Synergistic extraction of uranium from acidic sulfate leach liquor using D2EHPA mixed with TOPO

Uranium extraction from sulfate leach liquor acid by D₂EHPA and TOPO mixture in kerosene was investigated. The effect of different factors affecting the extraction mechanism such as sulfate leach liquor acid, D₂EHPA and TOPO concentrations and temperature have been studied. The mathematical treatment for the obtained date suggested that the composition of synergistic extraction species is (UO₂(D)₂T). The logarithm of the apparent equilibrium constant, log Kex, of synergistic extraction reaction has been evaluated, to be 3.35 ± 0.1. The effect of temperature on extraction process was investigated and the apparent values of the thermodynamics parameters (?H, ?G and ?S) were 38.2 kJ/mol, ?19.1 kJ/mol and 192.5 J/mol respectively.     

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?Cisodecenol?Ckerosene 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 Study on the extraction of uranium(VI) from sulphate leach liquor using LIX63

The sulphate leach liquor obtained from the sulphuric acid leaching process of Egyptian monazite was treated using solvent extraction to recover U(VI) by LIX63. The influence of various basic variables such as pH, concentration of LIX63, temperature, different stripping agent, phase ratio and diluents was examined. Using 10% LIX63 with the aqueous solution at equilibrium pH 5.5 and a phase ratio A/O?=?1/1, a four-stage McCabe-Thiele plot was constructed, which showed 85.57% of U(VI) extraction. The thermodynamic data showed that the extraction process is exothermic with enthalpy change ΔH?=???43.866?kJ/mol, the stripping of U(VI) was quantitative using 4?M HNO₃. The stable complex UO₂(HSO₄)R_org formed during extraction which supports the cation exchange mechanism was confirmed by FTIR spectral analysis. Uranium cake was finally obtained from the strip solution by the addition of hydrogen peroxide and ammonium hydroxide as precipitating agents, and a workable flowsheet was then formulated.     

Uranium(VI) recovery from acidic leach liquor using manganese oxide coated zeolite (MOCZ) modified with amine

Journal of Radioanalytical and Nuclear Chemistry - Manganese oxide coated zeolite modified with trioctyl amine (MOCZ/TOA) was tested for adsorption of uranium. Different experiments were performed...     

Automatic analysis of uranium-bearing extracts in amine solvent extraction plants processing sulfate leach liquors

Summary Instrumentation based on continuous segmented flow analysis is suggested for the control of uranium loading in the amine phase of solvent extraction plants processing sulfate leach liquors. It can be installed with relatively little capital outlay and operational costs are expected to be low. The uranium(VI) in up to 60 samples of extract (0.1 to 5 g l^–1 U) per hour can be determined. Application of spectrophotometry to the analysis of various process streams is discussed and it is concluded that it compares favourably in several important respects with the use of alternative techniques.

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Automatische Analyse uranhaltiger Extrakte bei der Verarbeitung aminhaltiger Sulfatlaugen

Zusammenfassung Die vorgeschlagene Kontrolle der Uranbelastung beruht auf der Durchflußanalyse mit kontinuierlicher Segmentierung. Der Aufwand ist relativ gering und auch die Betriebskosten sind niedrig. Uran(VI) kann in bis zu 60 Proben je Stunde (0,1–5 g/l U) bestimmt werden. Die Anwendung der Spektralphotometrie für die Analyse verschiedener Prozeßströme wird diskutiert. In mehrfacher Hinsicht ist das Verfahren mit anderen Methoden gut vergleichbar.

     

Hydration of tri-n-hexyl amine hydrochloride,tri-n-octyl amine hydrochloride,tri-n-decyl amine hydrochloride and tri-n-dodecyl amine hydrochloride benzene solutions

Isopiestic equilibrations of THxA·HCl, TOA·HCl, TDA·HCl and TLA·HCl benzene solutions have been made in the concentration range from 0·02 to 0·13 mole/kg at different water activities and 25°C. The mean hydration number of the chloride ion at unit water activity was found to be 1·024±0·015 for the systems investigated. To determine the effect of water activity on the amine salt activity the results were treated on the basis of the Gibbs-Duhem equation and a simple linear relation obtained between salt and water activities. IR spectrophotometric measurements were performed to identify the nature of the hydrated species.     

Experimental study on the uranium(VI) extraction rate and droplet mass transfer coefficients from a sulfate leach liquor medium with Alamine 336 in a single drop column

Journal of Radioanalytical and Nuclear Chemistry - The mass transfer coefficient and the extraction degree of uranium was investigated from a leach liquor by Alamine 336 in a single drop column....     

Study of scandium and thorium sorption from uranium leach liquors

Scandium and thorium sorption from simulated uranium leach liquors by phosphorous containing ion exchange resins was studied. Increase of thorium concentration resulted in a decrease of scandium sorption by 26–65%. Tulsion CH 93 resin was chosen for Sc separation from uranium leach liquors. It was shown that 180 g L^?1 Na₂CO₃ allowed for elution 94.1% of Sc and 98.9% of Th in dynamic conditions. Using (NH₄)₂SO₄ (50 g L^?1) + ACBM (180 g L^?1) mixture for primary Sc/Th separation at the resin/eluent ratio of 1:5 resulted in thorium desorption degree as high as 66–69%, whereas scandium loss did not exceed 10%.     

Removal of uranium from aqueous solution using montmorillonite-supported nanoscale zero-valent iron

Montmorillonite-supported nanoscale zero-valent iron (M-nZVI) was synthesized by sodium borohydride reduction and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and field emission scanning electron microscopy (FE-SEM). The interaction of uranium with M-nZVI was studied using batch technique under different experimental conditions such as pH, ionic strength, initial U(VI) concentration, solid-to-liquid ration (m/V), and temperature. The presence of montmorillonite decreased the aggregation while increased the specific surface area (SSA) of the iron nanoparticles. The SSA for as-synthesized M-nZVI was 91.42 m²/g, higher than 26.60 and 10.23 m²/g for nZVI and montmorillonite, respectively. The removal efficiency of U(VI) using M-nZVI was significantly affected by the pH of the aqueous solution, whereas it was slightly affected by ionic strength and temperature. The isoelectric point of M-nZVI was at pH 5.6; however the results indicated that the optimum removal efficiency of U(VI) using M-nZVI was achieved at a pH range 3.0–5.0. The experiments with aqueous solution containing 100 μg/L of U(VI) showed that the removal efficiency of the as-synthesized M-nZVI was about 978 μg/g at pH 3.0. These results show that M-nZVI has a potential as a novel material for removing U(VI) from aqueous solution.     

Removal of unsaturated aliphatic carboxylic acid from aqueous effluent using quaternary amine

Maleic acid, present in the effluent from organic intermediate producing industries, is an industrially important raw material. Its use in manufacture of alkyd and polyester resins, surface coatings, lubricant additives, plasticizers, co-polymers and agricultural chemicals, makes it necessary to explore for best possible techniques to recover it from aqueous solutions. The present work investigates the recovery of maleic acid from aqueous solution at ambient temperature. N–Methyl–n, n–dioctyloctan–1–ammonium chloride, (commercially known as Aliquat 336) is used as an extractant with three different diluents, belonging to different chemical classes: an aromatic hydrocarbon, a ketone, and an acetate. The chemical extraction results are reported in the terms of distribution coefficient, degree of extraction, and loading ratios. The results were modeled by mass action equilibria model as well as differential evolution technique. Differential evolution algorithm has been prepared. The model and experimental observations were compared and fairly good agreement was observed.     

Radiochemical characterization and decontamination of rare-earth-element concentrate recovered from uranium leach liquors

Journal of Radioanalytical and Nuclear Chemistry - The paper deals with two rare earth elements (REE) concentrates recovered from uranium leach liquors after sorption separation of uranium....     

Removal of uranium(VI) from aqueous solution using sponge iron

Direct reduced iron (DRI), also called sponge iron, was used for the removal of U(VI) from aqueous solution. Batch experiments were conducted to evaluate the effect of various factors including contact time, solution pH, DRI dosage and initial uranium concentration on this removal process. The result suggested that U(VI) can be rapidly removed by DRI and this removal process followed an apparent first-order reaction kinetics. The optimum pH for uranium removal was between 2.0 and 4.0. Whether U(VI) can be fully removed was influenced by the molar ratio of DRI to U(VI) in solution. The aqueous U(VI) can be removed completely when this ratio was more than ca. 1,000. The U(VI) removal capacities of DRI decreased with increasing DRI dosages at a constant concentration of U(VI), but increased almost linearly with increasing initial U(VI) concentrations at a fixed dosage of DRI. The maximum U(VI) removal capacity was 5.71 mg/g DRI. Finally, the possible mechanism of U(VI) removal by DRI was also discussed. The XPS and XRD analysis showed that U(VI) was deposited as UO₃ onto DRI surface, indicating that U(VI) can be removed without reduction.     

Uranium(VI) recovery from its leach liquor using zirconium molybdophosphate composite: kinetic,equilibrium and thermodynamic studies

Journal of Radioanalytical and Nuclear Chemistry - A zirconium molybdophosphate composite was designed for the selective recovery of uranium ions. The synthesized composite was well-characterized...     

Salt evaporation behaviors of uranium deposits from an electrorefiner

From an electrorefining process, uranium deposits were recovered at the solid cathode of an electrorefining system. The uranium deposits from the electrorefiner contained about 30–40 wt% salts. In order to recover pure uranium and transform it into metal ingots, these salts have to be removed. A salt distiller was adapted for a salt evaporation. A batch operation for the salt removal was carried out by a heating and a vacuum evaporation. The operational conditions were a 700–1,000 °C hold temperature and less than a 1 Torr under Argon atmosphere, respectively. The behaviors of the salt evaporations were investigated by focusing on the effects of the pressure and the holding temperature for the salt distillation. The removal efficiencies of the salts were obtained with regard to the operational conditions. The experimental results of the salt evaporations were evaluated by using the Hertz-Langmuir relation. The effective evaporation coefficients of this relation were obtained with regards to the vacuum pressures and the hold temperatures. The higher the vacuum pressure and the higher the holding temperature were, the higher the removal efficiencies of the salts were.