Thorium Phosphate Research Articles

Investigation of the Thermal Properties of Alkali Metal Thorium Phosphates and Their Application for the Sorption of Uranyl Ion from Acidic Medium

AbstractThermo physical properties of potassium, rubidium and cesium thorium phosphate compounds were investigated. All compounds were synthesized by conventional solid state method. Formation of orthorhombic AMThP3O10, tetragonal AM2Th(PO4)2 and monoclinic AMTh2(PO4)3; [AM=K, Rb and Cs] was confirmed using Powder X‐ray diffraction (XRD) technique. Structural study of CsThP3O10 was carried out for the first time from Rietveld refinement of XRD data. Thermal stability of all compounds was established using Thermogravimetric analysis (TGA) technique. When heated at 1673 K for 30 h in air, all the compounds decompose to ThO2. High temperature X‐ray diffraction (HT‐XRD) data of the compounds, synthesized during present study, were collected in an inert atmosphere from ambient to 973 K and their thermal expansion coefficients were calculated. These compounds show positive thermal expansion up to 973 K. Molar heat capacities for all phosphates were measured between 300–863 K using Differential Scanning Calorimeter. Alkali metal thorium phosphates, AMThP3O10 and AMTh2(PO4)3, showed efficient uptake of uranyl ion from aqueous acidic medium predominantly following Langmuir isotherm and Webber Morris intra particle diffusion kinetics.

Development of a recovery process of thorium and possible separation of rare earths from Korean monazite

ABSTRACT Systematic studies were carried out to leach out rare earths and recover thorium from Korean monazite. Monazite was processed with acid baking process (sulfation) where rare earth elements (REEs) and thorium phosphates were transformed to water-soluble sulfates. Various experimental factors such as temperature, H2SO4/monazite concentrate ratio and time were studied to get optimized sulfation system. Near to 88% of leaching of REEs and Th was performed after sulfation followed by water leaching. Moreover, by using 0.1 mol/L of primary amine Primene JM-T (tri-alkyl-methylamine), thorium was separated (more than 95%) from the light rare earth elements present in the leach liquor. Subsequently, rare earth elements were separated by solvent extraction technique using Cyanex 572 as an extractant at different pH conditions. High separation coefficients for different rare earths were obtained with Cyanex 572, while Primene JM-T resulted in the complete separation of the thorium from the leach liquor.

COM-1 and Hongcheon: New monazite reference materials for the microspot analysis of oxygen isotopic composition

BackgroundMonazite, a moderately common light rare earth element (LREE) and thorium phosphate mineral, has chemical, age, and isotopic characteristics that are useful in the investigation of the origin and evolution of crustal melts and fluid-rock interactions. Multiple stages of growth and partial recrystallization commonly observed in monazite inevitably require microspot chemical and isotopic analyses, for which well-characterized reference materials are essential to correct instrumental biases. In this study, we introduce new monazite reference materials COM-1 and Hongcheon for the use in the microspot analysis of oxygen isotopic composition.FindingsCOM-1 and Hongcheon were derived from a late Mesoproterozoic (~ 1080 Ma) pegmatite dyke in Colorado, USA, and a Late Triassic (~ 230 Ma) carbonatite-hosted REE ore in central Korea, respectively. The COM-1 monazite has much higher levels of Th (8.77 ± 0.56 wt.%), Si (0.82 ± 0.07 wt.%) and lower REE contents (total REE = 49.5 ± 1.2 wt.%) than does the Hongcheon monazite (Th, 0.23 ± 0.11 wt.%; Si, < 0.1 wt.%; total REE, 59.9 ± 0.7 wt.%). Their oxygen isotopic compositions (δ18OVSMOW) were determined by gas-source mass spectrometry with laser fluorination (COM-1, 6.67 ± 0.08‰; Hongcheon-1, 6.60 ± 0.02‰; Hongcheon-2, 6.08 ± 0.07‰). Oxygen isotope measurements performed by a Cameca IMS1300-HR3 ion probe showed a strong linear dependence (R2 = 0.99) of the instrumental mass fractionation on the total REE contents.ConclusionsWe characterized chemical and oxygen isotopic compositions of COM-1 and Hongcheon monazites. Their internal homogeneity in oxygen isotopic composition and chemical difference provide an efficient tool for calibrating instrumental mass fractionation occurring during secondary ion mass spectrometry analyses.

Implications of Magnetic Properties in the Concentration and Distribution of REEs in Beach Placer Monazites: A Case Study from Chhatrapur Coast, Odisha

Abstract The concentration of monazite, a rare earth and thorium phosphate, in the heavy mineral-bearing sands of Chhatrapur coast varies from 0.09 to 0.16%. Under the microscope, monazite displays color variation from colorless to various shades of yellow, green and brown. The color variation is further reflected in the chemistry of individual grains. Such monazites of distinct colors and different chemistry also show variation in their paramagnetic properties. Representative detrital monazites separated under varied magnetic field strength were analysed for their rare earth elements, Th and U content. The electron probe micro analysis (EPMA) data indicate that monazites separated under low magnetic field strength (separated at 0.80 amps) are characterized by their higher Nd, Sm, HREE, Y and U as well as low Th content, whereas those separated at 1.10 amps contain low Nd, Sm, HREE with negligible Y and U content as well as higher Th content. The wider variation in the concentration of different rare earths in varied magnetic field strength is a function of varied magnetic susceptibility of individual elements. Hence, the physical method for separation of monazite using magnetic properties may facilitate to segregate the monazites of a particular chemical composition with respect to their constituent elements like U, Th and rare earths based on their magnetic properties.

Crystalline phosphates for HLW immobilization - composition, structure, properties and production of ceramics. Spark Plasma Sintering as a promising sintering technology

Available publications on crystalline materials used to immobilize HLW and actinides have been analyzed. Select compounds and solid solutions covered in this paper are phosphates of the following structural families: monazite, xenotime, kosnarite (NZP),apatite and britholite, langbeinite, whitlockite and thorium phosphate diphosphate (TPD). These materials have been shown to be fit for “nature-like” disposal (except TPD), they have a wide spectrum of isomorphic substitutions of cations and/or anions, and high heat, chemical, and irradiation stability. They can be also used in geoenvironmental engineering. The studies taken into consideration follow the materials science approach that rests on the “composition – structure – synthesis – property” basis. The analyzed papers describe materials synthesized using Spark Plasma Sintering, a process that results in rapid formation of virtually poreless ceramics and improves environmental safety both at stage of HLW immobilization and during long-term storage.

Studies on Sodium Lauryl Sulphate-supported Thorium (IV) Phosphate: A New Surfactant-supported Cation Exchange Resin, Useful in Water Purification

Background: With the increasing population and decreased quality of drinking water, new materials and methods for the purification of water need to be developed. This study aims to present a solution from pollution by proposing the synthesis method of sodium lauryl sulphate (SLS)-supported thorium (IV) phosphate (ThP), its characterisation and disquisition of analytical applications by executing dual separations of calcium. Methods: SLS ThP was synthesised by the sol-gel method. The synthesised exchanger was characterised by physicochemical methods, such as powdered X-ray diffraction, scanning electron microscopy, thermo-gravimetric-differential thermal analysis, EDAX and Fourier transform-infrared study. Also, its competency towards the ion exchange processes and in analytical chemistry was verified. Results: The prominent characteristic of SLS-supported ThP was its high ion exchange capacity for sodium ions (3.10 meq/g), which is almost 2.5 times more than the exchange capacity of ThP, i.e., 1.3 meq/g. The material resulted in a fibrous sheet that is thermally and mechanically stable but poorly crystalline and shows selectivity towards Ca2+ and Hg2+ ions. Conclusion: The synthesised cation exchange material is thermally stable, showing drastically high exchange capacity and selectivity towards Hg2+ and Ca2+ metal ions, which might be because of the use of an anionic surfactant, SLS, while the synthesis of ThP plays a key role in enhancing the exchange capacity and adsorption of specific metals. Therefore, based on the results obtained, the above-said materials have applications in water purification processes and environmental pollution control where removal of Hg2+ and Ca2+ is essential.

Synthesis and structure of triple thorium phosphates with monazite structure

Three monazites MIILaTh(PO4)3 (MII = Ca, Sr, Cd) have been studied both computationally and experimentally to determine the influence of the MII cation nature on monazite crystal structure and characteristics important for their use as matrix forms for immobilizing radioactive waste. Their crystal structures have been refined by the Rietveld method. Functional composition has been confirmed by IR spectroscopy. Thermal stability has been tested by DTA-TG.

Frontier looking of rare-earth processed residue as sustainable thorium resources: An Insight into chemical composition and separation of thorium

Rare-earth (RE) extraction activities in Malaysia produce an average of 75000 tonnes of Water Leach Purification (WLP) residue containing an estimated 106 tonnes of thorium that leads to negative perception and concern among the public especially related to the environmental and radiological aspects. The main challenge to separate thorium from the WLP residues is the formation of insoluble thorium pyrophosphate (ThP2O7) due to the treatment process during rare-earth extraction. Therefore, the objectives of this study are to verify the thorium composition in WLP residue as well as to investigate the possibility of separating thorium from WLP. The characterizations using FTIR, SEM-EDS, XRD, and XPS verified the presence of ThP2O7 along with other thorium phosphate compounds (Th(PO3)4) and (Th3(PO4)4) in WLP residue. The digestion study using sulphuric acid (H2SO4) at various molarity ranging from 3 to 18 mol/L showed that thorium in WLP can be dissolved in acid. The dissolution of thorium up to 50% was achieved at 6 mol/L H2SO4 and further increase to 90% with the increase of acid molarity at 150 °C within an hour of the leaching time. This research showed promising findings on the separating thorium from WLP residue through the acid digestion process that might open up the possibility of recycling rare-earth residue as sustainable thorium resources.

Studies on polyoxyethylene octyl phenyl ether supported thorium(IV) phosphates: a new cation exchange material

A new surfactant supported cation exchanger and adsorbent named, polyoxyethylene octyl phenyl ether supported thorium(IV) phosphate (TX-100ThP) has been reported along with its synthesis, physico-chemical characterization such as scanning electron microscopy, X-ray diffraction, thermogravimetric analysis–differential thermal analysis and Fourier transform infra-red study. Following the characterization, the formed product has been tested for its efficiency in ion exchange chemistry and in analytical chemistry. For the testing, adsorption of alkaline earths—Mg2+, Ca2+, Sr2+ and Ba2+ and transition metal ions such as Fe3+, Mn2+, Ni2+, Cd2+, Co2+, Cu2+, Hg2+ and Pb2+ have been explored in different acidic media and the results revealed the selectivity of synthesized material towards Hg2+ ions. On that basis, the material has been used to treat the binary laboratory-made samples, exploring the environmental importance of the cation exchanger in material science.

Ceramic Mineral Waste-Forms for Nuclear Waste Immobilization.

Crystalline ceramics are intensively investigated as effective materials in various nuclear energy applications, such as inert matrix and accident tolerant fuels and nuclear waste immobilization. This paper presents an analysis of the current status of work in this field of material sciences. We have considered inorganic materials characterized by different structures, including simple oxides with fluorite structure, complex oxides (pyrochlore, murataite, zirconolite, perovskite, hollandite, garnet, crichtonite, freudenbergite, and P-pollucite), simple silicates (zircon/thorite/coffinite, titanite (sphen), britholite), framework silicates (zeolite, pollucite, nepheline /leucite, sodalite, cancrinite, micas structures), phosphates (monazite, xenotime, apatite, kosnarite (NZP), langbeinite, thorium phosphate diphosphate, struvite, meta-ankoleite), and aluminates with a magnetoplumbite structure. These materials can contain in their composition various cations in different combinations and ratios: Li–Cs, Tl, Ag, Be–Ba, Pb, Mn, Co, Ni, Cu, Cd, B, Al, Fe, Ga, Sc, Cr, V, Sb, Nb, Ta, La, Ce, rare-earth elements (REEs), Si, Ti, Zr, Hf, Sn, Bi, Nb, Th, U, Np, Pu, Am and Cm. They can be prepared in the form of powders, including nano-powders, as well as in form of monolith (bulk) ceramics. To produce ceramics, cold pressing and sintering (frittage), hot pressing, hot isostatic pressing and spark plasma sintering (SPS) can be used. The SPS method is now considered as one of most promising in applications with actual radioactive substances, enabling a densification of up to 98–99.9% to be achieved in a few minutes. Characteristics of the structures obtained (e.g., syngony, unit cell parameters, drawings) are described based upon an analysis of 462 publications.

Crystallization Pathways of Cerium(IV) Phosphates Under Hydrothermal Conditions: A Search for New Phases with a Tunnel Structure

Hydrothermal crystallization pathways of amorphous ceric phosphate gels were found to be determined by the ammonia concentration in a reaction medium. This allows for highly selective hydrothermal synthesis of various finely crystalline ceric phosphates, including Ce(PO4)(HPO4)0.5(H2O)0.5, (NH4)2Ce(PO4)2(H2O), and previously unknown NH4Ce2(PO4)3. The structure of the latter compound was solved from powder X‐ray diffraction data. It appeared to be isostructural to ammonium thorium phosphate, NH4Th2(PO4)3; in this crystal structure, large channels (5.07 × 3.79 Å) located along the c‐axis are occupied by NH4+ ions.

Characterization of Malaysian Monazite Concentrate for The Recovery of Thorium Dioxide

Malaysia has many potential mineral resources including some heavy and light rare earth element (HREE and LREE’s) minerals, such as Monazite and Xenotime. Their occurrence is in association with ores containing phosphates and oxides of Cerium (Ce), Lanthanum (La), Neodymium (Nd) and Thorium (Th). Mineralogical characterization of Malaysian Monazite concentrate for the recovery of Thorium dioxide (ThO2) has been carried out in this study. Scanning Electron Microscope (SEM) equipped with an Energy Dispersive X-ray Analyser (EDX) was used to assess the morphology and elemental composition of the mineral. The latter analysis showed that EDX surface analysis detected P-Kα Th-Mα, La-Lα, Ce-Lα and Nd-Lα as the major elements. The SEM micrographs with the EDX analysis revealed the morphological characteristics of Monazite which showed angled and irregular structures with dark coloured patches of Al, Si and Mn based inclusions. XRF analysis confirmed the presence of Th (8.52 wt.%) and U (0.25 wt.%). XRF also showed that the major rare earth elements (REE) of interest (> 5 wt.%) such as Ce, Nd and La were abundant in the mineral. XRD analysis identified LaPO4, CePO4 and NdPO4 as the major phases. Thorium phosphate (Th4(PO4)4) phase was not detected via XRD due to stronger X-ray reflection from the rare earth phosphates. The information collected from this study will help in developing a suitable process of treatment for the local Monazite, thereby facilitating the mineral to be used a domestic source of Th and other associated REE’s.

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.

Field-assisted sintering and phase transition of ZnS-CaLa2S4 composite ceramics

In the present study, zinc sulfide (ZnS) and calcium lanthanum sulfide (CaLa2S4, CLS) composite ceramics were consolidated via field-assisted sintering of 0.5ZnS-0.5CLS (volume ratio) composite powders at 800–1050°C. Through sintering curve analyses and microstructural observations, it was determined that between 800 and 1000°C, grain boundary diffusion was the main mechanism controlling grain growth for both the ZnS and CLS phases within the composite ceramics. The consolidated composite ceramics were determined to be composed of sphalerite ZnS, wurtzite ZnS and thorium phosphate CLS. The sphalerite-wurtzite phase transition of ZnS was further demonstrated to be accompanied by the formation of stacking faults and twins in the ceramics. It was also found that the addition of the CLS phase improved the indentation hardness of the ceramics relative to pure ZnS by homogeneous dispersion of ZnS and CLS small grains.

Fabrication and optimization of Cu(II) ion selective membrane electrode

In this study, the fabrication, performance characteristics and application of a Cu(II) ion selective pyridine based thorium(IV) phosphate membrane electrode are studied. The membrane electrode exhibited a fast response time of 10 s, the wide linear response in the concentration of 1 × 10–1 to 1 × 10–7 M of Cu (II) ions with a slope of 27.60 mV/decade change in concentration and a lifetime of 4 months. The potentiometric response revealed that the potentials are independent of pH in the wide range of 3.0–6.5. It was also used as an indicator electrode in the potentiometric titration of Cu(II) ions using ethylenediamine tetraacetic acid, disodium salt.

Sintering behavior of calcium lanthanum sulfide ceramics in field‐assisted consolidation

AbstractIn this study, calcium lanthanum sulfide (CaLa2S4, CLS) ceramics with the cubic thorium phosphate structure were sintered at different temperatures by field‐assisted sintering technique (FAST). Densification behavior and grain growth kinetics were studied through densification curves and microstructural characterizations. It was determined that the densification in the 850°C‐950°C temperature range was controlled by a mixture of lattice or grain‐boundary diffusion, and grain‐boundary sliding. It was revealed that grain‐boundary diffusion was the main mechanism controlling the grain growth between 950°C and 1100°C. The infrared (IR) transmittance of the FAST‐sintered CLS ceramics was measured and observed to reach a maximum of 48.1% at 9.2 μm in ceramic sintered at 1000°C. In addition, it was observed that the hardness of the CLS ceramics first increased with increasing temperature due to densification, and then decreased due to a decrease in dislocations associated with grain growth.

Cation-Dependent Structural Evolution in A2Th(TVO4)2(A = Li, Na, K, Rb, Cs; T = P and As) Series

A new alkali thorium phosphate family, A2Th(PO4)2 (A = Li, Na, K, Rb, Cs), has been synthesized and systematically investigated. The structural evolution of this new family was compared with that of the previously reported arsenic-based family A2Th(AsO4)2 (A = Li, Na, K, Rb, Cs). Similar compositions of the phosphorus- and arsenic-containing series allowed their direct comparison in order to reveal the influence of the size and nature of either monovalent or pnictogen cations on the crystal structure and related properties. Detailed crystal chemical analyses suggest that two main driving forces are in charge for the structural evolution, i.e., the size of alkali cations as well as the local environment of the thorium polyhedra and the TO4 (T = P, As) tetrahedra. Raman spectra were measured for all studied phases and bands have been assigned. The density functional theory calculations revealed that the local environment of the PO4 tetrahedra may be responsible for shifts of PO4 vibrational bands observed i...

Solubility product of the thorium phosphate hydrogen-phosphate hydrate (Th2(PO4)2(HPO4)·H2O, TPHPH)

The standard solubility constant of TPHPH, Th2(PO4)2(HPO4)·H2O was evaluated at 298K by performing dissolution experiments of a synthetic sample in different nitric acid solutions at a constant ionic strength of 1molL−1. The average value of the solubility constant and the associated expanded uncertainty U(log10Ks,0∘ (298K), 0.95 level of confidence) were evaluated to log10Ks,0∘ (TPHPH, 298K)=−(71.2±1.3), while the ΔfG∘ (TPHPH, 298K) value reached −(5200±23)kJ·mol−1. From the experiments performed at different temperatures, the standard molar enthalpy as well as the standard molar entropy of the dissolution reaction was determined. The solubility of TPHPH was found to be retrograde over the investigated range of temperatures (298–363)K. The values of the standard enthalpy of formation and the standard molar entropy of TPHPH are equal to: ΔfH∘(TPHPH)=-(5640.5±16.0)kJ·mol-1 and Sm=(298±68)JK−1mol−1, respectively.

Turmeric/polyvinyl alcohol Th(IV) phosphate electrospun fibers: Synthesis, characterization and antimicrobial studies

Turmeric/polyvinyl alcohol (PVA) thorium(IV) phosphate hybrid cation exchange nanofibers were prepared for wastewater treatment along with antimicrobial activity. The physicochemical properties of electrospun fibers like thermal stability, surface morphology and composition were evaluated by using thermogravimetric analysis/differential thermal analysis/differential thermogravimetry (TGA/DTA/DTG), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transforms infra red (FTIR), and energy dispersive X-ray (EDX) techniques. The ion exchange capacity determined by volumetric analysis was found to be 1.98meq dry/g of ion exchanger. Antimicrobial properties of turmeric/PVA Th(IV) phosphate hybrid cation exchange electrospun fibers were validated by agar-well diffusion test (ADT) and microtitre plate assay (MPA) analyses. The presence of turmeric in polyvinyl alcohol Th(IV) phosphate hybrid cation exchange nanofibers is responsible for antimicrobial properties. The maximum zone of inhibition was found to be 22mm for E. coli at 50µg/ml and 21mm for S. aureus at 100µg/ml.

Thorium (IV) phosphate‐polyaniline composite‐based hydrophilic membranes for bending actuator application

In the present study, ionic polymer metal composite (IPMC) membrane actuator based on triple‐layered thorium(IV) phosphate/polyaniline/Pt (ThP‐PANI‐Pt) was prepared via consecutive solution recasting and electroless plating methods. The triple‐layered membrane is composed of thorium(IV) phosphate (ThP) inorganic cation exchanger layer in the middle section, two layers of polyaniline deposited through in situ polymerization and finally Pt electrode layers on both the surfaces on the outer section. The water uptake capacity of the ThP‐PANI composite polymer membrane was found to be 95.40% at 45ºC for 10 h of immersion time. The ion exchange capacity and proton conductivity was found to be 1.6 meq g−1of dry membrane and 1.12 × 10−3 S cm−1, respectively. Maximum water loss from IPMC was 38% at 4 V for a time period of 12 min. Scanning electron micrographs shows the smooth and uniform coating of Pt on both side of composite polymer membrane surfaces. Cyclic voltammetry, linear sweep voltammetry, transmission electron microscopy, Fourier transforms infrared spectroscopy, thermal gravimetric analysis, X‐ray diffraction, and tip displacement of ThP‐PANI‐Pt IPMC membrane actuator was also examined. POLYM. ENG. SCI., 57:258–267, 2017. © 2016 Society of Plastics Engineers