Uranium and Plutonium Extraction from Nitric Acid by N,N-Di(2-Ethylhexyl)-2,2-Dimethylpropanamide (DEHDMPA) and N,N-Di(2-Ethylhexyl)Butanamide (DEHBA) using Mixer-Settler Extractors

Extraction properties of N,N-di(2-ethylhexyl)-2,2-dimethylpropanamide (DEHDMPA) for nitric acid, U(VI), and Pu(IV) were studied by a batch method using various nitric acid concentrations. The distribution ratio equations for nitric acid, U(VI), and Pu(IV) were derived. A continuous counter-current experiment was performed using mixer-settler extractors to determine the performance of a process that uses two types of monoamides, DEHDMPA and N,N-di(2-ethylhexyl)butanamide (DEHBA), as extractants. This process consisted of two cycles: one dedicated to extraction of U(VI) by DEHDMPA, and the other dedicated to the co-extraction of U(VI) and Pu(IV) by DEHBA. The feed solution used for the continuous counter-current experiment was 4 mol/dm³ nitric acid containing U(VI), Pu(IV), and simulated fission products. DEHDMPA exclusively extracted U(VI) from the feed at the 1st cycle, and the ratio of U recovered in the U fraction stream was 99.93%. The residual U and almost all Pu were extracted by DEHBA in the 2nd cycle, and the recovery of Pu in the U-Pu fraction stream was 99.94%. Concentration profiles of U and Pu in mixer-settlers were calculated using a simulation code, which confirmed that the calculation was effective for estimating the U concentration in the U fraction stream, and the U and Pu concentrations in the U-Pu fraction stream.     

Distribution Behavior of Neptunium by Extraction with N,N-dialkylamides (DEHDMPA and DEHBA) in Mixer-Settler Extractors

The extraction properties of N,N-di(2-ethylhexyl)-2,2-dimethylpropanamide (DEHDMPA) and N,N-di(2-ethylhexyl)butanamide (DEHBA) for Np(V) and Np(VI) were studied by a batch method using various nitrate ion concentrations. The distribution ratios of Np(VI) obtained with DEHDMPA and DEHBA exceeded unity when the nitrate ion concentration was > 3 mol/dm³, while DEHDMPA and DEHBA barely extracted Np(V). A continuous counter-current experiment using mixer-settler extractors was performed to evaluate the behavior of Np in a process comprising two cycles using DEHDMPA and DEHBA as extractants. The feed was nitric acid containing U, Pu, Np, and several fission products. The results indicated that part of Np(V) changed its valence state to Np(IV) or Np(VI) after the 1st experimental cycle. The recoveries of Np in the streams of U fraction and U-Pu fraction were 63.7% and 29.1%, respectively.     

Extraction of Trivalent Rare Earths and Minor Actinides from Nitric Acid with N,N,N’,N’-Tetradodecyldiglycolamide (TDdDGA) by Using Mixer-Settler Extractors in a Hot Cell

Single-stage batch experiments to reveal the extraction properties of N,N,N’,N’-tetradodecyldiglycolamide (TDdDGA) for Y, La, Eu, Nd, and Am in nitric acid were carried out. The distribution ratios of Y, Eu, Nd, and Am exceeded 10 when the nitric acid concentration was 1–2 mol/dm³ (M), and the distribution ratio of La was 5.5 when the nitric acid concentration was 2 M. A continuous counter-current experiment using 0.1 M TDdDGA diluted with n-dodecane was performed using mixer-settler extractors installed in a hot cell. Nitric acid with a concentration of 2.1 M containing minor actinides (MAs: Am and Cm), rare earths (REs: Y, La, Nd, and Eu), and other fission products (Sr, Cs, Zr, Mo, Ru, Rh, and Pd) was fed to the extractor. TDdDGA effectively extracted MAs and REs from the feed, while other fission products were barely extracted. The extracted MAs and REs were back-extracted by bringing them in contact with 0.02 M nitric acid, and they were collected as the MA–RE fraction. The results indicated that more than 98% of Am and Cm in the feed were recovered in the MA–RE fraction. The proportions of Y, La, Nd, and Eu in the MA–RE fraction were 94.0%, 99.9%, 99.9%, and 86.9%, respectively.     

Evaluation of two-phase separation in N,N-di(2-ethylhexyl)butanamide-nitric acid systems using turbidity measurements

Quantitative evaluation of the two-phase separation between N,N-di(2-ethylhexyl)butanamide (DEHBA) and tri-n-butyl phosphate (TBP) diluted with n-dodecane and uranyl nitrate solution in nitric acid medium was achieved using turbidity measurements. The turbidities of DEHBA were relatively high, particularly at high DEHBA concentrations, while that of TBP rapidly decreased irrespective of nitric acid concentration. A high concentration of DEHBA, nitric acid, and uranium increased the turbidities in the organic phase, which could be ascribed to the increase in viscosity. Distribution ratios of uranium were also measured, and it was indicated that turbidity did not have a critical effect on the distribution ratio when the turbidity was below a certain value.     

Minor Actinides Separation by N,N,N’,N’,N’’,N’’-Hexaoctyl Nitrilotriacetamide (HONTA) Using Mixer-settler Extractors in a Hot Cell

ABSTRACT

A continuous counter-current test to separate minor actinides (MAs: Am and Cm) by N,N,N’,N’,N’’,N’’-hexaoctyl nitrilotriacetamide (HONTA) as an extractant was performed using mixer-settler extractors installed in a hot cell. Nitric acid of 0.08 M (mol/dm³) containing MAs and rare earths (REs) recovered from high-level liquid waste was used as the feed, and the experiment was conducted for 14 h. MAs were extracted by 0.05 M HONTA dissolved in n-dodecane, with Am and Cm being recovered at 94.9% and 78.9%, respectively. HONTA hardly extracted Y, La, and Eu from the feed (99.9% for Y, 99.9% for La, and 96.7% for Eu), most of which were distributed to the RE fraction. A portion of Nd was extracted by HONTA, and consequently the ratio of Nd in the RE fraction was 83.5%. HONTA could separate MAs and REs by adjusting the nitric acid concentration without using complexants. In addition, the concentrations of MAs and some REs in each stage were calculated using a simulation code, and the results are consistent with the experimental values. This code indicates that the ratios of MAs in the MA fraction and REs in the RE fraction could be ≥99% by optimizing separation conditions.     

Separation of U(VI) and Pu(IV) from Am(III) and Trivalent Lanthanides with Tri-iso-amyl Phosphate (TiAP) as the Extractant by Using an Ejector Mixer-Settler

Counter-current solvent extraction runs have been carried out to develop a suitable flow sheet for fast reactor fuel reprocessing with 1.1M Tri-iso-amyl Phosphate (TiAP)/Heavy Normal Paraffin (HNP) as the solvent by using an ejector mixer-settler facility. A spent solvent of 1.1M TiAP/HNP used for earlier runs has been employed in the present study after the regeneration. Separation of U(VI) and Pu(IV) from Am(III) and lanthanides such as La(III), Pr(III), Nd(III), Sm(III), and Eu(III) as fission product representatives with the above solvent has been investigated with an optimized flow sheet. Stage profile data generated for the extraction and strip runs for the above separation have been reported. Overall and stage-wise mass balance data for the above runs are also discussed.     

N,N-二(2-羟乙基)己二酰胺新型固化剂的合成及表征

以己二酸和甲醇为原料,在对甲苯磺酸催化下合成己二酸二甲酯。再以合成的己二酸二甲酯为原料,在钛酸正丁酯的催化下,与乙醇胺反应,合成了一种新型固化剂—N,N-二(2-羟乙基)己二酰胺。通过FT-IR,1H-NMR对N,N-二(2-羟乙基)己二酰胺的结构进行了表征。实验探讨了酰胺化反应中,催化剂用量、反应温度和反应时间对产物产率的影响,反应条件温和,易于操作,产率可达到95%。     

Thermodynamic and Spectroscopic Studies on Am(III) and Eu(III) in the Extraction System of N,N,N',N'-Tetraoctyl-3-Oxapentane-1,5-Diamide in n-Dodecane/Nitric Acid

Abstract

Thermodynamic parameters (ΔG, ΔH, and ΔS) for the extraction of trivalent f-elements, M(III) (M = Am, Eu), with N,N,N',N'-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) were determined in nitric acid/n-dodecane extraction system. The extraction of M(III) with TODGA was more exothermic than those with octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide (CMPO) and dihexyl-N,N-diethylcarbamoylmethyl phosphonate (DHDECMP). The difference in ΔH between the extractants was attributed to the difference in the binding mode between them, i.e. tridentate (TODGA) and bidentate (CMPO and DHDECMP). In addition, from the results of luminescence lifetime measurement, it was found that the inner-sphere of extracted Eu(III) was dehydrated completely, and occupied by TODGA and/or NO₃ ^?.     

Solvent extraction of metal ions using a new extractant,biuret(C8)

A new extractant biuret(C8) is synthesized and tested for solvent extraction of hard acid metals, for example, actinides, and soft acid metals. This compound has a central frame similar to that of malonamide but with an additional amino functional group introduced into the central framework; in this case, both the amidic oxygen atoms and the amino nitrogen atom may bond with metals. We found that both hard and soft acid metals can be extracted from nitric or perchloric acids to n-dodecane using biuret(C8). It is clear that D(Pd, Pu, U) values of approximately 100 can be obtained using 0.1 M biuret(C8)/n-dodecane.     

Extraction Equilibria of 4-Hydroxypyridine using Di (2-ethylhexyl) Phosphoric Acid

Extractions of 4-Hydroxpyridine (4HP) from aqueous solutions using Di(2-ethylhexyl)phosphoric acid (D2EHPA) as extractant in 1-octanol and kerosene were studied. The factors that affected the distribution coefficient (D), such as equilibrium pH, the concentration of D2EHPA, and the type of diluents were discussed. The interaction mechanism between 4HP and D2EHPA was validated by infrared spectroscopic analysis. D increased with the increase of the concentration of D2EHPA and peak values appeared at equilibrium pH = 3.6–5.0. D in the polar diluent (1-octanol) was much higher than those in the non-polar diluent (kerosene). The extraction reaction was found to be a proton-transfer process and D2EHPA mainly reacted through its –OH with –N– of 4HP. The apparent reactive extraction equilibrium constants K ₁₁ and K ₁₂ were obtained by fitting the experimental data of extraction equilibrium. By comparing calculated D values from the proposed model with the experimental ones, the accuracy of the proposed model was examined.     

Studies on the Separation and Recovery of Thorium from Nitric Acid Medium using (2-ethyl hexyl) Phosphonic Acid,Mono (2-ethyl hexyl) Ester (PC88A)/N-Dodecane as Extractant System

This paper deals with the studies on the separation and recovery of thorium and 233-uranium from nitric acid medium using (2-ethyl hexyl) phosphonic acid, mono (2-ethyl hexyl) ester/n-dodecane as an extractant system. The different extraction parameters were investigated. The distribution ratio of thorium decreased with increase in nitric acid concentration. The optimum solvent concentration for quantitative separation of thorium from aqueous feed solution was 0.75 M of PC88A whereas dodecane was the most suitable of diluents with an organic to aqueous phase ratio of 1:1. Among the various strippants used, 2 M solution of (NH₄)₂CO₃ was found to be the most suitable for back extraction of thorium. The developed method was used to recover thorium and ²³³U from radioanalytical waste generated during thorium analysis by ethylene diamine tetraacetic acid (EDTA) titremtric method and recoveries for both Th and U were more than 85%.     

Synergistic Extraction of U(VI), Th(IV), and Lanthanides(III) from Nitric Acid Solutions Using Mixtures of TODGA and Dinonylnaphthalene Sulfonic Acid

The extraction of U(VI), Th(IV), and lanthanides(III) from aqueous nitric acid solutions with mixtures of N,N,N′,N′-tetra(n-octyl)diglycolamide (TODGA) and dinonylnaphtalene sulfonic acid (HDNNS) in n-decane has been investigated. The extraction efficiency of U(VI), Th(IV), and Ln(III) ions is greatly enhanced by addition of HDNNS to an organic phase containing TODGA. The synergistic effect arises from the higher hydrophobicity of U(VI), Th(IV), and Ln(III) extracted species formed by TODGA and DNNS^? anions as compared to those formed by TODGA and NO₃^? ions as counter anions. The synergistic effect for U(VI), Th(IV), and Ln(III) extraction from aqueous nitric acid solutions with mixtures of TODGA and HDNNS becomes weaker when the acidity of the aqueous phase increases. A high synergistic enhancement is accompanied with a high selectivity of Ln(III) extraction from nitric acid solutions.     

Synthesis of Extraction Resin Containing N,N,N′,N′-Tetraisobutyl Diglycolamide and its Application for Separation of Sr(II) from Rb(I)

Abstract

A novel Levextrel resin containing N,N,N′,N′-tetraisobutyl diglycolamide (TiBDGA) was synthesized by suspension polymerization of styrene and divinylbenzene and its performance for separation of Sr(II) from Rb(I) was investigated. The effects of crosslink degree, stirring speed, and the ratio of porogenic-agents on the resin synthesized were examined. The optimum TiBDGA resin with 40 wt.% divinylbenzene as cross linking agent and 20 wt.% of n-octanol as porogenic-agents provided excellent adsorption capacity of 22.5 mg/g. The distribution coefficient (K _d) of Sr(II) in HNO₃ media onto the resin depended heavily on the acidity in the aqueous solution. The maximum K _d for Sr(II) (7300 mL/g) was observed when the HNO₃ concentration in aqueous phase reached 2 mol/L. The difference in the Sr(II) and Rb(I) distribution coefficients of several orders of magnitude implied that ⁸⁹Sr may be separated from ⁸⁶Rb with a radionuclide purity greater than 99%. And the maximum static adsorption capacity of Sr(II) on the resin was 22.5 mg/g.     

An Empirical Correlation for Pu(III) Distribution Coefficients in 30% TBP/n‐Dodecane PUREX System in the Presence of U(VI), U(IV), Pu(IV), Pu(III), and Hydrazine Nitrate

Abstract

For modeling and simulation of the partitioning step (either chemical or electrochemical) of the PUREX process, distribution coefficients of the involved species are needed. In this contribution, reported experimental data on Pu(III) extraction under PUREX conditions have been analyzed, and an empirical model is reported. The model reported here is considered more reliable than the model currently available in the literature.     

Extraction Behavior of Am(III) and Eu(III) from Nitric Acid Medium in Tetraoctyldiglycolamide-Bis(2-Ethylhexyl)Phosphoric Acid Solution

The extraction behavior of Am(III) and Eu(III) in a solution of tetra-octyldiglycolamide (TODGA), bis(2-ethylhexyl)phosphoric acid (HDEHP), and n-dodecane (n-DD) was studied to understand the role of TODGA and HDEHP in the combined solvent system. The extraction behavior of these metal ions was compared with those observed in TODGA/n-DD and HDEHP/n-DD. The effect of various parameters such as concentrations of HNO₃, TODGA, and HDEHP on the distribution ratio of Am(III) and Eu(III) was studied. Synergistic extraction of both the metal ions observed at lower acidities (<2.0 M) was attributed to the involvement of TODGA and HDEHP for extraction. However, the extraction of Am(III) and Eu(III) in the combined solvent was comparable with that observed in TODGA at higher acidities. The slope analysis of the extraction data confirmed the involvement of both the extractants at all acidities investigated in the present study.     

Comparison of Extraction Behavior of Neptunium from Nitric Acid Medium Employing Tri-n-Butyl Phosphate and N,N-dihexyl Octanamide as Extractants

Extraction behavior of neptunium has been compared for tri-n-butyl phosphate (TBP) and N,N-dihexyl octanamide (DHOA) extractants as a function of nitric acid concentration (0.5 ? 6 M HNO₃), uranium loading (50 and 300 g/L relevant to Pu rich fast reactor and Pressurized Heavy Water Reactor, PHWR spent fuels, respectively), and in the presence of oxidizing and reducing agents. These studies suggest the possibility of co-recovery of U(VI), Pu(IV) and Np(IV) from spent fuel dissolver solutions (of Pu rich fuels) employing DHOA as extractant.     

Studies on the Separation and Recovery of Plutonium from Nitric Acid Medium using Di-nonyl Phenyl Phosphoric Acid (DNPPA) / n-Dodecane as Extractant System

This paper deals with the studies on the separation and recovery of plutonium from nitric acid medium using Di-nonyl phenyl phosphoric acid (DNPPA) in n-paraffin as an extractant system. The different extraction parameters were investigated. The percentage extraction of plutonium decreased with increase in nitric acid concentration. The optimum solvent concentration for quantitative separation of plutonium from aqueous feed solution was 0.15 M of DNPPA whereas n-paraffin/n-dodecane was the most suitable of diluents with an organic to aqueous phase ratio of 1:1. Among the various strippants used, 0.5 M solution of (NH₄)₂CO₃ was found to be the most suitable for back extraction of plutonium from the loaded organic phase. The developed method was used to separate and recover plutonium from actual wash solution of ion exchange column used for plutonium purification. More than 73% of plutonium was separated from 7 M HNO₃ wash solution using 0.15M of DNPPA in n-dodecane.     

四羟丙基乙二胺–乙二胺四乙酸二钠体系快速化学镀铜

采用四羟丙基乙二胺(THPED)–乙二胺四乙酸二钠(EDTA-2Na)配位体系在环氧树脂板表面进行快速化学镀铜。研究了配位剂、主盐、添加剂和工艺参数等对沉积速率和镀液稳定性的影响,得到快速化学镀镍的最佳镀液配方和工艺条件为:CuSO4·5H2O 12 g/L,THPED 10g/L,EDTA-2Na 5.8 g/L,37%甲醛14 mL/L,2,2′-联吡啶15 mg/L,K4Fe(CN)6 10 mg/L,2-巯基苯并噻唑(2-MBT)5 mg/L,pH 12.5~13.0,装载量3.0 dm2/L,温度40~45°C,时间20 min。在最佳工艺条件下,化学镀铜的沉积速率可达12.7μm/h,镀层表面平整、致密、光亮,背光级数达9级。