Selective Recovery Of Uranium Research Articles

Solubility of tris(2-methylbutyl) phosphate in supercritical carbon dioxide and its application for the recovery of uranium from U-Zr and U-Th aqueous solutions

The employment of supercritical fluid extraction (SFE) within the nuclear industry may reduce the environmental burden by reduction in solvent waste generation. In this perspective, a SFE based method was developed for selective extraction of uranium from U-Zr and U-Th solutions using tris-(2-methylbutyl) phosphate (T2MBP) as a ligand in supercritical carbon dioxide (SCCO2). Prior to SFE studies, the utilisation of T2MBP in SCCO2 was examined by carrying out solubility measurements using dynamic flow technique at (313−333) K and (10−20) MPa. T2MBP has sufficient solubility in SCCO2 and ranges from 2.55 × 10-2 mol·mol-1 to 8.95 × 10-2 mol·mol-1. The solubility increases with pressure and decreases with temperature, resulting in retrograde solubility behaviour. The experimental solubility data was successfully correlated using different density based semi-empirical equations. Based on the solubility data, selective recovery of uranium from U-Zr and U-Th solutions was demonstrated using SCCO2+T2MBP.

Hierarchical Self-Assembled Polyimide Microspheres Functionalized with Amidoxime Groups for Uranium-Containing Wastewater Remediation.

Through molecule self-assembly and subsequent surface functionalization, novel uranium adsorbent AO-OB hierarchical self-assembled polyimide microspheres (AO-OBHSPIMs) were obtained by introducing the amidoxime groups into hierarchical self-assembled polyimide microspheres for the efficient and selective recovery of uranium from wastewater. The results of Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), X-ray diffraction (XRD), and nitrogen adsorption-desorption isotherm showed that AO-OBHSPIMs were a semicrystalline polymer material with self-supporting hierarchical structure and low pore volume, and they were equipped with abundant amidoxime groups. Given the recognized selectivity of amidoxime groups and their hierarchical structure, AO-OBHSPIMs exhibited excellent selectivity to uranyl ions. Moreover, AO-OBHSPIMs exhibited good stability and recyclability and remarkable removal percentage within low-concentration solution (99.4%) and simulated uranium-containing wastewater (97.3%). AO-OBHSPIMs could be applied to fixed-bed column adsorption due to their large particle size and self-supporting hierarchical structure that can facilitate water flow. The in-depth discussion of the adsorption mechanism showed that the adsorption mainly depended on the combined action of electrostatic interactions and complexation, and the adsorption process was a spontaneous endothermic monolayer adsorption. In summary, AO-OBHSPIMs exhibited good application prospects in uranium-containing wastewater remediation.

Selective Recovery of Uranium from El-Sebaiya Phosphate Rocks Using Urea

Urea CO(NH2)2 is an effective selective lixiviant for uranium from phosphate raw material. Experiments were performed to determine the factors of uranium dissolution from El-Sebaiya phosphate ore. Under the optimized conditions, uranium is extracted almost completely without significant changes in the chemical composition of the phosphate ore. From the latter, highly pure uranium-free phosphoric acid can be prepared. Analysis of the kinetic data using shrinking core models shows that the uranium leaching from El-Sebaiya phosphate ore with urea is a process controlled by chemical reaction.

Control of pore chemistry in metal-organic frameworks for selective uranium extraction from seawater

Abstract Extracting uranium from seawater is of great importance for the sustainable development of nuclear energy. A central problem is to develop high-performance adsorbents to allow for efficient and selective recovery of uranium from seawater. Since the adsorption properties are strongly dependent on the functional groups and the architectures of the adsorbents, one option is to bond effectively functional groups onto high-surface-area materials. Here we report the first synthesis of amidoxime functionalized metal-organic frameworks MIL-101-OA, exhibiting excellent adsorption performance arising from the large surface areas of the metal-organic frameworks (MIL-101) and the high affinity of the amidoxime towards uranyl. The MIL-101-OA was synthesized via grafting of acrylonitrile onto the pores of MIL-101 followed by its conversion to amidoxime functionalities. The MIL-101-OA demonstrated excellent uranium adsorption capacities of 321 mg g −1 in simulated seawater and 4.6 mg g −1 in real seawater, which are competitive with the currently state-of-the-art uranium adsorbent.

Nanostructured Magnetic Sorbents for Selective Recovery of Uranium(VI) from Aqueous Solutions

Direct sol-gel, novel template, and additional high-temperature reduction procedures for preparing iron oxides and their composites, showing promise for selective sorption of dissolved U(VI) from aqueous media of various acidities, are described. The sorption activity of the materials was studied, the kinetic curves of the sorption were obtained, and the efficiency of the selective recovery of U(VI) from aqueous solutions with different pH values using the new sorbents was compared. The probable mechanism of the U(VI) sorption onto the sorbents studied was suggested on the basis of SEM, XPS, emf, and BET data. The quantitative sorption of U(VI) is determined to a greater extent by the composition of the sorbent solid phase, rather then by the specific surface area of the sorbents, which ranges from 0.1 to 47.3 m2 g−1 depending on the synthesis procedure. The crystalline Fe0 phase in the sorbents prepared using additional high-temperature reduction plays the key role in the U(VI) sorption by the reducing deposition mechanism. The saturation magnetization for this type of sorbents can reach 133–140 emu g−1, which is an additional advantage allowing magnetic separation of the spent sorbents from the treated solutions.

Selective recovery of uranium from Ca-Mg uranates by chlorination

A chlorination process is proposed for the uranium extraction and separation using CalciumMagnesium uranates such as starting reactants which were obtained by precipitation from uranyl nitrate solutions with calcium hydroxide. The study is based on thermodynamic and reaction analysis using chlorine gas as chlorination agent. The results showed that the chlorination reaction of Ca uranate is more feasible to occur than the Mg uranate. The products obtained after chlorination reactions were washed with deionized water to remove the chlorides produced and analyzed. The XRD patterns of the washed products indicated that the chlorination between 400 and 500 °C result in a single phase of calcium uranate (CaUO4) as reaction product. The formation of U3O8 and MgU3O10 was observed at temperatures between 600 °C and 700 °C for 8 hs. The optimal conditions to recover uranium were 3 l h−1 of chlorine and 10 hs of reaction at 700 °C being U3O8 the single uranium product obtained.

Development of a new solvent extraction process based on butyl-1-[N,N-bis(2-ethylhexyl)carbamoyl]nonyl phosphonic acid for the selective recovery of uranium(VI) from phosphoric acid

ABSTRACTThe promising new extractant molecule butyl-1-[N,N-bis(2-ethylhexyl)carbamoyl]nonyl phosphonic acid (DEHCNPB) was designed and used to develop a new solvent extraction process for the selective recovery of uranium from phosphoric acid. This bifunctional extracting molecule shows high affinity and selectivity for uranium(VI) versus iron(III) and the other elements present in phosphoric acid (Al, Ti, V, etc.). Batch equilibrium experiments were first carried out to determine the stoichiometries of the different complexes formed with uranium(VI) and iron(III) in organic phase and to optimize the different steps of the process at laboratory scale. These experimental data were then used to develop a chemical model to simulate uranium(VI) and iron(III) extraction from phosphoric acid, which was implemented in the PAREX simulation code. A flowsheet was calculated and tested in laboratory-scale mixer-settlers on a genuine phosphoric acid industrial solution. The continuous counter-current test was very successful and showed the possibility to recover more than 95% of uranium decontaminated from the main impurities. A Fe/U ratio of 0.03% was measured in the uranium product, which confirms the high potential of this new solvent for the further production of nuclear-grade uranium from phosphate ores.

Comparative dispersion-free solvent extraction of Uranium(VI) and Thorium(IV) by TBP and dialkyl amides using a hollow fiber contactor

Abstract Dispersion-free solvent extraction of U(VI) and Th(IV) from nitric acid medium was studied employing microporous hollow fiber membrane with several monoamide extractants, viz. N,N-di-2-ethylhexyl isobutyramide (D2EHiBA), N,N-dihexyl hexanamide (DHHA), N,N-dihexyl decanamide (DHDA) and N,N-dihexyl octanamide (DHOA), and the results were compared with those obtained with conventional TBP extractant. Effects of flow rate and feed metal ion concentration on the extraction rate were examined. The extraction was principally controlled by the distribution coefficient of the metal ions with the extractants. The studies were performed under different hydrodynamic conditions and the overall mass transfer coefficients of the extracting species were calculated and found to be independent of the flow rates. The overall extraction rates were governed by the viscosity and density of the organic phase. The separation factor between U(VI) and Th(IV) was excellent with branched chain monoamides, viz. D2EHiBA, followed by DHOA. The results indicated the selective recovery of Uranium in the presence of large concentrations of Thorium by monoamides in dispersion-free solvent extraction method. A mathematical model was employed for predicting the extraction behavior of metal ions, which gave an excellent match between the calculated and the experimental results.

Selective recovery of uranium from multicomponent salt systems on inorganic sorbents

The recovery of uranium from highly saline process solutions from extraction refining of uranium on Termoksid inorganic sorbents was studied under static and dynamic conditions. The isotherms of uranium sorption on these sorbents are described by the Freundlich equation. Termoksid inorganic sorbents proved to be efficient for exhaustive removal of uranium from process solutions from extraction refining of uranium.

Selective recovery of uranium and thorium ions from dilute aqueous solutions by animal biopolymers.

Selective actinide ion recovery from dilute, aqueous, multication waste streams is an important problem. The recovery of uranium (U) and thorium (Th) by various animal biopolymers was examined. Of four species of biopolymers tested, a high uptake of uranium and thorium was found in hen eggshell membrane (ESM) and silk proteins, with the maximum uranium and thorium recovery exceeding 98% and 79%, respectively. The uptake of U and Th was significantly affected by the pH of the solution. The optimum pH values were 6 and 3 for the uptake of U and Th, respectively. The effect of temperature differed with the metal. The uptake of U decreased with increasing temperature (30-50 degrees C), whereas the Th uptake increased with increasing temperature. Selective recovery of U and Th from dilute aqueous binary and multimetal solutions was also examined. ESM and silk proteins tested were effective and selective for removing each metal by controlling the pH and temperature of the solution. In multimetal systems, the order of sorption of ESM proteins was preferential: U > Cu > Cd > Mn > Pb > Th > Ni > Co > Zn at pH 6 and Th > U > Cu > Pb > Cd > Mn > Co > Ni = Zn at pH 3. These biopolymers appear to have potential for use in a commercial process for actinide recovery from actinide-containing wastewater.

Selective recovery of uranium(VI) from aqueous acid solutions using micellar ultrafiltration

Preconcentration and removal of uranyl ions from aqueous solutions were achieved by using micellar-enhanced ultrafiltration with complexing micellar aggregates composed of Triton X-100 and different hydrophobic ligands. Derivatives of 4-aminosalicylic acid (PAS) and of 1-(2-pyridylazo)-2-naphthol (PAN) having tuned alkyl chains were used as suitable chelating agents. The selective recovery of uranyl from acid samples containing also SrII and CdII is possible using the multi-step ultrafiltration approach with the PAN derivatives, whereas effective uranyl retention can be obtained with salicylates only in neutral to basic media.

Engineering aspects of ion exchange in hydrometallurgy

The first application of ion exchange to extractive hydrometallurgy is the use of a strong base anion exchange resin for selective recovery of uranium from sulfate leach liquors. The influence of the major variables on column operation is described, plant performance data are summarized, cost factors are enumerated, and the probable application of this operation to metals at least as valuable as copper is predicted.