Solvent extraction of nitric acid,uranium（VI） and thorium（IV） by N,N,N‘,N’—tetrahexylsuccinylamide

A new kind of diamide N,N,N‘,N‘-tetrahexylsuccinylamide(THSA) was synthesized,characterized and used for the extraction of HNO3,U(VI)and Th(IV) in a diluent composed of 0.5 volume fraction 1,2,4-trimethy benzene(TMB) and 0.5 volume fraction kerosene(OK),Extraction distribution coefficients of U(VI) and Th(IV) as functions of aqueous nitric acid concentation,extractant concentration.temperature and salting-out agent (LiNO3) have been studied,and it is found that THSA as an extractant is superior to TBP for extraction of U(VI) and Th(IV),Back Extraction was also studied.At low acidity,the main adduct of THSA and NHO3 is HNO3 is HNO3.THSA,THSA.(HNO3)2 and THSA.(HNO3)3 are also found at high acidity.The compositions of extracted species.apparent equilibrium constants and enthalpies of extraction reactions have also been calculated.     

Solvent extraction of uranium(Ⅵ)and europium(Ⅲ)from nitrate media by picolinamide

The solvent extraction of uranium(Ⅵ) and europium(Ⅲ) from nitric acid solution was studied with picolinamide dissolved in ethylene dichloride. The distribution ratios of U(Ⅵ) and Eu(Ⅲ) as a function of aqueous HNO3 concentration, extractant concentration in organic phase and temperature as well as the salting-out agent concentration have been measured. The experiment results show that picolinamide has higher extractability for U(Ⅵ1)than for Eu(Ⅲ). The composition of extracted species, equilibrium constants and enthalpies of extraction reaction have also been presented.     

Solvent Extraction of Np (V) with CMPO from Nitric Acid Solutions Containing U (VI)

The extraction of Np(V) in the presence of U(VI) or Nd(III) was studied with 0.2 M CMPO- decalin and with 0.2 M CMPO-1.4 M TBP-n-dodecane. Distribution ratios of Np(V) decreased with increasing the concentration of Nd(III), which was considered to be explained by the decrease in the concentration of free CMPO. On the other hand, distribution ratios increased as the concentration of U(VI) increased. The absorption spectrum of Np(V) in organic solution showed a new absorption peak which was probably attributable to the formation of cation-cation complexes of Np(V) and U(VI). Assuming the formation of cation-cation complexes, the dependence of distribution ratio of Np(V) on the concentration of U(VI) was found to be semi-quantitatively explained.     

A study on selective precipitation ability of cyclic urea to U(VI) for developing reprocessing system based on precipitation method

We have proposed a new reprocessing system based on precipitation method. In order to find out precipitants with high selectivity to U(VI) and to investigate factors controlling precipitation ability to U(VI) and U(IV), properties of 3,4,5,6-tetrahydro-1,3-dimethyl-2(1H)-pyrimidinone (DMPU) as a precipitant have been examined by using U(VI), U(IV) as a simulant of Pu(IV), and simulated fission products (FPs). We have evaluated precipitation ratios (P.R.) for U(VI) and U(IV), solubility of U(VI) precipitates to 3.0 mol dm^?3 (M) HNO₃ solution, melting points (MPs) of U(VI) precipitates, log P (distribution ratio of a substance in 1-octanol/water biphasic system, a measure of hydrophobicity) of precipitants, and decontamination factors (DFs) of FPs. The properties of DMPU were compared with those in systems using N-n-butyl-2-pyrrolidone (NBP), N-cyclohexyl-2-pyrrolidone (NCP), and other pyrrolidone derivatives as the precipitant. The P.R. values of DMPU to U(VI) and U(IV) in 3.0 M HNO₃ solutions were around 99% at [DMPU]/[U(VI)] = 2.0 and 0% at [DMPU]/[U(IV)] = 5.0, respectively. In DMPU system, the DF values of the most of simulated FPs [Rb(I), Cs(I), Sr(II), Ba(II), Ru(III), Rh(III), La(III), Ce(III), Pr(III), Nd(III), and Sm(III)] used in the present study were found to be more than 100. Even in U(VI)–U(IV) coexisting system, the selectivity of DMPU to U(VI) was higher than those of NBP and NCP. This selective precipitation ability of DMPU to U(VI) was evaluated by the solubility of U(VI) precipitates on the basis of their MPs and the log P values of precipitants. As a result, it was found that the precipitants having low hydrophobicity and forming the U(VI) precipitates with high MPs have highly selective precipitation ability to U(VI).     

Synergistic extraction of U（VI） and Th（IV） from nitric acid media with HBMPPT and TBP in toluene

The sysnergistic extraction of U(VI)and Th(IV) from nitric acid solution by HBMPPT(4-benzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-thione) and TBP( tributylphosphate)in toluene was studied.The extraction ability of HBMPPT for U(VI) and Th(IV) was not so high.but when a little TBP was added in,the ability to extract U(VI) and Th(IV) was improved.The extracted complexes may be presented as UO2NO3.BMPPT.TBP and UO2(BMPPT)2.TBP for U(VI).and Th(NO3)3.BMPPT.TBP and Th(NO3)2(BMPPT)2.TBP for Th(IV),respectively,in the synergistic extraction system.The synergistic effect of HBMPPT and TBP makes the separation cofeeicient of U(VI)/Th (IV) or U(VI)/Eu(Ⅲ) reach a high value.     

Solvent Extraction of Americium(VI) by Tri-n-Butyl Phosphate

Solvent extraction of Am(VI) by tri-n-butyl phosphate (TBP) from nitric acid solutions was investigated to develop a novel method for partitioning americium from high level liquid waste generated through spent nuclear fuel reprocessing. Am(VI) was prepared using ammonium peroxodisulfate and silver nitrate. The distribution coefficients of Am(VI) were determined for extraction systems of various concentrations of nitric acid and TBP. Sufficiently stable Am(VI) could be extracted and the extraction reaction of Am(VI) was found to be the same as for other hexavalent actinides. The apparent equilibrium constant varied with the concentration of peroxodisulfate used for the valence control, which was ascribed to the competitive reaction of the extraction of Am(VI) and the complex formation of Am(VI) with sulfate ion produced by the decomposition of peroxodisulfate. A distribution coefficient of Am(VI) above 1 was obtained with undiluted TBP and the separation factor between Am(VI) and Nd(III) was 87±9. TBP extraction of Am(VI), after implementing valence control, was proved to be an effective method for the partitioning of americium from fission products such as rare earth elements.     

A Nuclear Magnetic Resonance Study on Ligand Exchange Reactions in La(III), Nd(III), and U(VI) Nitrato Complexes with n-Octyl(pheny1)-N,N-Diisobutylcarbamoylmethylphosphine Oxide in Non-aqueous Solvents

The exchange reactions of n-octyl(pheny1)-N, N-diisobutylcarbamoylmethylphosphine oxide (CMPO) in La(III), Nd(III), and U(VI) nitrate complexes with CMPO (La(III)-, Nd(III)-, and U(VI)-CMPO complexes) have been studied in CD₃COCD₃ by means of ³¹P NMR method. The number of CMPO coordinated to the first coordination sphere of La(III) ion was directly determined to be 3 by the area integrations of ³¹P NMR signals of free and coordinated CMPO molecules. The same coordination number of 3 was also obtained for the U(VI)-CMPO complex. The coordination number was not determined for the Nd(III)-CMPO complex, because of its paramagnetic behavior. The exchange rate constants of CMPO in La(III)- and U(VI)- CMPO complexes were obtained by the two-site exchange model. Paramagnetic line broadening was observed in the Nd(III)-CMPO complex and the rate constant for the exchange of CMPO was determined by the line-broadening method. The exchange rates of CMPO in La(III)- and Nd(III)-CMPO complexes depend on the free CMPO concentration ([CMPO]), while that in U(VI)-CMPO complex is independent of [CMPO]. The dissociative (D) and dissociative interchange (I_d ) mechanisms were proposed for the exchange reactions in the La(III)- and Nd(III)-CMPO complexes, and dissociative (D) or I_d mechanism was proposed for the U(VI)-CMPO complex. The dissociative rate constants (s^?1) at 25°C and activation parameters ΔH^# (kJ·mol^?1) and ΔS^# (J·K^?1·mol^?1) are 4.76x10³, 28.7±0.1, ?78.4±0.2 for La(III)-CMPO complex, 4.72x10³, 42.6±0.4, ?31.7±1.3 for Nd(III)-CMPO complex, and 3.20x10³, 46.9±0.6, ?20.5±2.2 for U(VI)-CMPO complex, respectively.     

Studies on the extraction of uranium (VI) by bis (hexylsulfinyl) ethane

The extraction of uranium (VI) by bis(hexylsulfinyl)ethane(BHxSE) in nitric acid aqueous solution has been investigated. The extracted species appeared to be UO2(NO3)2-2BHxSE. Influences of nitric acid concentration, NaNO3 concentration, Na2C2O4 concentration and temperature on the extraction equilibrium were investigated and the thermodynamic functions of the extraction reaction were obtained.     

Extraction of U（VI） and Th（IV） with a novel extractant N,N‘—tetrahexylmalonamide （THMA） in toluene

The dependence of THMA extraction behaviour for U(VI) and Th(IV) on nitric acid concentration,THMA concentratioin and molecular structure of extracted complex has been studied.For nitric acid solutions of 3.0 mol/L a coordinative mechanism may possibly dominate in the extraction of metal catioins,The complex composition of UO2(NO3)2(THMA)2,Th(NO3)4(THMA)2 and Th(NO3)4(THMA03 are proved.     

U(Ⅵ)电还原反萃动力学研究——Ⅱ.U(Ⅵ)反萃和U(Ⅳ)萃取动力学

本文在带有阴阳极的恒界面池中研究了HNO_3-N_2H_5NO_3(H_2O)/UO_2(NO_3)_2-HNO_3(30％TBP-煤油)体系在U(Ⅵ)电解还原过程中的U(Ⅵ)反萃和U(Ⅳ)萃取动力学。这是U(Ⅵ)电还原反萃动力学研究的第二步。根据实验结果和数据处理,得到U(Ⅵ)反萃和U(Ⅳ)萃取过程的表观活化能分别为36.02kJ/mol和21.13kJ/mol;U(Ⅵ)反萃和U(Ⅳ)萃取速率随两相搅拌速率的增大而增大;U(Ⅵ)反萃和U(Ⅳ)萃取过程均由扩散控制。随着阴极电位的降低,U(Ⅵ)反萃和U(Ⅳ)萃取速率均增大。     

Preparation of N, N''''-diacylpiperazine and its extraction property for U(Ⅵ)

1 INTRODUCTIONDuring the last fOrty years) many llteratures about talde have been published.AAnde has been redoned as an alternative to TBP fOr the reprocessing of spent nuclearfu.l.[1~5] They not only can selectively extract U(Vl) effectively from aitric acid media,but also has a lOt of advantages comPared with TBP, such as their comPlete incinerabil-ity, innOalous degradation products, easier preparation and back extraction. However,when the acidity or the content of U(Vl) is hig…     

Extraction of uranyl（VI）ion with N,N—dibutyloctadecanamide from nitric acid solution

The extraction of U(VI) with newly synthesized long chain alkyl amide,N,N-dibutyloctadecanamide(DBODA),has been studied.The dependence of the extraction on nitric acid concentration,DBODA concentration and temperature from nitric acid solution has been investigated and the extracted species has also been investigated using FT-IR spectrometry.The related thermodynamic functions were calculated.The separation factor between U(VI) and Th(IV) is higher and there is no third phase formation under the conditions studied.     

锕系、镧系元素分离中新萃取剂的研究(II)——HCBMPPT对铀(VI)的萃取机理研究

研究了4-(邻氯苯甲酰基)-2,4-二氢-5-甲基-2-苯基-3H-吡唑硫酮-3(HCBMPPT)在硝酸介质中对铀(VI)的萃取行为,并对萃取配合物的化学组成及萃取机理进行了分析和讨论。实验结果表明,其萃取分配比随萃取剂浓度及pH值的升高而增大。     

The Application of an Advanced Ion Exchange Process to Reprocessing Spent Nuclear Fuels, (I)

In order to develop an advanced ion exchange process for the reprocessing of spent nuclear fuels, a novel anion exchanger, AR-01 with the resin embedded in porous silica beads and benzimidazoles as functional groups has been manufactured. Adsorption behavior of various fission product elements (FPs) and uranium in nitric acid medium were investigated experimentally using this anion exchanger. Separation performance of FPs from U(VI) in simulated spent fuel solutions was demonstrated by column chromatography utilizing dilute HNO₃ and thiourea as eluents.

Most FPs such as Cs(I), Sr(II), Mo(VI), Rh(III) and trivalent rare earths showed negligibly slight adsorption and could be separated from U(VI) satisfactorily. Cerium(IV) was strongly adsorbed, but was gradually reduced to non-adsorptive Ce(III) by the anion exchanger. Zirconium(IV) presented weak adsorption and its a part mixed with U(VI) in the column experiments. Ruthenium(III) exhibited quite strong adsorption in a broad HNO₃ concentration range as the form of anionic nitrosylnitrato-complexes, its most amount mixed with U(VI). Palladium(II) showed significantly strong adsorption probably due to complexes formation with the anion exchanger. The adsorbed Pd(II) was effectively eluted out by thiourea and separated from U(VI) and other FPs completely.     

Coextraction of uranium(VI) from nitric acid solutions by N,N-diethyldecanamide and TBP

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The n-Octyldodecylsulfoxide(ODSO)-carbon tetrachloride extracting uranium(VI)

1 INTRODUCTIONfbi-n-butyl phosphate (TBP) has been used for several decades as the most successful extractant for recovery of uredum from spent nuclear fuel (of. Purex Process).However, there are two major disadvantages: (1) The selectivity is not high, and (2)radiolytic degradations of TBP give rise to mono and dibutyl phosphates which increasethe extraction of fusion products resulting in a decrease in the overall decontaminationfactors obtained[1]. Therefore, it is necessary to sear…     

双-丁二酰胺萃取剂对硝酸体系中Th(Ⅳ)的萃取

研究了双-丁二酰胺萃取剂的合成及其对硝酸介质中Th(Ⅳ)离子的萃取行为。从简单的原料出发，合成了新型的多官能团的双-丁二酰胺萃取剂，并以其为萃取剂、二甲苯为稀释剂，考察了水相中硝酸浓度、萃取剂浓度、盐析剂浓度等因素对Th(Ⅳ)离子分配比的影响。利用斜率分析方法提出了双-丁二酰胺萃取剂萃取Th(Ⅳ)的萃取机理。利用该萃取剂对比萃取了钍及铕离子，得到了高达166.6的分离因子。     

Precipitation ability to U(IV) and stability of 1,3-dimethyl-2-imidazolidone for selective precipitation of U(VI) in nitric acid media

As a part of the investigation of precipitants with selectivity to U(VI) in nitric acid media, a preliminary study on the precipitation ability of 1,3-dimethyl-2-imidazolidone (DMI) to U(IV), a simulant of Pu(IV), was performed. DMI is a ring compound like N-n-butyl-2-pyrrolidone (NBP) which is one of the pyrrolidone derivatives (NRPs) and a promising precipitant for U(VI). While DMI is known to precipitate U(VI) from 3 mol dm⁻³ (=M) HNO₃, no precipitate was observed in the solution containing 0.15 M U(IV) and 3 M HNO₃ by adding DMI at the ratio of [DMI]/[U(IV)] = 5. This indicates that the selectivity of DMI to U(VI) than U(IV) is much higher compared with that of NBP.On the other hand, the stability of DMI under γ-ray irradiation and heating in HNO₃ solutions (≤4 M) was also examined to evaluate the applicability of DMI to the practical process, because gradual acid hydrolysis of DMI is inevitable due to the nature of the chemical structure. As a result, it was found that the stability is strongly affected by the concentration of HNO₃. Namely, very few DMI in 2 M HNO₃ underwent the ring-opening by the irradiation up to 220 kGy and heating at 50 °C up to 5 h, respectively, indicating that these treated samples may still hold the precipitation ability to U(VI). On the contrary, the cleavage of the ring of DMI in 4 M HNO₃ was found to proceed easily. From the above results, it was concluded that DMI may be a candidate as a selective precipitant for U(VI) in HNO₃ solutions up to ca. 2 M.     

Separation of Am(III) from Eu(III) by extraction based on in situ extractant formation of dithiocarbamate derivatives

A new solvent-extraction technique based on in situ formation of dithiocarbamate derivatives in order to separate Am(III) from Eu(III) was carried out. In this technique, the extractant is formed during the extraction course by the reaction between the organic materials, which are needed to synthesize the extractant. The synthesis of extractant in in situ extractant-formation method was carried out as follows. Di-substituted amine, such as dioctylamine (DOA), dibenzylamine (DBzA) and so on, and carbon disulfide (CS₂) were mixed in organic solvents, such as nitrobenzene, to produce dioctylammonium dioctyldithiocarbamate (DOA⁺·DODTC⁻), dibenzylammonium dibenzyldithiocarbamate (DBzA⁺·DODTC⁻), or so on. These organic solutions are also the organic phase in the solvent extraction, whereas the aqueous phase is 1.00 mol/dm³ (H, Na)NO₃ solution. The elements of Am(III) and Eu(III) were extracted into organic phase from different hydrogen ion concentrations of aqueous phase. The SF of Am(III)/Eu(III) is 3.2 × 10⁴ at pH_eq = 6.25 in DOA–CS₂/nitrobenzene system. This separation technique of Am(III) from Eu(III) by extraction based on in situ extractant formation has the following advantages. (a) It is unnecessary to take the chemical stability of extractant into account for storage purpose, and (b) Am(III) can be completely separated from Eu(III) by a single extraction procedure.     

锕系、镧系元素分离中新萃取剂的研究(III)——新萃取剂HMBMPPT的合成及其对铀(VI)的萃取研究

通过酰基化、氯化、硫化反应合成了新的酰代吡唑硫酮,即4-(4-甲氧基)-苯甲酰基-2,4-二氢-5-甲基-2-苯基-3H-吡唑硫酮-3(HMBMPPT)。产物的结构用红外、氢核磁共振谱、质谱、元素分析及X射线衍射进行了表征。研究了以氯仿为溶剂HMBMPPT 在硝酸介质中对铀(VI)的萃取行为,考察了稀释剂、萃取剂浓度、酸度、温度及盐析剂浓度对分配比的影响。同时,对萃取配合物的化学组成及萃取机理也进行了分析和讨论。