A technology for the extraction of zirconium (IV) from solutions of high-level waste, adapted to the existing equipment scheme of the PUREX process, has been developed using the example of model solutions in tributyl phosphate in a hydrocarbon diluent. An experimental simulation of the calculated 5-stage counter-current cascade was carried out, and good agreement between the calculated and experimental results was shown. The methods for re-extraction of Zr4+ from the loaded organic phase were selected, the number of stages of exhaustion of Zr4+ from the loaded organic phase under the selected conditions was calculated. A fundamental technological scheme for the extraction method of zirconium recovery from Eastern Administrative Okrug is proposed which does not require a radical reconstruction of existing high-level nuclear fuel reprocessing facilities.

N,O-donor hybrid heterocyclic extractants have great potential for separation of actinides from lanthanides in spent nuclear fuel reprocessing processes. We demonstrate that this type of reagents can be used for primary concentration of actinides contained in eudialyte, a promising mineral containing a heavy group of lanthanides. With respect to lanthanide ions, the efficiency of their extraction decreases in the series L3 >> L1 > L2, and the extraction of actinides decreases in the series L1 ≈ L3 >> L2. For the extractant L2 based on 2,2′-bipyridine-6,6′-dicarboxylic acid diamide, the efficiency of lanthanide purification from U, Th exceeds 50. The structure and stereochemical features of the ligands do not have a significant effect on the composition of the formed complexes. The solvation numbers are close to 1 for all range f-elements studied, except for thorium, which indicates the predominant formation of complexes with the composition ratio of 1:1. The solvation numbers 1.4–1.5 are observed for thorium(IV), and the established values indicate the formation of a mixture of complexes with the composition ratios of 1:1 and 2:1.

A series of (2–carbamoyl ethyl)diphenylphosphine oxides (KFO) has been synthesized from commercially available reagents — diphenyl chlorophosphine and acrylamides. The influence of the number of ligand fragments of Ph2P(O)(CH2)2C(O), the nature of the oligoyl radical binding these fragments, as well as the presence of additional coordination centers in the KEFO molecule on the extraction properties of KEFO with respect to actinides and lanthanides was investigated. It was found that N,N′-methylene-bis[3-(diphenylphosphoryl) has the greatest efficiency in the extraction of actinidespropionamide] (III), in which two diphenylphosphorylpropionyl radicals are bound by a rigid HNCH2NH linker (the degree of extraction of U(VI) reaches ~73%, and Th(IV) — ~85%), while in the case of lanthanides, on the contrary, ligand V, containing the maximum amount of this kind of phosphoryl carbonyl radicals attached to a conformationally non-rigid nitrogenous heterocyclic matrix, as well as KEFO (II), containing an additional C=O group in an alkyl radical attached to a nitrogen atom, has significant advantages carbamoyl fragment (when using this compound, gadolinium extraction is close to 92%). The obtained data show that highly effective and selective extractants of both 4fand 5felements can be created on the basis of (2-carbamoyl ethyl)diphenylphosphine oxide structure.

New solvent systems for selective separation of palladium from nuclear wastes represent a prospective way to reduce the total waste volume and induce this metal’s extraction. For this purpose, the potential of modern green solvent room-temperature ionic liquid was assessed with diamide-type extractants based on N-heterocycles and S-donating thiodiglicolic acid. The N-donating heterocyclic extractants demonstrate structure-dependent high selectivity toward palladium in the presence of various impurity metals (such as Zr, Cs, Sr, Mo, Ce, Fe, and Cr) from spent nuclear fuel. Palladium is extracted into the organic phase quite selectively with a separation factor greater than a thousand for all extractants. Ionic liquid media are capable of selective palladium separation from platinum group metals and synergetically increase the selectivity of the extractants.

Phosphoryl podands of neutral type with a flexible ethylene glycol chain and diphenylphosphorylmethyl end groups are known for their complexation properties towards various cations. In this work, the complexation process between 1,3-bis(diphenylphosphoryl)-2-oxapropane (L) and lanthanide ions was studied. Namely, the stability constants of lanthanide complexes with L in acetonitrile were estimated by the method of spectrophotometric titration. It was found that the stability constants of Ln3+ complexes with L increase in the lanthanide series, which is consistent with the extraction and ion-selective properties of L. The extraction ability of L and this ligand in the presence of ionic liquids (ILs) such as methyltrioctylammonium nitrate (MTOAN) and bis[(trifluoromethyl)sulfonyl]imide 1-butyl-3-methylimidazolium (C4mimTf2N) was studied. It was found that in the presence of ILs, L extracts the elements of the yttrium subgroup of lanthanides much better than those of the cerium subgroup: SFLu/Ce(L-MTOAN) = 2.29; SFLu/Ce(L-C4mimTf2N) = 110.38. The use of the L-C4mimTf2N mixture in the processes of lanthanide separation into subgroups is much more efficient than the use of L without the addition of ILs or the use of the L-MTOAN mixture. The ion-selective properties of L towards Ln3+ ions were studied. Podand L exhibits potentiometric selectivity to Lu3+ ions. 1,3-Bis(diphenylphosphoryl)-2-oxapropane exhibits selectivity towards the cations of the yttrium subgroup of lanthanides, a lutetium-selective electrode based on this ligand was developed, and Ln extraction was studied.

The possibility of using 5-(diphenylphosphoryl)hexan-3-one as an extractant for efficient recovery of rare-earth metals (REM), as well as uranium(VI) and thorium(IV) from breakdown phosphogypsum solutions within a single technological extraction process was demonstrated. 5-(Diphenylphosphoryl)hexan-3-one as an extractant was compared in terms of efficiency with commercially available TBP and TOPO. It is shown that the complete recovery of rare earth metals into the organic phase is achieved in three stages of depletion. There occurs an extraction purification of total rare earth metals from uranium(VI) and thorium(IV). The separation factor during extraction for U(VI) and ΣREE was f [ΣREE/U(VI)] > 3000, and in the case of thorium(IV), f [ΣREE/Th(IV)] ~10000. 5-(Diphenylphosphoryl)hexan-3-one can be successfully used in the extraction processing of mineral and technogenic raw materials, which enables separation and concentration of REMs.

The total concentrate of heavy lanthanides, zirconium, scandium, as well as emanating uranium and thorium can be recovered from the eudialyte ore concentrate breakdown solutions with help of 5-(diphenylphosphoryl)hexan-3-one within one technological extraction stage. The method makes it possible to separate the components of rare metal raw materials of various origins and generate concentrates suitable for further processing. The proposed new reagent of a series of phosphoryl ketones can be successfully used in the extraction processing of mineral and technogenic raw materials, enabling extraction and concentration of rare earth metals, as well as to separate them from related impurities, in particular, from radioactive uranium, thorium and their decay products.

Effect of structure of phosphorylketones containing flexible alkyl and conformationally rigid fragments in the linker on extraction ability toward actinides and lanthanides has been studied. It has been shown that the introduction of conformationally rigid cycloalkanediyl and alkenediyl fragments in the bridge between P=O and C=O groups in the structure of molecule decreases efficiency of extractants for both actinides and lanthanides. At the same time, the introduction of flexible alkyl groups in linker structure increases complexing and extraction ability. This dependence has been explained theoretically by modeling complexation (DFT, PBE, cc-pVDZ), monodentate coordination was observed for all studied phosphorylalkanones

The optimal conditions for the extraction of U(VI), Th(IV), and La(III) from nitric acid media by phosphorylated acidic podands were determined In this work by varying the length of the polyester chain that binds aromatic fragments; the most effective podand 1,5-bis[o-(hydroxyethoxyphosphoryl )-phenoxy]-3-oxapentane with diethylene glycol chain -(OCH2CH2)2O-. The composition and proposed structure of extractable U(VI) and Nd(III) complexes with 1,5-bis[o-(dihydroxyphosphoryl)phenoxy]-3-oxapentane were studied by physico-chemical analysis methods.

The paper summarizes the results of studies of the complexing properties of phosphoryl ketones with respect to actinides and lanthanides, which makes it possible to identify the most effective and selective ligand of the phosphoryl ketones class, namely 5-(diphenylphosphoryl)hexan-3-one. Using this ligand, the possibility of efficient extraction of rare earth metals, as well as uranium(VI) and thorium(IV) from phosphogypsumleaching solutions within a single stage technological extraction process was demonstrated and the efficiency of using 5-(diphenylphosphoryl)hexan-3-one as extractant with commercially available TBP and TOPO was performed.

The extraction properties of a series of diamides of 2,2-bipyridine-6,6-dicarboxylic acids with respect to americium, curium, neptunium, thorium, light lanthanides and a series of d-elements present in solutions of highly radioactive wastes have been studied in this work. It has been shown that the extraction properties of diamides are determined not only by the structure of the heterocyclic framework, but also by the nature of substituents in positions remote from oxygen centers. The influence of substituents in a series of extractants is determined by differences in their electronic nature, and also depends on their volume and position. In the work, effective and selective extractants were found for the separation of the Am/Eu pair (SF up to 27), and fundamental patterns were revealed between the structure of the extractant and the efficiency of extracting metal ions.

Продемонстрирована возможность использования 5-(дифенилфосфорил)гексан-3-она в качестве экстрагента для эффективного извлечения редкоземельных металлов, а также урана(VI) и тория(IV) из растворов вскрытия фосфогипса в рамках одного технологического экстракционного процесса. 5-(Дифенилфосфорил)гексан-3-он в качестве экстрагента сопоставлен по эффективности использования с коммерчески доступными ТБФ и ТОФО. Показано, что полное извлечение редкоземельных металлов в органическую фазу достигается за три стадии исчерпывания. Происходит экстракционная очистка суммы редкоземельных металлов от урана(VI) и тория(IV). Фактор разделения при экстракции для U(VI) и суммы РЗЭ составил f [ΣРЗЭ/U(VI)] > 3000, а в случае тория(IV) f [ΣРЗЭ/Th(IV)] ~10000. 5-(Дифенилфосфорил) гексан-3-он может успешно применяться при экстракционной переработке минерального и техногенного сырья, позволяя извлекать и концентрировать редкоземельные металлы .

Показана перспективность использования серы в качестве восстановителя при переработке редкометалльного сырья. Рассмотрены варианты тиохлорирования сырья таких редких металлов, как ниобий, тантал, титан, цирконий и гафний. Показана возможность разделения редких металлов на стадии тиохлорирования их минерального сырья. Сопоставлена термодинамика процессов тиохлорирования и карбохлорирования оксидов редких металлов на примере элементов IV-B группы. Рассмотрены вопросы аналитического обеспечения производства редких металлов по хлорной технологии.

Eudialyte-group minerals are of scientific interest as important concentrators of rare elements (mainly Zr and REE) in agpaitic alkaline rocks and a potential source of REE, Zr, Hf, Nb, and Ta for industrial use. Extraction of uranium(VI), thorium(IV), zirconium(IV), hafnium(IV), titanium(IV), and scandium(III) by a binary extractant based on 1,5-bis[2-(hydroxyethoxyphosphoryl)-4-ethylphenoxy]-3-oxapentane and methyl trioctylammonium nitrate from eudialyte breakdown solutions is studied. Extraction isotherms were obtained and exhaustive extraction was investigated. It is shown that uranium, thorium, hafnium, zirconium, scandium, and titanium are almost completely recovered in two-stage extraction by a mixture of 1,5-bis[2-(hydroxyethoxyphosphoryl)-4-ethylphenoxy]-3-oxapentane and methyltrioctylammonium nitrate in 1,2-dichloroethane. Quantitative characteristics were compared for uranium(VI), thorium(IV), zirconium(IV), hafnium(IV), titanium(IV), and scandium(III). It was shown that the extraction efficiency of the metals by the binary extractant based on 1,5-bis[2-(hydroxyethoxyphosphoryl)-4-ethylphenoxy]-3-oxapentane and methyltrioctylammonium nitrate in 1,2-dichloroethane is much higher in comparison with the commercially available tributyl phosphate.

This article provides a survey of wet (aqueous) methods for recovery, separation, and purification of uranium from fission products in carbonate solutions during the reprocessing of spent nuclear fuel and methods for removal of radionuclides from alkaline radioactive waste. The main methods such as selective direct precipitation, ion exchange, and solvent extraction are considered. These methods were compared and evaluated for reprocessing of spent nuclear fuel in carbonate media according to novel alternative non-acidic methods and for treatment processes of alkaline radioactive waste.

Исследованы новые олигодентатные фосфоразотистые соединения. Разработаны методы синтеза этих соединений, а также изучены их комплексообразующие и экс- тракционные свойства по отношению к актинидам и лантанидам. Показано, что введение дополнительной координирующей группы к катиону металла приводит к значительному росту экстракционной способности актинидов. Представленные исследования могут быть основанием использования олигодентатных фосфоразоти- стых соединений в качестве реагентов для экстракционного и хроматографического разделения и концентрирования актинидов и лантанидов из различных сред.

A technique has been developed for the semi-empirical calculation of the product yield in the redox reaction of nitric acid with uranium and its oxides of various compositions, as well as with iron. The proposed technique makes it possible to obtain technological data upon dissolution of spent nuclear fuel, and also upon additional voloxidation of irradiated fuel with a lack of analysis data. The method of using material balance equations was demonstrated to control the reliability of experimental and technological results, as well as the reliability of analytical control.

N -Diphenylphosphoryl- N '-[ω-(alkoxy/tetrahydrofuryl)alkyl]ureas have been synthesized based on a highly efficient one-pot catalytic process and their extraction properties have been studied with respect to f -elements in nitric acid media. The influence on the extraction characteristics of the presence of an alkoxy or tetrahydrofuryl group located in the ω-position of the normal N '-alkyl radical of phosphorylurea has been revealed. It has been shown that N -(diphenylphosphoryl)urea containing N '-[2-(tetrahydrofur-2-yl)ethyl] radical has the best extraction properties with respect to the studied f -elements, especially this effect is pronounced for uranium(VI). This dependence has been theoretically substantiated when simulating complex formation by the density functional theory method (DFT, PBE, cc-pVDZ), since the coordination of the f ‑element ion to the oxygen atom of the furyl radical attached to the ethylene carbon chain turns out to be preferable.

The results of experiments are presented on testing the separation of uranium from U-Be nuclear fuel solutions by extraction. It was shown that the degree of uranium extraction using a solution of 10 vol% TBP in RED-3 from a nitric acid solution of this fuel is 98.7%. Transfer of uranium into the re-extract is 97.9%. More than 99.99 % of beryllium goes into the extraction raffinate intended for further vitrification. The results of the study were used for the preparation of technological regulations on reprocessing of U-Be SNF at the RT-1 plant of the Mayak Production Association. The industrial-scale reprocessing of this fuel confirmed the values determined in the study.

Проведено квантово-химическое моделирование структуры N-дифенилфосфорил-N’-( ω-алкил)мочевин на основе расчета молекулярных электростатических полей. Разработан высокоэффективный технологичный one-pot-синтез и синтезиро- ваны N-дифенилфосфорил-N’-(ω-алкил)мочевины. Исследованы экстракцион- ные свойства по отношению к f-элементам в азотнокислых средах. Показано, что N’-алкилзамещенные N-дифенилфосфорилмочевины являются высокоэффектив- ными экстрагентами, способными извлекать актиноиды и лантаноиды из азотнокис- лых растворов с высокими коэффициентами распределения, существенно превос- ходя при этом известные нейтральные моно- и бидентатные фосфорорганические экстрагенты различных типов.