Extraction Of Thorium Research Articles

Selective Extraction of Thorium from Rare Earth Elements Using Wrinkled Mesoporous Carbon.

Liquid fluoride thorium reactors have been considered as replacements for uranium-based nuclear reactors, having many economic and environmental advantages. The production of thorium is usually accompanied by the separation of thorium from rare earth elements since the major thorium production mineral, monazite, contains other rare earth elements. The conventional manufacturing process involves a liquid-liquid extraction with organic ligands. There is a need to develop solid state absorbents with good reusability for metal ion separation processes. Porous carbon is particularly interesting due to acid/base resistance. A new absorbent, surface-oxidized wrinkled mesoporous carbon (WMC-O), has been prepared for the selective extraction of thorium ions from rare earth ions. WMC-O shows high selectivity for thorium adsorption due to the 4+ oxidation state of thorium. The distribution coefficient ( Kd) of the WMC-O for thorium from all rare earth elements is 2 orders of magnitude larger than that of surface-oxidized activated carbon (13 × 104 vs 35 × 102 at pH 2.15). WMC-O also shows a high adsorption capacity for pure rare earth ions ( Kd > 3 × 105). These features make WMC-O a promising absorbent for thorium extraction and rare earth ion recovery.

Separation of Radioactive Elements from Ethiopian Kenticha Pegmatite Ore by Hydrometallurgical Methods

The leaching and extraction behavior of uranium and thorium from a high-grade Ethiopian pegmatite ore in a mixture of hydrofluoric acid and sulfuric acid has been investigated. The effects of variables such as the temperature, particle size, acid concentration, and leaching time were studied. The leaching efficiency of uranium increased with increasing temperature to 150°C, at which 96% removal of uranium was achieved. Particles in the size range of − 100 + 75 μm resulted in the highest leaching of uranium, while formation of a colloidal suspension was observed when using a fine particle size fraction (− 75 μm). The dissolution of uranium increased with increasing leaching time. No significant systematic dependence of the leachability of thorium on the above variables was observed. Optimum extraction of uranium and thorium using D2EHPA was obtained when using aqueous/organic phase volume ratio of 1:1, solvent concentration of 0.3 M, and contact time of 20 min.

Electrochemical behaviors and electrolytic separation of Th(IV) and Ce(III) in ThF4-CeF3-LiCl-KCl quaternary melt

Abstract The extraction and recycle of thorium is an essential step in the thorium-uranium closed fuel cycle designed for Thorium-based Molten Salt Reactor system (TMSR), and the separation of thorium from FPs especially lanthanides is a key issue in the thorium recovery. In this paper, the electrochemical behaviors of Th(IV) and Ce(III) on Mo electrode were studied by cyclic voltammetry (CV) and chronopotentiometry (CP) techniques at 773 K in ThF4(3 wt%)/CeF3(0.3 wt%)-LiCl-KCl ternary melt and CeF3(0.3 wt%)-ThF4(3 wt%)-LiCl-KCl quaternary melt, respectively. The reduction peaks of Th(IV)/Th(0) and Ce(III)/Ce(0) were at −1.83 V and −2.21 V (vs. Ag/AgCl) in the respective ternary melt, respectively, which were same with the values in the quaternary melt; however, the oxidation peaks in the CeF3-ThF4-LiCl-KCl melt shifted negatively about 0.1 V. Pulsed potential electrolysis of quaternary melt revealed that 98.9% of Th(IV) can be electrochemical separated from the melt with almost all cerium remaining in the melt, based on the inductively coupled plasma atomic emission spectrometer (ICP-AES) results.

Sulfuric acid baking and leaching of rare earth elements, thorium and phosphate from a monazite concentrate: Effect of bake temperature from 200 to 800 °C

Monazite, a rare earth and thorium bearing phosphate mineral, is one of the major minerals used for the production of rare earth elements. Although sulfuric acid baking is one of the main processing routes for extraction of rare earth elements from monazite, the chemistry involved is not well understood. In this study, a combination of chemical analysis and standard characterisation techniques (XRD, SEM-EDS, FT-IR and TG-DSC) was used to identify reaction processes occurring during the sulfuric acid baking of monazite between 200 and 800 °C. The effects of these reactions on the leachability of the rare earths, thorium and phosphate were also examined. It was observed that the sulfation reaction of monazite with acid was virtually complete after baking at 250 °C for 2 h, resulting in >90% solubilisation of rare earth elements, thorium and phosphate. After baking at 300 °C, a thorium phosphate type precipitate was formed during leaching, leading to a sharp decrease in extraction of thorium and phosphate, but the leaching of rare earth elements reached nearly 100%. The EDS and FT-IR analyses of this precipitate were indicative of a thorium pyrophosphate. As the bake temperature was further increased to 400–500 °C, extraction of thorium, phosphorus and the rare earth elements decreased due to formation of insoluble thorium-rare earth polyphosphates. The formation of these polyphosphates is thought to be related to dehydration of orthophosphoric acid produced in the initial reaction of monazite with sulfuric acid. Between 650 and 800 °C, monazite was partially re-formed, leading to a further decrease in rare earth extraction to 55%. The re-forming of monazite appeared to be due to a reaction between the thorium-rare earth polyphosphates and rare earth sulfates.

Supercritical fluid CO2 extraction of thorium from "black" sands of the Azov sea

Supercritical fluid CO2 extraction of thorium from "black" sands of the Azov sea

Decomposition of monazite concentrate in sulphuric acid

ABSTRACTA sulphuric acid bake-leach process was investigated for the extraction of rare earth elements (REEs), uranium, and thorium from a monazite concentrate. X-ray diffraction analysis showed the formation of water-soluble sulphates that readily dissolved during the water leach step. Nearly complete extraction of REEs, uranium, and thorium was achieved when the concentrate was baked at 250°C for 4 h with a sulphuric acid to concentrate (S/C) weight ratio of 4:1. At the 1:1 sulphuric acid to concentrate ratio ∼65% of REEs were leached while only ∼2–5% of uranium and thorium were extracted. Temperature (180–250°C) had little effect on the extraction of REEs, but greatly affected the extraction of thorium and uranium. In general, the extraction of thorium and uranium decreased with an increase in temperature. The effect of particle size (48–137 µm) was also tested and found to have little effect on the extraction of REEs. Acid consumption was calculated and found to increase with longer baking times (0.3–0.8 g acid/g concentrate). The major mineralogical phases formed because of the sulphation reaction included potassium cerium sulphate hydrate (2K2SO4·Ce(SO4)2·2H2O), lanthanum sulphate hydrate (La2(SO4)3·2H2O), sodium praseodymium sulphite hydrate (NaPr(SO3)2·2H2O), and neodymium sulphate hydrate (Nd2(SO4)3·5H2O), all of which were water-soluble.

ICP-MS DETERMINATION OF ULTRALOW CONTENTS OF URANIUM AND THORIUM IN ANTIQUE LEAD AFTER THEIR ISOLATION BY COUNTERCURRENT CHROMATOGRAPHY (LIQUID-CHROMATOGRAPHY WITH A FREE STATIONARY PHASE)

A methodical approach to reduction of the limit of uranium and thorium detection in antique lead is proposed. The approach includes separation of the elements in the extraction system based on tetraphenylmethylene diphosphine dioxide and their subsequent ICP-MS determination. The influence of phase contact time, medium acidity, concentration of the extractant on the extraction of uranium and thorium from nitric acid solutions was studied under conditions of batch extraction. It is shown that the matrix element (lead) is not recovered in the considered extraction system. We specified and optimized conditions for concentration of uranium and thorium and their elution with an aqueous solution of etidronic acid using countercurrent chromatography. The content of uranium and thorium in the sample of antique lead raised from the ocean floor are less than 10 –10 % wt.

Solvent Extraction and Separation of Thorium(IV) from Chloride Media by a Schiff Base

The Schiff base extractant, (E)-4-(2-hydroxyethylimino)pentan-2-one (AcEt), for thorium(IV) ions was characterized in methylene chloride in chloride media. Analyses of the conventional log10 D versus pH and versus log10 thorium ion concentration plots of the extraction equilibrium data reveal that the thorium(IV) ions were extracted as a complex that is characterized by having one ionizable hydrogen ion and a metal:ligand ratio of 1:1. The effects of contact time, A:O phase ratio and temperature on the extraction and stripping were studied. Extraction and stripping isotherms were constructed to determine the theoretical stages of the extraction and stripping processes. The thermodynamic parameters Gibbs energy (∆G°), enthalpy (∆H°) and entropy (∆S°) changes associated with the extraction processes were evaluated. Finally, the optimum parameters of solvent extraction were applied to a chloride leach liquor.

Solvent extraction of thorium (IV) from chloride solution using Schiff base and its application for spectrophotometric determination

Thorium (IV) was separated from chloride medium by solvent extraction with Schiff base chelating agent, (E)-4-(2-hydroxyphenyl imino) pentane-2-one (AcPh) that was prepared and characterized by FT-IR, 1H NMR, and elemental analysis. The extraction step was studied with regard to experimental parameters such as diluent type, pH, AcPh concentration, A:O ratio, contact time, temperature and interference of diverse ions on the recovery of thorium ion. The thorium (IV) was then back-extracted into aqueous media containing 0.5 M HNO3 to study the stripping conditions that were A:O ratio, contact time and room temperature. The optimum parameters were applied in the studied sample solution for the spectrophotometric determination at 540 nm with Thoron I. The accuracy of the developed method was tested with B2 standard reference material. Furthermore, the proposed method was successfully applied for the spectrophotometric determination of thorium ions in the geologic sample with good accuracy and precision.

Synthesis of UiO-66-OH zirconium metal-organic framework and its application for selective extraction and trace determination of thorium in water samples by spectrophotometry

In this study, a zirconium-based metal-organic framework (Zr-MOF), named UiO-66-OH, was synthesized by the solvo-thermal method and characterized by Fourier transform-infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM). This Zr-MOF was then employed as a sorbent for selective extraction and preconcentration of thorium ions after their complexation with 2‑(2,4‑dihydroxyphenyl)‑3,5,7‑trihydroxychromen‑4‑one (morin) from environmental water samples prior to its spectrophotometrical determination. The experimental parameters affecting extraction, such as pH of sample solution, amount of Zr-MOF, type and volume of eluting solvent, adsorption and desorption time, and concentration of complexing agent were evaluated and optimized. Under the optimized conditions, an enrichment factor of 250 was achieved. The limit of detection was calculated to be 0.35μg·L−1 with a linear range between 10 and 2000μg·L−1of thorium. The maximum sorption capacity of MOF toward thorium was found to be 47.5mg·g−1. The proposed procedure was successfully applied to the analysis of real water samples.

Utilization of thorium and U-ZrH1.6 fuels in various heterogeneous cores for TRIGA PUSPATI Reactor (RTP)

The use of thorium as nuclear fuel has been an appealing prospect for many years and will be great significance to nuclear power generation. There is an increasing need for more research on thorium as Malaysian government is currently active in the national Thorium Flagship Project, which was launched in 2014. The thorium project, which is still in phase 1, focuses on the research and development of the thorium extraction from mineral processing ore. Thus, the aim of the study is to investigate other alternative TRIGA PUSPATI Reactor (RTP) core designs that can fully utilize thorium. Currently, the RTP reactor has an average neutron flux of 2.797 x 1012 cm-2/s-1 and an effective multiplication factor, keff, of 1.001. The RTP core has a circular array core configuration with six circular rings. Each ring consists of 6, 12, 18, 24, 30 or 36 U-ZrH1.6 fuel rods. There are three main type of uranium weight, namely 8.5, 12 and 20 wt.%. For this research, uranium zirconium hydride (U-ZrH1.6) fuel rods in the RTP core were replaced by thorium (ThO2) fuel rods. Seven core configurations with different thorium fuel rods placements were modelled in a 2D structure and simulated using Monte Carlo n-particle (MCNPX) code. Results show that the highest initial criticality obtained is around 1.35101. Additionally there is a significant discrepancy between results from previous study and the work because of the large estimated leakage probability of approximately 21.7% and 2D model simplification.

Solid Phase Extraction of Thorium and Uranium and their Separation from Lanthanides using Humic Acid Silica Gel as a Low-Cost Adsorbent

Solid phase extraction and separation of thorium (Th), uranium (U) and lanthanides were achieved using a humic acid-modified silica gel (Si-HA). Adsorption capacity, effect of contact time, pH, and adsorbent dose were examined at room temperature. The maximum adsorbent capacities (pH = 3) for Th and U were 28.0 and 31.3 mg g-1, respectively. The isotherm parameters denoted that the adsorption was favorable and optimum conditions were attained within 90 min. The kinetic data conformed well to pseudo-second order and intra-particle diffusion models. The distribution coefficients of U, Th and lanthanides in EDTA, citric acid and nitric acid media signify the possible separation of each element from the others. The salinity did not significantly affect the ability of Si-HA to extract Th and U. The adsorbent stability and reusability were also assessed through four-adsorption-desorption cycles. The simplicity of the proposed separation method along with the stability of the adsorbent and high regeneration efficiency under acidic conditions demonstrated the merit of using Si-HA as a low-cost adsorbent.

A synergistic extraction strategy by Cyanex572 and Cyanex923 for Th(IV) separation

Abstract The synergistic extraction of thorium (Th) with a mixture of Cyanex572 and Cyanex923 in hydrochloric acid medium has been investigated in this paper. Cyanex572 is a novel commercial extractant produced by Cytec Industries Inc. Up to now, no synergistic extraction concerning Cyanex572 has been reported. In this study, a significant synergistic effect was indicated by the combination of Cyanex572 and Cyanex923 for Th(IV). At the acidity of 0.1 mol/L, the largest synergistic enhancement coefficient from equal mole fraction of Cyanex572 and Cyanex923 reached 5.63. Extraction mechanism of mixed Cyanex572 and Cyanex923 for Th(IV) was proposed by slope analysis method and IR spectra, the composition of extracted complexes was determined as ThCl 2 (HL 2 ) 2 B. The synergistic extraction system has revealed a potential application value in the separation of Th(IV) from leaching solution of rare earth (RE) radioactive waste residue.

The novel extractants, bis-triamides: Synthesis and selective extraction of thorium(IV) from nitric acid media

Abstract Four novel soft-hard donor bis-triamide extractants were rationally designed, synthesized and characterized for the highly efficient extraction of Th(IV) from nitric acid medium in different diluents. The results indicate that L2 and L3 exhibit higher distribution ratio values for thorium than those of L1 and L4 in nitrobenzene. Further studies including the effects of acidity, the concentration of extractant, the determination of extraction capacity of Th(IV) and the temperature on the distribution ratios of Th(IV) were limited to L2 and L3 . The results reveal that Th(IV) is extracted into the organic phase as the extracted complex with a metal/extractant ratio of 1: 2. The maximum extraction capacity of Th(IV) with L2 and L3 is 995 mg/L and 1085 mg/L, respectively. The thermodynamic parameters (Δ H , Δ S and Δ G ) associated with the extraction process were determined, and the results show that the process is endothermic and spontaneous at room temperature. Moreover, L3 shows the highest selectivity for Th(IV) over U(VI), Am(III), Eu(III) and Sr(II) in 0.1–3.0 M HNO 3 solution. Stripping experiments indicate that the best stripping performance for Th(IV) is achieved by using 2.0 M Na 2 CO 3 as a stripping agent and its stripping percentages can reach 99% by the third stage.

Comparative study on thorium (İv) sorption onto sodic bentonite and magnetic bentonite

In this paper, the liquid-solid extraction of Thorium (IV) is made by Sodic bentonite and Magnetic bentonite. Magnetic adsorbent can be quickly separated from a medium by a simple magnetic process, in view of these properties; some parameters were studied to assess the performance of maghemite nanocomposite clay for the removal of Thorium ions. The operating variables studied are initial La(III) concentration, pH, ionic strength, temperature and contact time. The time needed for magnetic bentonite to adsorb the maximum of Th (IV) is 45 minutes and 60 minutes for sodic bentonite. For magnetic bentonite, optimal extraction yield was achieved in a initial pH equal at 6.2 and for sodic bentonite, the variation of initial pH has no influence on the extraction yield. The sorption capacities of sodic bentonite and magnetic bentonite are 41.24 and 31.34 mg.g -1 respectively. Adsorption equilibrium data were calculated for Langmuir and Freundlich isotherms. It was found that the sorption of Th (IV) on sodic and magnetic bentonite was better suited to the Langmuir adsorption model. Thermodynamics data leads to endothermic and spontaneous process for magnetic bentonite and exothermal for sodic bentonite. The quantitative elution study of Thorium can be realized with acetic acid for sodic bentonite and sulfuric acid for magnetic bentonite.

Flotation-assisted homogeneous liquid–liquid microextraction for determination of thorium in water samples by inductively coupled plasma–mass spectrometry and Box–Behnken design

ABSTRACTA fast, simple, and efficient method for extraction, preconcentration, and determination of thorium in water samples with acceptable recoveries based on flotation-assisted homogenous liquid–liquid microextraction combined with inductively coupled plasma–mass spectrometry (ICP-MS) is presented. Various parameters affecting the extraction efficiency were optimized by Box–Behnken design. Under the optimum conditions (concentration of dimethyl vinyl phosphonate = 2.4 × 10–4 mol/L, pH = 6.5, n-heptane = 150 μL, and acetonitrile = 0.5 mL), the calibration graph was linear in the range of 10.0–400.0 ng/L for thorium. The limit of detection of this method was 2.62 ng/L, and the enrichment factor was estimated to be 136 for thorium.

Alkali pug bake process for the decomposition of monazite concentrates

An alkali pug bake-leach process was studied for the decomposition of monazite and extraction of rare earth elements (REEs), uranium, and thorium. Under the conditions studied, 4h bake time and 210°C with an alkali to concentrate ratio (A/C) of 4:1 allowed for relatively high REEs extraction while maintaining relatively low thorium and uranium extraction, which may allow for at least partial separation of REEs from thorium and uranium. At this level, and with an average particle size of 81µm, more than 90% of REEs were extracted, uranium extraction dropped to ∼38% by partly reporting to the water leach solution, and thorium extraction was consistently low at ∼25%. Baking temperature (180–250°C) was found to have a pronounced effect on the extraction of REEs, uranium, and thorium. The maximum extraction of REEs was achieved during the 210°C, 3h bake time test. Thorium extraction was greater than 90% in the 2h bake time at 210°C, then dropped drastically to 50% or less for the 3 and 4h bake times. Uranium extraction preferred the 250°C level, but remained fairly low for the vast majority of the levels tested. The effect of particle size (48–137μm) was studied at 210°C and was found to have some effect on the extraction in the 1 and 2h tests. However, in the 3 and 4h tests, extractions were of similar magnitude for all three particle sizes studied. Thorium extraction peaked during the 2h test and then dropped in 3 and 4h tests. Alkali consumption was calculated and found to increase with increasing temperature and decreasing particle size (0.01–0.22g alkali/g concentrate). Alkali consumption was increased with increasing extraction. The drop off in extraction is attributed to the dehydration of the hydroxides produced and the formation of insoluble phosphate phases.

Synergistic effect of tri-n-butyl phosphate (TBP) or tri-n-octyl phosphine oxide (TOPO) with didodecylphosphoric acid (HDDPA) on extraction of uranium(VI) and thorium(IV) ions

Importance of removal of radioactive elements from wastewater was the motivation behind this work. Synergistic solvent extraction of U(VI) and Th(IV) ions from perchlorate solution using didodecylphosphoric acid (HDDPA) incorporated with tri-n-butyl phosphate (TBP) or tri-n-octylphosphine oxide (TOPO) as a synergists have been studied for the first time. The effects of HDDPA concentration, synergist’s concentration, pH values and temperature on the extraction process have been studied. The thermodynamic parameters of the extraction process for these ions were calculated. It was found that the synergistic contribution of TOPO is higher than TBP in the extraction of Th(IV) and U(VI).

Extraction and recovery of cerium(IV) and thorium(IV) from sulphate medium by an α-aminophosphonate extractant

In the present work, a novel α-aminophosphonate extractant (Cextrant 230) was synthesized for the extraction and recovery of cerium and thorium from sulphate medium. The introduction of amine group into the phosphate molecule would enhance the extraction of Ce(IV) and Th(IV). The effects of extractant concentration, H2SO4 concentration and temperature on the metal extraction were investigated in detail. It was found that the extraction of Ce(IV), Th(IV) and REs (La, Gd, Yb) in sulphate medium decreased in the following order: Ce(IV)>Th(IV)>REs(III). A solvent extraction process to extract and recover cerium and thorium from bastnasite leaching was proposed, in which the purities of cerium and thorium products reached 99.9% and 99% with yield of 92% and 98%, respectively.

Hydrometallurgical digestion and leaching of Iranian monazite concentrate containing rare earth elements Th, Ce, La and Nd

Rare earth elements (REEs) have an ever-increasing variety of applications in modern technology. In the present work, the possibility of extraction of rare earth elements cerium (Ce), lanthanum (La), neodymium (Nd) and thorium (Th) from a monazite concentrate containing 25% rare earth elements' oxide was investigated. In this regard, the acidic digestion and leaching step, and their effective parameters were studied in detail using design of experiment (DOE) which hadn't been investigated before. The optimum conditions for the performed experiments in acidic digestion step were: temperature of 225°C, time of 3.5h and sulfuric acid to concentrate weight ratio (L/S) of 2.5. Using these conditions, the recovery of 92.34%, 91.44%, 92.1% and 88.94% were obtained for cerium, lanthanum, neodymium and thorium, respectively. In leaching step, the optimum conditions were: temperature of 75°C, time of 15h and water to digested mass weight ratio of 7.5. Using these conditions, recovery of 88.47%, 89.45%, 87.35% and 82.19% were obtained for rare earth elements cerium, lanthanum, neodymium and thorium, respectively. In precipitation step, rare earths' oxalates were precipitated from the leach liquor using oxalic acid. Then, the precipitate was calcined in a furnace at 800°C for 1h and finally, a mixture of rare earth elements' oxides with a purity of about 84% was obtained.