Uranium Extraction Efficiency Research Articles

Constructing amidoxime-modified porous adsorbents with open architecture for cost-effective and efficient uranium extraction.

The dense structure of polymeric matrices exposes only 10–20% of adsorption (amidoxime) groups, thus detracting from the extraction efficiency of uranium from seawater. Herein, the amidoxime-modified building units were cross-linked via the Scholl reaction into porous aromatic frameworks (PAFs). Due to the formation of open architecture, PAF adsorbents reveal a larger utilization ratio (>60%) of amidoxime groups. Consequently, PAF samples enable an ultrahigh uranium capacity of 702 mg g−1, which creates a 16-fold capacity enhancement and gains a 7-fold adsorption rate improvement compared with polymer-based adsorbents. Notably, PAF solids are able to be integrated into various devices, thus realizing versatile and efficacious uranium extraction from real seawater (meeting the commercial standard ∼6 mg g−1 in 21 days). In addition, the final cost using our PAF-based adsorbent is US $189.77 per kg uranium, it is in accordance with the prevailing market cost ($100–335 per kg).

Physicochemical Features of the Reaction of Eudragit® Fibers with Uranyl Ion in Process Solutions

The reaction of uranyl ion with Eudragit® copolymers was studied. The solution composition was shown to affect the uranium extraction efficiency by the examined polymers. Spectral data confirmed the formation of stable compounds of uranyl ion with Eudragit® E and Eudragit® RS.

Leaching of El-Missikat low-grade fluoritized uranium ore by sulfuric acid: mechanism and kinetic

A well-characterized low-grade fluoritized uranium samples from new occurrence in Gabal El-Missikat prospect, Eastern Desert, Egypt was subjected to sulfuric acid leaching. The effects of leaching parameters on uranium dissolution mechanism were investigated. The shrinking core model was used to model leaching reactions. The kinetics equations indicates that the reactions appear to be controlled by layer diffusion process. The activation energy for uranium dissolution was evaluated. Low activation energy value (2.54 kJ mol−1) confirm the diffusion layer mechanism. The presence of fluoride ions in the solution increases the dissolution of uranium. The optimum process operating parameters were: sulfuric acid concentration: 1.5 M, solid–liquid ratio: 1:3, contact time 8 h; agitation speed rate 200 rpm; and ore particle size − 75 µm at temperature 60 °C, in the absence of an external oxidant. Under these experimental conditions, the extraction efficiency of uranium was about 91%.

Experimental study on hold-up, characteristic and slip velocities in a horizontal pulsed sieve-plate column and uranium reactive extraction condition in aqueous phase

The uranium extraction efficiency from sulfate leach liquor and the hydrodynamic behavior of the reactive extraction system was studied in the horizontal pulsed sieve-plated column. The effects of operating parameters and reactive condition were investigated. The obtained results showed that an increase in pulse intensity caused the decrease of dispersed phase hold-up and increase slip velocity. The slip velocity in the reactive uranium extraction situation was greater than that of the system without the reactive extraction due to the faster upward movement and more buoyancy of drops. The uranium extraction efficiency has a direct relationship with increasing pulse intensity and the dispersed phase flow rate, whereas has an indirect relationship with increasing continuous phase flow rate. Also, with comparison between experimental results and several empirical correlations for characteristic velocity, the Pratt model was chosen for prognostication of this parameter. The experimental results compared with the proposed correlations obtained from the previous studies demonstrated that the previous correlations have any reasonable accuracy to prognosticate the hold-up as well as the characteristic and slip velocities in this column. Therefore, the semi-empirical correlations were determined for prediction of hydrodynamic parameters as functions of the physical properties of systems and operating conditions. It can also be concluded that the horizontal pulsed sieve column is suitable for extraction of uranium from the sulfate liquor by Alamine 336 with extraction efficiency of approximately 99%. Therefore, it is a good alternative in radioactive processes, especially in places with height limitation.

Extraction of uranium and transuranium elements with tert-butylthiacalix[4]arene from carbonate-alkaline solutions

Extraction efficiency of uranium and transuranium elements (Np, Pu, Am and Cm) with tert-butylthiacalix[4]arene TCA from carbonate-alkaline solutions is studied and compared with that of europium (III). Plutonium (III, IV) extraction efficiency with TCA is found to be lower comparing with that of trivalent americium and europium. Extraction efficiency of studied radionuclides decreases as following: Am ≫ Eu ≫ Pu (III), U(VI), Np (V) > Pu (IV) at pH 12. Carbonate concentration increase in aqueous phase suppresses significantly extraction of all studied radionuclides, except americium. This condition can be used for americium individual recovery from complex radioactive carbonate-alkaline solutions.

Simulation of the dynamic beyond-design-basis regime in an extraction–scrubbing unit consisting of mixer–settlers or centrifugal contactors in reprocessing spent nuclear fuel from nuclear power plants and of impurex process

The possibilities of calculating several successive perturbations without time restriction caused by reaching the steady state and of taking into account the uranium extraction efficiency in the steady state of the cascade operation in adjacent steps of the uranium concentration front were introduced into the algorithm for calculating the transient extraction regime in the Purex process. The results of long-term experiments concerning transient regime of the head mixer–settler unit of the RT-1 complex were reconsidered as applied to reprocessing of spent nuclear fuel (SNF) from WWER (water-cooled water-moderated energy reactor), and good agreement of the experimental data and calculation results for beyond-design-basis regime was reached using the model of ideal mixing in a settling chamber without corrections for the efficiency of the step. The effect of significant extraction of Pu at limiting loading of the solvent with uranium was confirmed. Consideration of this effect allowed adequate description of the Pu accumulation in the uranium-free zone of the extraction–scrubbing unit. The adequacy of the ideal mixing model for a unit of centrifugal contactors was demonstrated as applied to reprocessing of SNF from fast reactors, although the difference between the calculation results obtained using the ideal mixing and plug-flow models becomes considerably smaller. A separate experiment has shown that the Pu accumulation in the uranium-free zone does not occur in this case because of higher acidity of the aqueous phase and higher process temperature, and the Pu distribution between the contactor steps correlates with the U distribution. Comparison of the result of the calculation using the corrected model with the results of step-by-step sampling demonstrated the possibility of complete recovery of Pu(IV) in the beyonddesign- basis (with respect to U) regime at lower values of the HNO3 concentration and temperature than it was assumed previously on the basis of published data.

Highly efficient extraction and selective separation of uranium (VI) from transition metals using new class of undiluted ionic liquids based on H-phosphonate anions

In this paper, we report the development of an environmental friendly process to decontaminate uranium-containing ores and nuclear wastes by using non-fluorinated ionic liquids (ILs). The main advantages of this extraction process are the absence of any organic diluent and extra extraction agents added to the organic phase. Moreover, the process is cost-effective and maybe applied as a sustainable hydrometallurgical method to recover uranium. The distribution ratio (DU) and the extraction efficiency (%E) of uranium(VI) (UO22+) were found to be dependent on the acidity of the aqueous phase, the extraction time, the alkyl chain length in the ILs, the concentration of the aqueous feed and molar quantity of ILs. The DU value is higher than 600 and the %E is equal to 98.6% when [HNO3]=7M. The extraction reactions follows a neutral partition or ionic exchange mechanism depending on nitric acid concentration. The nature of bonding in the extracted complexes was investigated by spectroscopic techniques. The potential use of Mor1-8-OP for the separation of UO22+ from a mixture containing transition metal ions Mn+ was also examined. The UO22+ ions were separated and extracted efficiently. These ILs are promising candidates for the recovery and separation of uranium.

Investigation of liquid extraction and thermodynamic studies on uranium from sulfate solution by Alamine 336 as an extractant

This paper presents a comprehensive study of the liquid–liquid extraction of uranium from 0.2 M sulfuric acid solution by tertiary amine (Alamine 336) and kerosene as an extractant and a diluent, respectively. For this purpose, the effects of operating parameters on the uranium extraction efficiency such as Alamine 336 concentration, contact time, initial aqueous phase pH, sulfate ion concentration, temperature and stripping process by different agents are investigated. The Gibbs energy change (ΔG), enthalpy change (ΔH) and entropy change (ΔS) have been determined as thermodynamic parameters to prove exothermic and spontaneous reaction. Also, equilibrium constants, reaction equation and stoichiometric coefficients for uranium extraction with Alamine 336 in sulfate medium are specified. The proposed procedure can be applied to the recovery of uranium from low-grade ore processing and from wastewater in the different stages of the nuclear fuel cycle.

Solubility of tri-iso-amyl phosphate in supercritical carbon dioxide and its application to selective extraction of uranium

ABSTRACTThe solubility of tri-iso-amyl phosphate (TiAP) in supercritical carbon dioxide (SCCO2) was determined at 313–333 K with pressure ranging from 10 to 25 MPa. The solubility data of TiAP in SCCO2 medium were correlated using four semi-empirical models. Selective extraction of uranium from simulated dissolver solution was demonstrated using SCCO2 modified with TiAP. The extraction efficiency of uranium was found to be 95 ± 5%. The influence of temperature, pressure and acidity on the extraction of uranium was studied. An attempt was made to explain the plausible extraction mechanism.

Supercritical fluid extraction and purification of uranium from crude sodium diuranate

Supercritical Fluid Extraction (SFE) and purification of uranium, from crude sodium diuranate (SDU) containing uranium (53%), iron (22.2% of U) and rare earth impurities (4% of U), has been studied. Adduct of tri-butyl phosphate (TBP) and nitric acid (HNO3) has been used for uranium dissolution and extraction. Carbon dioxide has been used as supercritical fluid. For 200mg of crude SDU, operating parameters such as temperature, pressure, quantity of TBP·HNO3 adduct, static and collection time have been optimized at 323K temperature, 15.20MPa pressure, 1mL of TBP·HNO3 adduct, 20min. static time and 20min. collection time. Under these conditions, uranium extraction efficiency was 95±5%. Addition of free nitric acid leads to improvement in purity of uranium. Uranium was stripped from SFE extract and precipitated as ammonium diuranate (ADU), which was then subjected to second cycle of SFE. After two cycles of SFE, purification factor of uranium was found to be 4970, 90, 110 and 60 with respect to iron, yttrium, ytterbium and erbium respectively.

Uranium Extraction by a Bifunctional Amido-Phosphonic Acid: Coordination Structure and Aggregation

ABSTRACTButyl-N,N-di(2-ethylhexyl)carbamoyl-nonylphosphonate (DEHCNPB) is a new amido-phosphonic acid bifunctional ligand with a high uranium extraction efficiency from wet phosphoric acid. In the present work, the DEHCNPB coordination structure toward uranium and its aggregation properties have been fully characterized using experimental and theoretical approaches. DEHCNPB forms associated species, and its aggregation properties such as aggregation number or CAC have been determined from SAXS and SANS measurements. The preferred site for bonding of DEHCNPB toward U(VI) has been determined from IR, EXAFS, and DFT calculations.

Application of response surface methodology to optimize uranium biological leaching at high pulp density

Abstract The aim of the present study was to carry out uranium bioleaching via optimization of the leaching process using response surface methodology. For this purpose, the native Acidithiobacillus sp. was adapted to different pulp densities following optimization process carried out at a high pulp density. Response surface methodology based on Box-Behnken design was used to optimize the uranium bioleaching. The effects of six key parameters on the bioleaching efficiency were investigated. The process was modeled with mathematical equation, including not only first and second order terms, but also with probable interaction effects between each pair of factors.The results showed that the extraction efficiency of uranium dropped from 100% at pulp densities of 2.5, 5, 7.5 and 10% to 68% at 12.5% of pulp density. Using RSM, the optimum conditions for uranium bioleaching (12.5% (w/v)) were identified as pH = 1.96, temperature = 30.90 ℃, stirring speed = 158 rpm, 15.7% inoculum, FeSO4 · 7H2O concentration at 13.83 g/L and (NH4)2SO4 concentration at 3.22 g/L which achieved 83% of uranium extraction efficiency. The results of uranium bioleaching experiment using optimized parameter showed 81% uranium extraction during 15 d. The obtained results reveal that using RSM is reliable and appropriate for optimization of parameters involved in the uranium bioleaching process.

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 < phosphonates < HDEHP < TOPO < 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.

Supercritical fluid extraction of uranium and thorium employing dialkyl amides

N,N-dialkyl aliphatic amides with varying alkyl groups viz. N,N-dibutyl-2-ethyl hexanamide (DBEHA), N,N-dibutyl-3,3-dimethyl butanamide (DBDMBA), N,N-dihexyl octanamide (DHOA), N,N-di-sec-butyl pentanamide (DBPA), N,N-dibutyl octanamide (DBOA), have been evaluated for supercritical fluid extraction (SFE) of uranium and thorium from nitric acid medium as well as from tissue paper matrix. The trend in extraction efficiency could be correlated to the structure of the amides and the amide complex of uranium/thorium. Straight chain amide DBOA was found suitable for SFE of both uranium and thorium. Under optimised conditions (200atm. pressure, 323K temperature, 30min static time followed by 30min dynamic time, 0.5M amide in methanol), (94±3)% uranium and (85±4)% thorium could be extracted from 4M nitric acid medium. For tissue paper matrix, under optimised conditions (200atm pressure, 323K temperature, 45min static time followed by 30min dynamic time, 0.2M amide in methanol) (87±7)% uranium and (88±7)% thorium were extractable. For the amide having branching at Cα, DBEHA, extraction efficiency of thorium was as low as 7% for 2M HNO3 medium while extraction efficiency of uranium was still 95%. For tissue paper matrix, extraction efficiency for uranium with 0.2M DBEHA (in methanol) was 86% while only 11% thorium was extractable under same conditions. This fact could be exploited for separation of thorium and uranium.

Solvent extraction studies of uranium(VI) from phosphoric acid: Role of synergistic reagents in mixture with bis(2-ethylhexyl) phosphoric acid

The extraction of uranium(VI) from 5.3mol·L−1 H3PO4 (a typical concentration of wet phosphoric acid) with a series of neutral organosphosphorus synergistic reagents (0.125–0.250mol·L−1) used in mixture with 0.5mol·L−1 bis(2-ethylhexyl) phosphoric acid (D2EHPA) in Isane IP 185 (a 100% isoparaffinic aliphatic diluent) has been investigated. The series of synergistic reagents includes tri-n-butyl phosphate (TBP), di-n-butyl n-butyl phosphonate (DBBP), n-butyl di-n-butyl phosphinate (BDBP), tri-n-butyl phosphine oxide (TBPO), tri-n-hexyl phosphine oxide (THPO), tri-n-octyl phosphine oxide (TOPO), tri-n-decyl phosphine oxide (TDPO), di-n-hexyl n-decyl phosphine oxide (DHDPO), n-decyl di-n-hexyl phosphinate (DDHP) and di-n-hexyl octyl methoxy phosphine oxide (di-n-HMOPO). It appears that the presence of oxygen atoms at the vicinity of the phosphorus atom in the hydrophobic chains of the synergistic reagents, as in BDBP, DBBP and TBP, lowers significantly the extraction properties of uranium(VI) from phosphoric acid compared for instance to TBPO. Conversely, the increase of the hydrophobicity of the synergistic reagents by increasing the number of carbon atoms in their hydrophobic chains is responsible for an improvement of the extraction efficiency of uranium(VI). Among all the studied systems, the mixture of D2EHPA and di-n-HMOPO in Isane IP 185 leads to the best recovery of uranium(VI) from 5.3mol·L−1 H3PO4. A physicochemical model has been developed to simulate the extraction data and identify the equilibria involved in the recovery of uranium(VI) from 5.3mol·L−1 phosphoric acid by D2EHPA/di-n-HMOPO. A good agreement between experimental and calculated distribution coefficients of uranium(VI) is obtained by taking into account the following species in organic phase: H3PO4-S, (HL)2-S, (HL)5-S, (HL)2-(S)2 and UO2(HL2)2, UO2(HL2)2S, UO2L2S, where L denotes the monomeric deprotonated form of D2EHPA (HL) and S refers to di-n-HMOPO.

The Complexation of Calix[6]Arene Sulfoxide Derivative with Uranium

Calix[6]arene carbon chain alkyl sulfoxide derivative have been successfully synthesized. IR spectra confirmed the introduction of sulfoxide group on calix[6]arene. UV spectra indicated that calix[6]arene sulfoxide derivative has a high complexation of uranium. The coordination ratio between the calix[6]arene sulfoxide derivative with uranium is 3:2, which was determined by Job’s method. Extraction experiments showed that the extraction efficiency of uranium is able to achieve 73.8%, which suggested the potential application of calix[6]arene sulfoxide derivative as an excellent uranium extraction agent.

Uranium extraction enhancement form phosphoric acid by emulsion liquid membrane

This work is mainly concerned with the uranium extraction from phosphoric acid commercially produced by Abu Zaabal Fertilizers and Chemical Co., Egypt. This target would realize a dual purpose where the phosphate ore is considered as an alternative source of uranium besides eliminating its environmental contamination. The applied procedures are that of the new technology of emulsion liquid membrane. Authors have indeed pointed out that the variables explored still leave open to question the roles of stripping at the internal interface as well as the bulk transfer of uranium in the internal phase. For this purpose, two reducing agents are studied as additives to two organic solvent systems; namely the organophosphorous synergistic mixture of D2EHPA/TOPO as well as the tridodecyl amine. The relevant factors have first been optimized upon synthetic uraniferous phosphoric acid solution followed by the application upon the commercial acid after purification. These factors include the concentration of solvent system and the used emulsifier, acid concentration of the external and internal phases besides the nature and concentration of the reductant added to the internal phase. In addition, the permeation time as well as the oxidation state of the external phase was studied. All these factors have indeed been studied under different mixing speeds ranging from 300 up to 1,000 rpm. Ascorbic acid concentration, 1 % as an additive to the internal phosphoric acid phase (40 % P2O5) resulted in 95 % uranium extraction efficiency at the lower speed of 600 rpm.

Oxidative leaching kinetics of molybdenum-uranium ore in H2SO4 using H2O2 as an oxidizing agent

The processing of molybdenum-uranium ore in a sulfuric acid solution using hydrogen peroxide as an oxidant has been investigated. The leaching temperature, hydrogen peroxide concentration, sulfuric acid concentration, leaching time, particle size, liquid-to-solid ratio and agitation speed all have significant effects on the process. The optimum process operating parameters were: temperature: 95°C; H2O2 concentration: 0.5 M; sulfuric acid concentration: 2.5 M; time: 2 h; particle size: 74 μm, liquid-to-solid ratio: 14:1 and agitation speed: 600 rpm. Under these experimental conditions, the extraction efficiency of molybdenum was about 98.4%, and the uranium extraction efficiency was about 98.7%.

Solvent extraction of uranium from lean grade acidic sulfate leach liquor with alamine 336 reagent

This paper describes the solvent extraction studies carried out on an acidic low assay uranium bearing leach liquor generated during sulfuric acid leaching of a refractory uranium ore using alamine 336–isodecenol–kerosene reagent combine. The leach liquor has a U3O8 content of about 270 mg/L, free acidity 2.4 N H2SO4 and total dissolved solids concentration of 260 g/L. Process parameteric variation studies indicated strong influence of free acidity of the leach liquor, alamine 336 concentration and aqueous to organic phase ratio on the extraction efficiency of uranium. An extraction efficiency of about 95% was achieved when the free acidity of leach liquor was 1 N H2SO4 or lower, using 2% (v/v) alamine 336 at ambient temperature with an aqueous to organic phase ratio of 1:1. The loading capacity under these conditions was 1.2 g/L of U3O8. About 98% of the uranium values could be stripped from the loaded organic using 1 N NaCl in 0.2 N H2SO4. The solvent extraction studies aided in developing a suitable process flowsheet for treating refractory uranium ores which need high acidity during leaching and relatively lower acidity for purification by solvent extraction.

A density functional theory study of uranium(vi) nitrate monoamide complexes

Density functional theory calculations were performed on uranyl complexed with nitrate and monoamide ligands (L) [UO(2)(NO(3))(2)·2L]. The obtained results show that the complex stability is mainly governed by two factors: (i) the maximization of the polarizability of the coordinating ligand and (ii) the minimization of the steric hindrance effects. Furthermore, the electrostatic interaction between ligands and uranium(vi) was found to be a crucial parameter for the complex stability. These results pave the way to the definition of (quantitative) property/structure relationships for the in silico screening of monoamide ligands with improved extraction efficiency of uranium(vi) in nitrate acidic solution.