluble Cu3+ periodate as an oxidant under molar nitric acid conditions to separate hexavalent Am with diamyl amylphosphonate (DAAP) in n-dodecane. Initial studies assessed the kinetics of Cu3+ periodate autoreduction in acidic media to aid in development of the solvent extraction system. Following characterization of the Cu3+ periodate oxidant, solvent extraction studies optimized the recovery of Am from varied nitric acid media and in the presence of other fission product, or fission product surrogate, species. Short aqueous/organic contact times encouraged successful recovery of Am (distribution values as high as 2) from nitric acid media in the absence of redox active fission products. In the presence of a post-plutonium uranium redox extraction (post-PUREX) simulant aqueous feed, precipitation of tetravalent species (Ce, Ru, Zr) occurred and the distribution values of 241Am were suppressed, suggesting some oxidizing capacity of the Cu3+ periodate is significantly consumed by other redox active metals in the simulant. The manuscript demonstrates Cu3+ periodate as a potentially viable oxidant for Am oxidation and recovery and notes the consumption of oxidizing capacity observed in the presence of the post-PUREX simulant feed will need to be addressed for any approach seeking to oxidize Am for separations relevant to the nuclear fuel cycle.

Sequential separation method for the determination of uranium and thorium in soil using diamyl amylphosphonate and Aliquat®336 impregnated polymer resins

The accurate and rapid determination of radionuclides in soil is very important to monitor the radioactivity of radionuclides for reduction of hazardous effects to human health. Here, a sequential separation method with a fusion technique was developed to separate uranium and thorium isotopes from a soil sample using polymer resins (UTEVA® and TEVA®) packed columns. The radioactivity of separated U and Th was measured using alpha-particle spectrometry. The developed method was evaluated by assessing the key validation parameters of the selectivity, radioactivity range of linearity, scores for quality control, accuracy, tracer recovery yield, and quantification of uncertainty. The method offered a fast analysis of U and Th isotopes of the soil samples with very high chemical recovery yield and the effective removal of interferences, and demonstrated a satisfactory quality level for the selected criteria of the performance for the method validation. The developed method might be promising for use in a determination of the radioactivity of solid samples containing various interferences.

A Molecular Dynamics Study of Tributyl Phosphate and Diamyl Amyl Phosphonate Self-Aggregation in Dodecane and Octane.

A molecular dynamics model for tributyl phosphate (TBP) and diamyl amyl phosphonate (DAAP) is presented using the Generalized AMBER Force Field (GAFF) and the AM1-BCC method for calculated atomic charges with a modification to the phosphorus-containing dihedral parameters. The density and average molecular dipole in a neat liquid simulation, and dimerization in dodecane and octane diluents, compare favorably to experimental values. At low extractant concentration, investigation of the dimer structure reveals the offset "head-to-head" orientation as the predominant structure over a range of TBP and DAAP concentrations with a phosphoryl oxygen separation distance between dimerized extractants of 3-5.5 Å. At high extractant concentrations, a graph analysis of extractant aggregates was used to determine concentrations of each aggregate size and the average coordination number, which gives a measure of the linearity of the aggregates. For aggregates up to 7 extractant molecules, the mean free energy of association per molecule was found to be 0.55-0.59 and 0.72 kcal/mol for TBP and DAAP, respectively. In both diluents, TBP formed large aggregates more frequently than DAAP, and those aggregates were more nonlinear than their DAAP equivalents. This finding anticipates differences in aggregation chemistry between TBP and DAAP in PUREX extraction systems.

Extraction studies of actinides and lanthanides by bifunctional H-phosphonates

Abstract The extraction behavior of actinides and lanthanides was investigated by three homologues of H-phosphonates viz. diamylhydrogen phosphonate (DAHP), dihexylhydrogen phosphonate (DHeHP) and dioctylhydrogen phosphonate (DOHP). These compounds were synthesized, characterized by using elemental analysis, IR, NMR (1H, 13C and 31P) and mass spectroscopy. The extraction behavior of these ligands was compared with a member of dialkylalkyl phosphonate viz. diamylamyl phosphonate (DAAP). The present study has been taken up to understand the influence of phosphorus bonded hydrogen and alkyl groups in H-phosphonates on the extraction behavior of actinides and lanthanides. The important physicochemical properties such as density, viscosity, phase disengagement time, dispersion number and solubility are also reported for the first time. These compounds extract actinides through the P–OH group which is present in tautomeric equilibrium with the P–H bond at lower acidities, and through the phosphoryl group at higher acidities thus exhibiting a dual behaviour. The physical properties can be modified by suitably designing the extractant based on the requirement for a given purpose. The H-phosphonates have potential applications in pre-concentration of large quantities of dilute solutions of uranium and plutonium.

Supercritical fluid extraction of uranium and thorium from nitric acid medium using organophosphorous compounds

Abstract In recent years, Supercritical Fluid Extraction (SFE) technique has been widely used for the extraction of metal ions. In the present study, extraction of uranium from nitric acid medium was investigated using supercritical carbon dioxide (Sc-CO2) containing various organophosphorous compounds such as trialkyl phosphates e.g. tri-iso-amyl phosphate (TiAP), tri-sec-butyl phosphate (TsBP) and tri-n-butyl phosphate (TBP), dialkylalkyl phosphonates, e.g. diamylamyl phosphonate (DAAP) and dibutyl butyl phosphonate (DBBP), dialkyl hydrogen phosphonates, e.g. dioctyl hydrogen phosphonate (DOHP), dioctylphosphineoxide (DOPO), trioctyl phosphine oxide (TOPO), n-octylphenyl N,N-diisobutyl carbamoylmethylphosphine oxide (CMPO) and di-2-ethyl-hexyl phosphoric acid (HDEHP). Some of these ligands have been investigated for the first time in the supercritical phase for the extraction of uranium. The extraction efficiency of uranium was studied with TiAP, DAAP and DBBP as a function of nitric acid concentration; the kinetics of the equilibration period (static extraction) and transportation of the metal complex (dynamic extraction) was investigated. The influence of pressure and temperature on the extraction behaviour of uranium with DAAP was studied from 4 N HNO3. The extraction efficiency of uranium from 4 N nitric acid medium was found to increase in the order of phosphates &lt; phosphonates &lt; HDEHP &lt; TOPO &lt; CMPO. In the case of phosphates and phosphonates, the maximum extraction of uranium was found to be from 4 N HNO3 medium. The acidic extractants, HDEHP and DOHP showed relatively higher extraction at lower acidities. The relative extraction of uranium and thorium from their mixture was also examined using Sc-CO2 containing phosphates, phosphonates and TOPO. The ligand, TsBP provided better fractionation between uranium and thorium compared to trialkyl phosphates, dialkyl alkyl phosphonates and TOPO.

Studies on extraction of actinides by unsymmetrical diamylbutyl phosphonate

Abstract This paper reports the extraction behavior of uranium and thorium by diamylbutyl phosphonate (DABP). This extractant was synthesized, characterized by various techniques like carbon and hydrogen analysis, IR, NMR (1H, 13C and 31P) and mass spectra. This paper reports the physicochemical properties like density and viscosity of this ligand. The tracer and macro extraction of uranium and thorium and stoichiometry of the extracted species of actinides by DABP is presented in this paper. This compound is an unsymmetrical phosphonate and is compared with symmetrical member of the same family, diamylamyl phosphonate (DAAP) and a member of trialkyl phosphate family, viz. tributyl phosphate (TBP).

Characterizing Diamylamylphosphonate (DAAP) as an Americium Ligand for Nuclear Fuel-Cycle Applications

Successful deployment of the currently-envisioned advanced nuclear fuel cycle requires the development of a partitioning scheme to separate Am from the lanthanides. The Am/lanthanide separation is challenging since all the metals are normally trivalent and have similar ionic radii. Oxidation of Am to higher oxidation states is one option to achieve such a separation. Hexavalent Am has now been routinely prepared in our laboratory in strongly acidic solution using sodium bismuthate as the oxidant, and then extracted into diamylamylphosphonate/dodecane solution. Here, we have characterized this phosphonate-containing solvent with regard to the extraction of Am, the lanthanides, Cm, other fission product, and/or inert constituents expected in dissolved nuclear fuel. Additionally, the effects of irradiation on dispersion numbers and the phosphonate concentration were investigated.

Thermal decomposition characteristics of octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide-tri n-butyl phosphate–nitric acid systems

Thermal stability of neat octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (OΦD[IB]CMPO) and TRUEX solvent composition (0.2M OΦD[IB]CMPO-1.2M tri n-butyl phosphate-in n-dodecane) in the presence and absence of nitric acid has been studied in ambient air in a closed vessel, employing an adiabatic calorimeter. Enthalpies and kinetic parameters for the decomposition reaction were derived wherever possible and are reported for the first time. Neat OΦD[IB]CMPO was found to be thermally stable up to 633 K and exhibited an exothermic decomposition later. It decomposed at lower temperatures (376–386 K) depending on the nitric acid concentration. The exothermic rise in temperature and pressure increased exponentially, while activation energies exhibited exponential decrease for the decomposition reactions with increase in nitric acid content. TRUEX solvent was found to be stable up to 661 K in the absence of nitric acid while in the presence of 8 and 4M HNO3, it decomposed between 387 and 413 K. All these samples on decomposition formed incompressible gases and viscous black liquids. The results also indicate that the neat OΦD[IB]CMPO and the TRUEX solvent are thermally more stable than neat tri n-butyl phosphate (TBP), PUREX solvent (1.1M TBP/n-DD), neat diamyl amyl phosphonate (DAAP) and 1.1M DAAP/n-DD, triisoamyl phosphate (TiAP) and 1.1M TiAP/n-DD.

Thermodynamics and kinetics of thermal decomposition of diamylamyl phosphonate-nitric acid systems

Thermal decomposition of neat diamylamyl phosphonate (DAAP), nitric acid-solvates of DAAP and 1.1M DAAP/n-dodecane was studied calorimetrically in heat-wait-search mode for the first time. The neat DAAP decomposed beyond 500K while DAAP·0.7HNO3, DAAP·HNO3 and DAAP·2.1HNO3 decomposed exothermally at 386, 381 and 366K respectively, indicating the role of amount of nitric acid on decomposition. Mixture of DAAP and 8M nitric acid decomposed at a lower temperature than the acid solvates with a larger excursion in temperature and pressure yielding hydrocarbons, CO2, CO, NOx and a reddish liquid or a black solid residue. Enthalpy of decomposition of DAAP·0.7HNO3, DAAP·HNO3 and DAAP·2.1HNO3 were found to be −237.7±4.8, −348.9±3.4 and −1002.1±2.6kJmol−1 and the activation energy and pre-exponential factors were 127.5±1.5, 121.8±0.8 and 105.3±1.2kJmol−1 and 9.0×1013, 1.4×1012 and 2.2×1010 litmol−1s−1, respectively. Heat capacity (Cp) of acid solvates were measured and used for deriving the enthalpy change.

Estimation of uranium isotope in urine samples using extraction chromatography resin

Introduction: Internal exposure monitoring for alpha emitting radionuclides is carried out by bioassay samples analysis. For occupational radiation workers who handle uranium in reprocessing or fuel fabrication facilities, there exist a possibility of internal exposure and urine assay is the preferred method for monitoring such exposure. Materials and Methods: Separation of Uranium is carried out by extraction chromatography using diamyl amyl phosphonate (U/TEVA) resin. This resin contains diamyl amyl phosphonate extractant supported on inert Amberlite XAD-7 (an acrylic ester) resin.The electrodeposited samples are counted using octet alpha spectrometery. Results and Discussion: The analysis time involved from sample loading to stripping is 2 h compared with the 3.5 h involved in conventional ion exchange method. The radiochemical yield was found in the range of 69-91%. Minimum detectable activity for uranium estimation for 3,60,000 s counting time at an average percentage recovery of 82 ΁ 8 works out to 0.21 mBq/d. Conclusion: The technique gives good and consistent radiochemical yield of 82% on repeated use of the chromatographic column when compared with ion exchange technique. Analysis time involved from sample loading to stripping using UTEVA is 2 h compared with the time involved of 3.5 h by the conventional ion exchange method.

Studies on the Extraction of Actinides by Dibutylbutyl Phosphonate

Dibutylbutyl phosphonate (DBBP) was synthesized by the Michaelis Becker reaction, and was characterized by elemental analysis, IR, and 31P NMR. The extraction of U(VI), Th(IV), Pu(IV), Fe(III), and Am(III) by 1.1 M DBBP in n-dodecane as a function of nitric acid concentration was studied, and the results are compared with the extraction behavior of these ions with tributyl phosphate (TBP) and diamylamyl phosphonate (DAAP) in n-dodecane. The physical properties of the extractant such as the density, surface tension, viscosity, aqueous solubility, and phase-disengagement time with 1.1 M DBBP/n-dodecane have been measured and compared with those of 1.1 M TBP/n-dodecane and 1.1 M DAAP/n-dodecane. Studies on the third-phase formation behavior of 1.1 M DBBP/n-dodecane with U(VI) and Th(IV) nitrates in nitric acid medium have been carried out, and the results are compared with the TBP and DAAP systems. Studies were also carried out to study the U-Fe separation by DBBP impregnated on XAD-4 resin.

Studies on the Extraction of Actinides by Diamylamyl Phosphonate

Diamylamyl phosphonate (DAAP) was synthesised by the Michealis Becker reaction, and was characterized by elemental analysis, IR, and 31P NMR. The extraction of U(VI), Th(IV), Pu(IV) and Am(III) by 1.1 M DAAP in n‐dodecane as a function of nitric acid concentration was studied and the results are compared with the extraction behavior of these ions by tributyl phosphate (TBP) and triamyl phosphate (TAP) in n‐dodecane. Some important physical properties of the extractant that have to be met for its use in industrial scale liquid‐liquid extraction such as density, surface tension, viscosity and phase disengagement time with 1.1 M DAAP/n‐dodecane have been measured and compared with those of 1.1 M TBP/n‐dodecane. Studies on the third phase formation behavior of DAAP/n‐dodecane with U(VI) and Th(IV) nitrates in nitric acid medium have been carried out and the results are reported. The breakthrough and elution behavior of U(VI) using a column packed with 50% (w/w) DAAP impregnated on Amberlite XAD‐7 was studied and reported.

EXTRACTION OF ALKALINE EARTH AND ACTINIDE CATIONS BY MIXTURES OF DI(2-ETHYLHEXYL) ALKYLENEDIPHOSPHONIC ACIDS AND NEUTRAL SYNERGISTS

ABSTRACT The synergistic extraction of alkaline earth (Ca2+, Sr2+, Ba2+ and Ra2+) and actinide (Am3+, UO2 2+ and Th4+) cations from aqueous nitric acid solutions by mixtures of P,P′-di(2-ethylhexyl) methylene-(H2DEH[MDP]), ethylene-(H2DEH[EDP]), and butylene-(H2DEH[BuDP]) diphosphonic acids and neutral extractants in o-xylene has been investigated. The cis-syn-cis and cis-anti-cis stereoisomers of dicyclohexano-18-crown-6 (DCH18C6), the unsubstituted 21-crown-7 (21C7) and dicyclohexano-21-crown-7 (DCH21C7) were used as neutral synergists of the crown ether type. For Am(III) synergistic effects were also investigated using neutral organophosphorus esters, such as, tri-n-butylphosphate (TBP), diamyl amylphosphonate (DA[AP]) and tri-n-octylphosphine oxide (TOPO) as co-extractants. In all systems investigated, no synergistic extraction enhancement was observed for actinide ions. For the alkaline earth cations, synergistic effects were only observed when mixtures of H2DEH[EDP] or H2DEH-[BuDP] with DCH18C6 were used to extract Sr2+, Ba2+ and Ra2+. No synergistic effects were observed for the extraction of alkaline earth cations by H2DEH[MDP] or for the extraction of Ca2+ by any of the diphosphonic acids studied. The synergistic effects obtained with DCH18C6 were significantly higher for the cis-syn-cis than for the cis-anti-cis stereoisomer.

An improved extraction chromatographic resin for the separation of uranium from acidic nitrate media

The preparation and characterization of a new extraction chromatographic resin exhibiting extraordinarily strong retention of hexavalent uranyl ion over a wide range of nitric acid concentrations and very high selectivity for U(VI) over Fe(III) and numerous other cations is described. This new material (designated U/TEVA-2) comprises a novel liquid stationary phase consisting of an equimolar mixture of diamyl amylphosphonate (DA[AP]) and Cyanex 923 ® (a commercially available trialkyl-phosphine oxide, TRPO) sorbed on silanized silica or Amberchrom CG-71. Cyanex 923 is shown to be preferable to a related TRPO, Cyanex 925 ®, due to its lower viscosity and higher selectivity for U(VI) over Fe(III). The retention of uranyl nitrate by the U/TEVA-2 resin, as measured by the k′ values (number of free column values to peak maximum) is >5000 from approximately 0.1 to 8 M HNO 3. The ability of the new resin to strongly and selectively retain U(VI) from such a wide range of acid concentrations, along with its favorable physical properties, make it a good candidate for application in the separation and preconcentration of U(VI) from complex environmental, biological, and nuclear waste samples for subsequent determination.

Cleanup of Hydrochloric ACID Waste Streams from Actinide Processes Using Extraction Chromatography

Abstract Extraction chromatography is under development as a method to lower actinide activity levels in hydrochloric acid (HCl) effluent steams. Successful application of this technique would allow recycle of the largest portion of HCl, while lowering the quantity and improving the form of solid waste generated. The extraction of plutonium and americium from HCl solutions was examined for several commercial and similar laboratory-produced resins coated with n-octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) and either tributyl phosphate (TBP), or diamyl amylphosphonate (DAAP). Distribution coefficients for Pu and Am were measured by contact studies in 1–10 M HCl, while varying REDOX conditions, actinide loading levels, and contact time intervals. Significant differences in the actinide distribution coefficients, and in the kinetics of actinide removal were observed as a function of resin formulation.

Separation and preconcentration of uranium from acidic media by extraction chromatography

A novel extraction chromatographic resin comprised of diamyl amylphosphonate sorbed on an inert polymeric support (Amberlite XAD-7) for the separation and preconcentration of uranium from nitric and hydrochloric acid solutions is described. Uranium sorption by the resin is shown to be most efficient at high (> 1 M) acid concentrations. Sorbed uranium can be readily eluted using dilute acid. The application of the material to the isolation of uranium from various environmental samples (e.g., groundwater and soil) is described. Uranium recoveries from these samples are shown to be consistently high (ca. 95%).

Small-angle neutron scattering studies of the aggregation of Pr(NO3)3–CMPO and PrCl3–CMPO complexes in organic solvents

Small-angle neutron scattering studies have been carried out on praseodymium–CMPO [octyl(phenyl)(N,N-diisobutylcarbamoylmethyl)phosphine oxide] complexes in organic solvents to understand the solution structures of the complexes formed in the TRUEX (transuranic extraction) process. In this investigation, the effects of the concentration of the extractant, the nature of the solvent, the nature of the anions and the bifunctional character of CMPO on the aggregation properties of the extracted species were considered. The results reveal that the PrX3–CMPO (X = NO3, Cl) complexes in C6D6 form large aggregates which have an ellipsoidal shape, although CMPO in C6D6 is a monomer. The size of the aggregates depends upon the concentration of the CMPO. The anion accompanying the praseodymium into the organic phase and coextracted water or acid have little influence on the morphology of the aggregates. The nature of the diluent and the concentration of CMPO, however, strongly influence the size of the aggregates formed. Unlike CMPO, the monofunctional phosphoryl extractant DAAP (diamyl amylphosphonate) does not form large aggregates, suggesting that the aggregation may be associated with the bifunctional nature of the CMPO.