Hydrometallurgy Of Uranium Research Articles

Geomechanical stress–strain assessment of enclosing rock mass in backfilling mined-out voids with uranium hydrometallurgy residue

Geomechanical stress–strain assessment of enclosing rock mass in backfilling mined-out voids with uranium hydrometallurgy residue

Extraction and immediate solidification of uranium (VI) using malonamide functionalized ionic liquids from H2SO4 leaching liquor by specific self-assembly process

A novel self-assembly process for simultaneous extraction and solidification of uranium (VI) from H2SO4 leaching liquor was pioneered using malonamide-based distearyldimethylammonium ionic liquids ([D1821]+[MA]−), which exhibited the good affinity and excellent extraction efficiency for uranium compared to 18 main elements, including Ca, Na, K, Al, Mg, Fe, Cu, Se, Sr, W, Mn, Zn, V, Co, Cr, Ba, Pb and Cd in real leaching liquor. The simultaneous separation and recovery of uranium (VI) was firstly realized by the selective self-assembly extraction of complex anion to form the solid by [D1821]+[MA]−, while leaving the other sulfates in aqueous solution. More than 99 % of uranium(VI) was extracted and enriched as self-assembly solid in one-step process, which could be easily recovered by filtration without further stripping and final precipitation. The self-assembly solid was characterized by XPS, FT-IR, 1H NMR, DLS and SEM-EDS methods. Based on the slope analysis and ESI-HRMS data, an unusual extraction mechanism was proposed in three-step process. [D1821]+[MA·UO2SO4]− was confirmed as the predominant component of self-assembly solid. The maximum loading capacity reached as high as 0.52 mol U(VI) per mole of the ionic liquid. The fewer steps, low cost, high extraction efficiency and excellent selectivity endowed the present strategy with the significant value in uranium hydrometallurgy, which could be employed as a potential alternative for recovery of uranium from real leaching liquor.

Study on detoxification behavior of poisoned resin in neutral uranium hydrometallurgy process

Poisoning of ion exchange resin often occurs in uranium hydrometallurgy processes, which reduces or even depletes the adsorption capacity of uranium adsorption. Many regeneration methods have been investigated but their static desorption efficiency is undesirable and only the recovery rate is considered in the selection of regenerant. In this paper, NaClO was selected as an antidote based on a series of investigation indexes. After detoxification by dynamic elution, all performance indexes of the regenerated resin are close to those of the new resin. Compared with static method, reagent consumption and detoxification time can be saved. At the same time of reducing the cost and waste liquid discharge, it also improves the work efficiency.

ГИДРОЛИЗ КОНЦЕНТРИРОВАННЫХ РАСТВОРОВ НИТРАТА КАРБАМИДА

Актуальность исследования обоснована целесообразностью утилизации нитрата карбамида, образующегося в разработанном ранее процессе карбамидной денитрации рафинатов азотнокислого аффинажа урана для предприятий фабрикации ядерного топлива. В данной работе рассматриваются результаты исследования процесса гидролиза нитрата карбамида в нитрат аммония, используемого в гидрометаллургии урана. Объекты: модельные растворы нитрата карбамида с концентрацией 100–500 г/л с добавлением различных реагентов: азотной кислоты, нитрата аммония. Методы: ИК-спектроскопия, рН-метрия, спектрофотометрия, газовая хроматография. Результаты. Изучен процесс гидролиза нитрата карбамида при атмосферном давлении, температурах 70–105 °С, концентрациях исходного раствора 100–500 г/л и с добавлением различных реагентов – азотной кислоты и нитрата аммония. Установлено, что повышение температуры способствует интенсификации процесса гидролиза; добавка азотной кислоты при концентрации 100 г/л замедляет процесс, а добавка нитрата аммония практически не влияет на процесс гидролиза нитрата карбамида. ИК-спектроскопические исследования позволяют сделать вывод о том, что нагревание растворов с исходными концентрациями 100 и 200 г/л при 90 °С в течение 20 часов с отведением выделяющихся газов приводит к полному гидролизу нитрата карбамида. Степень гидролиза нитрата карбамида и степень его конверсии в нитрат аммония совпадают при рН≤7. ИК-спектры совокупно с данными химического анализа подтверждают наличие в продуктах гидролиза нитрата карбамида гидрокарбоната и нитрата аммония. Промежуточных продуктов гидролиза не обнаружено.

Use of Carbamide Nitrate in the Hydrometallurgy of Uranium

The influence exerted by carbamide nitrate additive in the extractive refining of uranium on the capacity of the extractive agent (23% TBP in an organic diluent), completeness of uranium re-extraction from a saturated extractive agent, and residual concentration of uranium in the nitrate raffinate was examined. Nitrate-carbamide and nitrate solutions containing uranyl nitrate [UO2(NO3)2] obtained in the dissolution of concentrated uranium oxide (U3O8) were used in experiments. The re-extraction of uranium was performed with acidified water at pH 3. It was found that the capacities of the extractive agent for uranium are comparable for the nitrate-carbamide and nitrate solutions, which makes it possible to use carbamide nitrate as an agent for salting-out of uranyl nitrate. The residual concentration of uranium in the raffinate after a carbamide denitration does not exceed 13.6–14.1 mg/L. A solution of ammonium carbonate also provides a complete solid-phase re-extraction of uranium from the extractive agent saturated in the nitrate-carbamide solution. There is no accumulation of carbamide nitrate in the technological cycle at an acidity of the starting solution equal to 0.4–0.6 M. The stability temperature is calculated for the system under study. A process of hydrolysis of carbamide nitrate to ammonium nitrate at an elevated pressure is suggested. The resulting solution can be used, after an acidity correction, as a desorbing agent in the sorption refining of uranium in the technology of underground leaching of uranium.

Analysis and processing of sulfate accumulation in uranium hydrometallurgy for acid in-situ leaching

ABSTRACT In order to alleviate the sulfate accumulation in uranium hydrometallurgy process, the sulfate accumulating path was studied and a new elution process was proposed. The eluate composition as a function of eluent volume during the conventional and new elution process was studied. The result showed that pre-elution of saturated resin with 0.5–0.8 BV (bed volume) mother liquor was beneficial to the discharge of accumulated sulfate and could alleviate the accumulation of sulfate. Field tests showed that the new process ensured more stable production and reduced the amount of wastewater. Finally, the mechanism of the pre-elution process was analyzed.

Numerical simulation of flow field and the study of the uniform distribution of fluid in uranium hydrometallurgy fixed bed based on CFD

Uranium hydrometallurgy fixed bed is used to separate and extracting uranium compounds from the leaching of uranium ore. It is a very important equipment in the process of uranium purification. The distribution of the internal flow field of uranium hydrometallurgy fixed bed has great effect on the running efficiency of fixed bed. In this paper, on the basis of fluid mechanics, computational fluid dynamics software Fluent is used to numerical simulation for resin adsorption process in axial flow uranium hydrometallurgy, fixed bed that the diameter is 1600 mm and the height is 6800 mm and to research internal flow field distribution of the fixed bed. The results shows that the fluid distribution in the fixed bed is uneven in the process of adsorbent resin adsorption. The groove shunt filter plate at the exit is a powerful measure to realize the uniform distribution of fluid in the resin layer of fixed bed.

Sorption-extraction processes in uranium hydrometallurgy: Processing of monometallic uranium ores

The method used to develop sorption-extraction processes in uranium hydrometallurgy over the last 50 years is examined. The first-generation sorption-extraction processes, ionites, and apparatus are described. Data for the second-generation sorption-extraction technology and improvement of apparatus are generalized. The third generation of these processes is characterized by the adoption of porous anionites AM-p and AMP-p in order to make the kinetic characteristics of the sorption and extraction processes closer to one another, by sorption leaching of uranium ores, and by adoption of double synergetic mixtures of extracting agents at the stage of repurification of the commercial reclaim and by the development of fast sorption processes for extracting uranium from productive solutions used in mound and underground leaching. The fourth-generation processes are characterized by the use of high-volume vinyl pyridine ionites, tertiary synergetic mixtures at the extraction stage, combined extraction-desorption processes, solid-phase regeneration of saturated ionites, and conversion of absorbed anions of uranyl-trisulfate into nitrate and chloride complexes. 1 figure.

Sorption-Extraction Processes in Uranium Hydrometallurgy: Coextraction of Valuable Components and Dual-Purpose Technology

Sorption-extraction processes for obtaining finished coproducts during processing of uranium ores with valuable components, such as Mo, V, W, Re, Au, Sc, rare-earth elements, Y, Cs, Cu, Ta, Nb, Zr, Hf, Mn, Sn, and Se, are described. Special attention is focused on experience in extraction decontamination of phosphoric acid with its uranium and thorium content decreased by a factor of 20 and obtaining from it ecologically pure phosphate fertilizers and feed phosphates.

Development of advanced technology in the hydrometallurgy of uranium

Almost 50 years of work at the All-Russian Scientific-Research Institute of Chemical Technology on the hydrometallurgy of uranium is surveyed. Autoclave leaching, sorptional pulp processing, and extractional deposition of pure uranium compounds permit the processing of lean uranium ores. Advanced low-waste technologies have been developed, with radical reconstruction of the processing plants.

Solubility of uranous sulfate in aqueous sulfuric acid solution

To provide important thermodynamic data for use in uranium hydrometallurgy, solubilities of uranous sulfate were determined as a function of free acid concentration and temperature. Two sets of experiments were performed in this study. One set was the precipitation experiments of uranous sulfate crystals, in which concentrated uranous sulfate solution was mixed with sulfuric acid solution of suitable concentration. The other set was the dissolution experiments of uranous sulfate crystals in aqueous sulfuric acid solutions. It is noteworthy that good agreement exists between the solubilities determined by the two methods. At elevated temperatures, say, 363 K, the presence of free sulfuric acid is required to avoid precipitation of uranous hydroxide resulting from the hydrolysis of uranous sulfate. Generally speaking, however, an increase in free sulfuric acid concentration results in a slight decrease in uranous sulfate solubility. The elevation of solution temperature causes a decrease in solubility of uranous sulfate. It should be noted that the solid uranous sulfates equilibrated with saturated solutions at 298 K were U(SO4)2 2H2O in dilute sulfuric acid solution and U(SO4)2 4H2O in concentrated sulfuric acid solution, while those at 333 K and 363 K were mainly U(SO4)2 4H2O.

Decantation processes in the hydrometallurgy of uranium

Decantation processes in the hydrometallurgy of uranium

The use of ion-exchange membranes in the hydrometallurgy of uranium

Electrodialysis with ion-exchange membranes is important in chemistry, chemical technology and hydrometallurgy as a basic operation which eliminates the usual chemical neutralization and makes it possible to remove excess acidity and alkalinity, to separate mixtures of elements whose properties are similar and to extract radioactive products from waste waters.

Extraction of uranium from solutions and pulps

Extraction processes are finding increasing application for the processing of uranium from raw materials. The high selectivity and the fluid aggregate state of the extraction agents give this method advantages over the previously known processes. This article gives data on the extraction of uranium from sulfate, nitrate, chloride and phosphate solutions and pulps, most frequently encountered in the hydrometallurgy of uranium. The extraction agents suitable for industrial use are the esters of carboxylic acids, the esters of phosphoric and phosphinic acids and also liquid cationexchange materials and anion-exchange materials, in a number of cases (in the exraction of uranium from colored solutions) have advantages over solid ion exchange materials. A system is described for the extraction of uranium from dense ore pastes.

The flocculation of pulp and polyacrylamide-type flocculents

The processes of dividing hydrometallurgical pulps into solid and liquid phases with subsequent washing out of the dispersed solid particles from the solute are very important in the technology of processing ores and concentrates of uranium, lithium, zirconium, and other metals. Flocculation of pulp, i.e., the formation of more or less large and strong aggregates of particles, is accomplished by special flocculating reagents. Their action facilitates dividing and washing out the solid phase from the solute. This article describes the properties and methods of obtaining the most effective flocculents and gives the results of an investigation of the flocculation processes of aqueous, acid, and carbonaceous hydrometallurgical pulps. The article is of interest for a wide circle of specialists working in industrial enterprises, in factory laboratories, and in research institutes studying the concentration of ores and the hydrometallurgy of uranium and other metals.

Application of sorption and solvent extraction processes in the hydrometallurgy of uranium

This article is a review of those reports presented at the Second International Conference on the Peaceful Uses of Atomic Energy (Geneva, 1958) which dealt with sorption- and solvent-extraction processes in the hydrometallurgy of uranium. It is shown that these methods have been adopted on a relatively wide scale in the industries of the USA. The various forms of application of sorption are discussed, particularly the new processes of uranium recovery by sorption from pulp. Two main classes of extraction solvents are considered: organophosphorus compounds and amines, and the influence of various factors on solvent-extraction processes is also discussed. Examples are given of the application of sorption and solvent-extraction processes in ore-processing plants, and general conclusions are drawn.