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This study employs a combination of texture and composition of allanite to investigate the chemical evolution of rare earth elements (REEs) in the hydrothermal veins within the Chhotanagpur Granite Gneiss Complex around Kalapathar area, Purulia district, West Bengal, India. Allanite occurs as pockets and lumps in the hydrothermal veins. Locally, the allanite pockets/lumps have high concentrations of REEs (∑REEs ~9.8 wt.%), Th (up to 1427.2 ppm) and U (up to 642.1 ppm). Three hydrothermal fluids and associated REE mobilization have been distinguished and characterized. The hydrothermal fluid1 causes metasomatic addition of REEs that leads to the formation of early REE-enriched allanite. Hydrothermal fluid2 imposed changes in the texture and composition of the allanite where the early allanite was replaced by relatively REE-depleted allanite following the substitution scheme REE+3 + (Fe+2, Mg+2) → Ca+2 + (Al, Fe+3). The hydrothermal fluid3 is marked by the alteration of allanites to the bastnaesite and monazite. REEs have been transported mainly in aqueous chloro-complexes with high to moderate salinity and low homogenization temperature (257°–361°C). The timing of the hydrothermal event is established through U–Th–total Pb dating of monazite, yielding at around 875 ± 43 Ma. Research highlights: The allanite clots and lumps in hydrothermal veins within CGGC around Kalapathar, Purulia District, West Bengal display high ∑REEs up to 9.8 wt.% along with Th and U up to 1427.22 and 642.14 ppm, respectively. The hydrothermal event has been characterized linked with two distinct varieties of allanite growth. The transportation of REEs occurs in aqueous chloro-complexes during the hydrothermal event. The timing of hydrothermal events and growth of the allanites has been determined. REE-enriched magmatic intrusion. [ABSTRACT FROM AUTHOR]

The hydrogen-based mineral phase transformation-flotation process can realize the efficient development of iron-bearing rare earth ores. The isothermal and non-isothermal decomposition mechanisms of bastnasite in the hydrogen atmosphere were studied to optimize the hydrogen-based mineral phase transformation process. The thermal decomposition of bastnasite first produced REOF, which would react with oxygen to produce rare earth oxides and fluorides during the analysis process. The thermal decomposition was an endothermic reaction, and the generated gas were mainly CO 2 and trace CO, with a mass loss of about 20%. Increasing the temperature can greatly promote the thermal decomposition. After thermal decomposition, the particles showed a layered structure, and many parallel slits run through the particles. The porosity and specific surface area of the particles were significantly improved. The apparent activation energy of isothermal decomposition was 71.80 ± 5.40 kJ/mol, and the kinetic mechanism was random nucleation and growth model (n = 2). The apparent activation energy of non-isothermal decomposition was 201.96 kJ/mol, and the kinetic mechanism was phase-boundary controlled reaction mechanism (n ≈ 2). [Display omitted] • Bastnaesite thermally decomposes in H 2 to form REOF, which is easy to be oxidized. • The thermal decomposition reaction of bastnaesite in H 2 is endothermic. • The particles exhibit a layered structure with a high specific surface area after decomposition. • The isothermal and non-isothermal decomposition kinetic mechanisms were determined. [ABSTRACT FROM AUTHOR]

A novel environmentally friendly one-step decomposition strategy for mixed rare earth concentrate of Bayan Obo in sulfuric acid solution was proposed in this work. In this process, more than 84% of bastnasite and monazite were decomposed in the leaching step at a temperature lower than the boiling point of sulfuric acid solution. So, the dilapidation of sulfuric acid in this current proposed process will be reduced to a large extent. The stability region of rare earth ion in the RE(La, Ce, Nd)-F-P-SO4-H2O system at 170 °C has been proven through Eh-pH diagrams. The factors influencing decomposition of rare earth concentrate in this process were also investigated and the optimal leaching conditions were determined to be a leaching temperature of 170 °C with an ore/acid ratio of 1:5 (g/mL), a sulfuric acid concentrate of 75% and a leaching time of 80 min. The mineralogical changes occurring during the H2SO4 leaching process were investigated by X-ray diffraction and SEM-EDS. The analysis results showed that bastnasite and most of monazite had been decomposed, leaving only a small amount of monazite in the leaching residue. [ABSTRACT FROM AUTHOR]

To overcome the difficulty of separating bastnaesite from fluorite through the flotation technique, the present study examined the suitability of sodium alginate (SA) as a depressant in the flotation process. The effect of SA on the flotation separation of bastnaesite and fluorite was evaluated using micro-flotation tests, zeta potential measurements, adsorption density measurements, Fourier infrared spectroscopy, and X-ray photoelectron spectroscopy. The micro-flotation results showed that SA exerted a strongly detrimental effect on fluorite flotation, while slightly affecting bastnaesite flotation. The surface chemistry results revealed that the -COO- and HO- functional groups in SA coordinated with Ca2+ on the fluorite surface, which induced hydrophilicity and hindered adsorption in the subsequent octylhydroxamic acid as a collector. However, the interaction of SA with the bastnaesite surface was marginal and did not affect the anchoring of the collector on the surface of bastnaesite. Based on these results, the present study proposes a possible model for the interaction of SA on the surfaces of the two minerals, laying a foundation for the flotation separation of bastnaesite from fluorite with SA as an environmentally benign depressant. [ABSTRACT FROM AUTHOR]

Fluorite, a strategic industrial mineral, was investigated for flotation separation from bastnaesite with tannic acid (TA) as depressant. In this study, the adsorption analysis indicates that the adsorption density of TA on bastnaesite was greater than that of fluorite. The zeta potential, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) provide the evidence that chemisorption and electrostatic attraction occurred simultaneously between TA and fluorite or bastnaesite at optimal pH, the latter also involving hydrogen bonding interactions. Furthermore, the micro-flotation and batch flotation results suggest that TA could effectively depress bastnaesite with a negligible effect on fluorite at low concentrations, and that TA attached to the surface of bastnaesite precluded the adsorption of phthalic acid (PA) as collector, whereas it could be adsorbed on the fluorite surface. These findings offer a robust theoretical foundation and valid guidance for the flotation separation of fluorite from bastnaesite in industrial processes. [ABSTRACT FROM AUTHOR]

The large loss of fine-grained bastnaesite has become an increasingly important issue restricting the development of rare earth ore flotation industry. To solve this issue, a new collector mixture that combines octyl hydroxamic acid (OHA) and octyl phenol ethoxylation (OP10, the number of ethylene oxide groups is 10) is proposed to be used to improve the flotation of bastnaesite. The flotation adsorption mechanism of OHA/OP10 on bastnaesite was investigated by a series of experimental and analytical tests. The results showed that when the molar ratio of OHA/OP10 was 3:1, the OHA/OP10 combination significantly improved the recovery of −74 + 38 μm and −15 μm bastnaesite compared with only OHA. Optical microscopy revealed that mixed OHA/OP10 had a beneficial effect on fine-grained bastnaesite aggregation. In addition, the results of the zeta potential test, fluorescence spectrum analysis, and XPS analysis showed that OHA and OP10 were co-adsorbed on the surface of bastnaesite. [ABSTRACT FROM AUTHOR]

The recovery of rare earth elements from ores is crucial because of their applications in modern technology. Bastnaesite (La/Ce(CO3)F) is typically found in deposits with other gangue minerals but can be purified by flotation. Accordingly, we investigated the interactions of the collector nonyl hydroxamic acid (NHA) with bastnaesite using density functional theory (DFT) calculations. In addition, we replaced Ce sites on the bastnaesite (100) surface with La and investigated the effect on NHA adsorption. Finally, we examined the effects of co-present aluminum species, which are frequently used inhibitors for associated gangue minerals during bastnaesite flotation, on NHA adsorption and, thus, the flotation efficiency. We found that doping with La increased the strength of adsorption between NHA and the bastnaesite (100) surface. In addition, we found that Al(OH)3(s) was adsorbed more strongly than NHA. Consequently, when Al(OH)3(s) is present in the flotation pulp, it is preferentially adsorbed, which reduces the number of sites for NHA adsorption and its flotation efficiency. These findings suggest that La doping can enhance the recovery of bastnaesite and indicate that the presence of Al minerals should be minimized. [ABSTRACT FROM AUTHOR]

During the flotation separation process of bastnaesite, it is difficult to separate bastnaesite from fluorite effectively. In this present study, sodium silicate (SS) can effectively improve the flotation separation effect of bastnaesite and fluorite in salicylhydroxamic acid (SHA) systemasa. Through relevant analyses, such as Zeta potential measurements, adsorption capacity tests, Fourier transform infrared (FTIR) spectroscopic analyses and X-ray photoelectron spectroscopy (XPS) tests, the selective suppressor of SS on fluorite was proven. At pH 10, the single mineral flotation results show that with the increase of SS dosage, the flotation recovery of fluorite rapidly decreases from 61.5% to 35.31%, while the flotation rate of bastnaesite is still high (recovery is 80.02%). Then, the experiment of artificial mixed ore proved that the flotation separation of fluorite and bastnaesite was effective under the appropriate dosage of inhibitor. The results of potentiodynamic measurement and an adsorption capacity test showed that the SiO OH 3 − structure of SS more easily reacted with fluorite, which further prevented the adsorption of SHA on the fluorite surface. FTIR test results and XPS analysis further showed that SS had a strong binding effect with the Ca site on the fluorite surface, but a weak binding effect with the Ce site on the bastnaesite surface. Consequently, SS can be used as an effective inhibitor in the flotation separation of fluorite and bastnaesite. [ABSTRACT FROM AUTHOR]

Rare earth elements (REEs) are widely used in high-tech industries and are important basic raw materials. Bastnaesite is one of the most important minerals used in the rare earth extraction industry, and the efficient development of it is the key guarantee for the safe supply of rare earth raw materials. In this study, a novel method for dissolving bastnaesite using a carboxyl-functionalized ionic liquid ([Hbet][Tf2N]) is proposed. This innovative method provides a collaborative model with the dissolution and synchronous extraction of rare earth elements during the heating and cooling of the [Hbet][Tf2N]–H2O system. In the heating process, rare earth elements can be dissolved in a weakly acidic environment of ionic liquid without the trouble of HF escaping, and the leaching efficiencies of rare earth elements are above 95%. During the cooling of the leaching system, the rare earth ions in the dissolved state are extracted into the ionic liquid phase due to the two-phase stratification of [Hbet][Tf2N] and aqueous solution. It has been proved that rare earth ions recovery and ionic liquid regeneration can be achieved by back extraction using oxalic acid for the REEs-loaded ionic liquid. [ABSTRACT FROM AUTHOR]

A stable microemulsion system is constructed by choosing α-aminophosphonate extractant Cextrant 230 and an anionic surfactant sodium bis (2-ethylhexyl) sulfosuccinate (AOT) as the cosurfactants. The effects of some factors such as pH and the concentration of Cextrant 230, AOT, NaOH and the sulfate in the aqueous solution on the maximum water ratio (x0) are studied. The process and effects of microemulsion formation are analyzed and the optimized conditions for the stable microemulsion are determined. The Cextrant 230-AOT-nheptane microemulsion system is applied for the extraction of thorium. The effects of emulsion-to-water volume ratios, the concentrations of Cextrant 230, AOT and sulfate, temperature are studied. The extraction rate of thorium in the microemulsion system increases with the increase of the concentration of Cextrant 230 (or AOT), which is significantly higher than that of AOT-n-heptane microemulsion system. Cextrant 230 and AOT have a synergistic effect on the extraction of thorium. Temperature has little effect on extraction of thorium and the reaction is entropy-driven. Upon the comparison of the stripping of thorium by different inorganic acids, sulfuric acid is chosen as the stripping reagent. The loading capacity for ThO2 is about 1. 43 g/L. This microemulsion system is applied to the separation of Th from the actual bastnaesite sulfate leach liquid after the cerium extraction and the thorium content can be reduced to less than 0. 1 mg/L. The microemulsion system has both the advantages of thermodynamic stability and high efficiency. [ABSTRACT FROM AUTHOR]

Rare minerals represented by oxides, fluorides, F-carbonates and REE arsenates in association with monazite-Ce, monazite-Th, xenotime-Y and zonal REE fluorite were identified in the rare-metal ores of the Sn–W deposits of Lesser Khingan, Amur region. Rare lanthanide minerals are described, including fluocerite, bastnaesite, and gasparite-Ce, which was found for the first time in Russia in the Sn–W greisens, and chernovite-Y, the second find in the greisens of the Russian Far East. The influence of arsenic fluids at the late hydrothermal stage caused the replacement of xenotime-Y and monazite-Ce by diverse REE minerals with different lanthanide proportions. It is found that these minerals differ in chemical composition from the same minerals described in other deposits elsewhere. Due to the variable valence state of arsenic and the complete isomorphism between rare earths, arsenates can be used as indicators of redox conditions of their deposition. [ABSTRACT FROM AUTHOR]

Bastnaesite is an important mineral geochronometer to record the REE mineralization time for REE deposits. As the only reliable primary standard for in situ U–Th–Pb dating, bastnaesite K-9 is inhomogeneous and nearly out of supply. The accurate in situ U–Th–Pb dating of bastnaesite and its wide application are still constrained by the lack of reliable reference materials. Therefore, a potential primary standard was proposed and assessed in thirty-one ablation settings in this paper. The normalized 206Pb/238U and 208Pb/232Th ratios (i.e., 206Pb/238U and 208Pb/232Th fractionation) of xenotime XN01 are respectively similar or slightly different from those of bastnaesite K-9 in most ablation settings. The average value (i.e., calibration factor) of 206Pb/238U and 208Pb/232Th ratios for XN01 is consistent with those for K-9 with the offsets of <2.4% in the same ablation setting when using the ratio-of-the-mean intensity method for data reduction. Thus, the most obtained ages of K-9 calibrated by XN01 are consistent with its reference age of 118 ± 1 Ma with the offsets of <2%. Moreover, four typical bastnasite samples were analyzed in three normal ablation settings. Their respective U–Pb and Th–Pb ages calibrated by XN01 were consistent with those by K-9 within uncertainty. Because of high Th contents (>4500 ppm) and Th/U ratios (>400), the Th–Pb ages of these young samples are acceptable and agree well with their respective published Th–Pb ages within uncertainty. Therefore, the matrix effect between xenotime XN01 and bastnaesite can be neglected normally. Xenotime XN01 is more uniform than K-9 and can serve as a primary reference material for the in situ U–Th–Pb dating of bastnaesite. Moreover, bastnaesite Zagi has a sufficient reservoir, uniform Th–Pb, corrected U–Pb ages, and can serve as a secondary reference material for quality control. [ABSTRACT FROM AUTHOR]

In this study, 2-hydroxy-3-naphthalene hydroxamic acid (NHA) was used as a collector in microflotation experiments. By comparing the flotation performance of NHA with that of sodium oleate (NaOL) and salicylhydroxamic acid (SHA) commonly used in industry, the performance of NHA in the flotation separation of bastnaesite and calcite was studied. Potentiodynamic (zeta) measurements, Fourier transform infrared spectroscopy (FTIR) measurements and X-ray photoelectron spectroscopy (XPS) measurements were used to reveal the interaction mechanism of bastnaesite with NHA. The results of the pure mineral microflotation test showed that when the pH value was 9 and the dosage of NHA was 4.0 × 10−4 mol/L, the recovery of bastnaesite reached 93.5%. A concentrate with a bastnaesite grade of 87.08% was obtained from the flotation test of artificially mixed ore, and the recovery of bastnaesite was 90.83%. The zeta measurements and FTIR experiments showed that NHA adsorbed onto the surface of bastnaesite, which changed the surface state of bastnaesite. XPS testing showed that NHA chemically adsorbed onto the bastnaesite, and Ce3+ formed a chelated structure with − C (OH) = NO − . The hydrophobicity of the surface of bastnaesite was improved, which made it easier for bastnaesite to adhere to the slurry surface by bubbles. At present, most of the domestic methods for recovering fine-grained bastnaesite use flotation recovery. Calcite and other gangue minerals inevitably enter into the concentrate resulting in low-grade REE concentrate. [ABSTRACT FROM AUTHOR]

High gradient magnetic separation (HGMS) is an effective method to recover fine weakly magnetic particles from suspension. The structural parameters of the magnetic matrix have a great influence on the distribution of the magnetic field in the separation space, which in turn affects the separation effect. This study investigated the magnetic adsorption behavior of high-gradient magnetic separator magnetic matrix parameters on different particle sizes of bastnaesite. Bastnaesite was obtained from Maoniuping, Sichuan, through experimental data and simulation analysis, the effects of structural parameters such as distance between equidistant ring-shaped bulges (ERB) and column gap between adjacent rods on the magnetic adsorption behavior of minerals with different particle sizes were investigated，and the force distribution of magnetic particles in the sorting space was analyzed. The results indicate that at any distance between ERB, the magnetic particle trapping effect of the staggered arrangement matrix is significantly superior that of parallel arrangement. Moreover, a column gap of 2 or 3 mm for the magnetic rods significantly outperforms trapping with a column gap of 4 or 5 mm. Under any rod gap, the trapping effect of the screw-thread rod matrix is better than that of the conventional rod matrix with the same diameter. In particular, the matrix has the optimal trapping effect on magnetic particles when the ERB distance is 1 mm. By analyzing the force distribution of bastnaesite in the sorting space, it is found that the matrix has poor trapping effect on fine-grained mineral particles. Under the same mineral particle size, increasing the magnetic field intensity can improve the recovery of useful minerals. [Display omitted] • The magnetic capture behavior of bastnaesite is studied by screw thread rod matrix. • The effect of matrix structural parameters on bastnaesite is preliminary determined. • The force of bastnaesite particles is analyzed by calculation. • The results of the bastnaesite test prove that the calculations are credible. [ABSTRACT FROM AUTHOR]

The Mn/bastnaesite concentrate and Mn/Al 2 O 3 catalysts were prepared by impregnation method, and their NH 3 -SCR denitrification performance was tested. The results showed that the Mn/bastnaesite concentrate catalyst achieved up to 95% NO conversion rate at 150 °C, and the Mn/Al 2 O 3 catalyst reached 76% at 300 °C. A series of characterisation results showed that the bastnaesite concentrate can better interact with MnOx species and promote mutual dispersion compared to Al 2 O 3. The Mn/bastnaesite concentrate has a stronger redox capacity, and good NH 3 and NO adsorption capacity at low temperatures. The multi-element coexistence system of bastnaesite concentrate itself is a significant advantage of its use as a carrier. In-situ Fourier transform infrared (FTIR) results showed that the Mn/bastnaesite concentrate catalyst follows an L-H mechanism throughout the reaction, with NH 4 + species in the Brønsted acidic site on the catalyst surface being the main reactant species. Most of NO is converted to monodentate nitrite, which is formed by bonding with Mn3+ provided by the supported Mn species, rare earth elements and transition metal ions contained in the carrier itself to form O–N–O–Mn3+ intermediates, which participate in the reaction together, and then combined with the adsorbed NH 4 +/NH 3 species to produce N 2 and H 2 O. An E-R mechanism was also present on the catalyst surface, NO participates directly in the reaction in gaseous form, and the NO [NH 2 ](ads) intermediate species produced by interaction with NH 4 + species in the acidic position of Brønsted was further decomposed to N 2 and H 2 O. By comparing the reaction mechanism with the commonly used catalyst carrier Al 2 O 3 for NH 3 -SCR, it can be concluded that bastnaesite concentrate as a carrier not only has the performance of conventional carriers, but also has certain catalytic activity and can interact with the active components to give it excellent performance, which provides a theoretical basis for rare earth minerals as denitrification catalysts. • The first use of bastnaesite concentrate from Baiyun Ebo as a carrier for NH 3 -SCR catalysts. • Mn/bastnaesite concentrate Catalyst with Excellent Low Temperature Denitrification Performance. • The Ce 7 O 12 species has a better mutual promotion with Mn. • The Mn3+ will bond with the monodentate nitrate species to form O–N–O–Mn3+ species involved in the reaction. • Mn/bastnaesite concentrate surface was a dual-mechanism coexistence with more reaction pathways. [ABSTRACT FROM AUTHOR]

In order to improve the recovery of rare earth elements, finding a collector with a strong selectivity ability had become the focus of research. In this paper, phenylpropyl hydroxamic acid (PHA) was used as a new hydrophobic surfactant collector for the separation of bastnaesite from calcite, and salicylic hydroxamic acid (SHA) was used as a reference collector. The results of a single mineral flotation test with SHA show that the reagent has good collection performance and selectivity. In addition, Zeta potential measurements and FTIR analysis show that PHA is adsorbed on the surface of bastnaesite by chemical adsorption, and the surface state of bastnaesite changes after PHA treatment. By XPS analysis, PHA interacts with Ce, and forms a Ce–O bond with Ce. It is speculated that the hydroxamic acid forms a five-element-chelated hydroxamic group with Ce on bastnaesite surface, so as to improve the hydrophobicity of bastnaesite, and make bastnaesite float more easily out of the pulp. According to DFT calculation, PHA has better adsorption capacity and stronger hydrophobicity than SHA, and shows superior electronic group capacity and chemical reactions that promote its flotation performance. [ABSTRACT FROM AUTHOR]

BACKGROUND: With the increasing demand for scandium resources, countries around the world have carried out scandium metallogenic mechanism research and prospecting in recent years. One of the key research contents is to clarify the occurrence characteristics of scandium. According to previous studies, scandium mainly exists in the form of isomorphism and ion adsorption in various scandium deposits. At present, more than 800 kinds of scandium-bearing minerals have been found. The scandium resource of the Bayan Obo deposit is large, which has the characteristics of dispersed distribution and low content. Scandium enters other minerals in the form of isomorphism and no independent scandium mineral is found. Due to the limitation of testing technology and sampling, there is no accurate quantitative research to systematically explore the occurrence characteristics of scandium in different minerals in the Bayan Obo deposit. Therefore, the identification of the main scandium-bearing minerals is insufficient, which is not conducive to further exploration of the enrichment mechanism of scandium and the utilization of scandium resources in the deposit. OBJECTIVES: To understand the occurrence of Sc in different minerals of the Bayan Obo deposit. METHODS: 34 kinds of minerals in the Bayan Obo deposit were systematically determined by electron probe microanalyzer (EPMA) technology. RESULTS: The test results showed that the average scandium content (Sc2O3) in 6 minerals was more than 0.100%. They were samarskite (with average Sc2O3 content of 2.485%), columbite (1.263%), manganocolumbite (0.251%), dark purple fluorite (0.181%), thorianite (0.145%) and Y-rich aeschynite (0.124%) from high to low. Samarskite had the highest scandium content (3.093%). The content of scandium in 16 minerals ranged from 0.004% to 0.067%, which were fergusonite (with average Sc2O3 content of 0.067%), alkaline amphibole (0.062%), ferrothorite (0.060%), pyrochlore (0.049%), fersmite (0.031%), bastnaesite (0.028%), apatite (0.028%), britholite (0.025%), monazite (0.023%), aegirine (0.02%), biotite (0.019%), humite (0.011%), fergusonite-(Ce) (0.008%), feldspar (0.007%), magnetite (0.005%), albite (0.004%). Scandium was not detected in the other 12 minerals. CONCLUSIONS: Samarskite has the highest scandium content in the deposit, and the 6 main scandium-bearing minerals are samarskite, columbite, manganocolumbite, dark purple fluorite, thorianite and Y-rich aeschynite. Among the 34 minerals, the content of scandium in 22 minerals is higher than the detection limit of EPMA, and scandium is distributed in a dilute manner. The occurrence of scandium is related to titanium, yttrium and thorium, and the correlation coefficients are 0.869, 0.835 and 0.720, respectively. Scandium is closely related to niobium minerals such as columbite, manganocolumbite, fersmite and Y-rich aeschynite. It can be considered to comprehensively utilize scandium and niobium resources at the same time. [ABSTRACT FROM AUTHOR]

In this paper, CePO4 and CeCO3F were prepared by hydrothermal synthesis based on the ratio of bastnaesite to monazite in the process mineralogy of Baiyun Ebo rare earth concentrate. A comparison of the two treatments, ball milling and ball milling sulphation, revealed that the denitrification efficiency of the catalysts treated with ball milling sulphation increased by 20 percentage points, compared to those treated without sulphation, with denitrification efficiencies of up to 80%. The surface properties, redox properties and catalytic mechanism of the samples before and after the sulphation treatment were analyzed, by using XRD, NH3-TPD, H2-TPR, XPS and in situ IR characterization. The results showed that the CeF3 diffraction peaks in the XRD patterns disappeared in the sulphated samples, NH3-TPD showed that the adsorption capacity of NH3 on the surface of the samples was enhanced, and the introduction of sulphuric acid provided a large number of acidic sites on the catalyst surface, among which the Lewis acidic sites might be more favorable for the promotion of SCR reaction. The acidification of sulphuric acid greatly increases the redox capacity of the catalyst, and the interconversion between Cen+ was enhanced. XPS showed a significant increase in the amount of adsorbed oxygen on the surface of the sample. The presence of -NO2, an important intermediate in the L-H mechanism, was also detected by IR analysis. reactant species during the L-H mechanism reaction were monodentate nitrate, bridged nitrate and NH4+ species produced by NH3 adsorption on the Brønsted acidic site of the catalyst surface. [ABSTRACT FROM AUTHOR]

The stability relations of cerium and its species in the hydrometallurgical processing of bastnasite were studied using Pourbaix diagrams. Different systems of Ce-(F)-(CO3)-(SO4)-(C2O4)-H2O were constructed using HSC Chemistry software with the necessary thermodynamic data. The Ce-F-H2O system exhibits a large stability region for CeF3 (pH∼ −1.5 – 12). The stability domain of was determined by Ce-CO3-H2 system in the pH of 4.5 – 12. The decomposition behaviours of CeFCO3 were studied by Ce-F-CO3-H2O system which shows the stability domain of CeFCO3 from neutral to basic media. The treatment of CeFCO3 with H2SO4 was investigated by depicting diagrams of Ce-F-CO3-SO4-H2O system. According to this system, CeFCO3 can be decomposed to produce soluble Ce sulphates at around pH 6.2. In contrast, alkaline treatment of CeFCO3 converts it to Ce(OH)3 at pH 11. Finally, the recovery of Ce by oxalate precipitation was studied by Ce-C2O4-H2O system which showed the domain of Ce oxalate decahydrate. [ABSTRACT FROM AUTHOR]

A new approach was employed in explaining the weak ferromagnetic behavior of conventionally synthesized Zr4+ modified Bi0.8La0.2FeO3. Rietveld refinement of XRD patterns revealed a polar-tonon-polar R3c → Pnma structural transition in Zr4+substituted samples. Magnetic properties were discovered to be remarkably enhanced, with extracted coercivity and remanence as high as 14 kOe and 0.2 emu/g, respectively. More importantly, an answer to the essential question of the magnetic domain state of the samples has been put forward. Our analysis established, nearly without doubt, the presence of grains consisting of a single magnetic domain. Separated ferromagnetic and anti-ferromagnetic components of the total M-H curves helped to reveal an immense effect of the structural transition on the shape of the hysteresis loops. The orthorhombic magnetocrystalline anisotropy of the Pnma phase has been primarily deemed responsible for the high coercivity and remanence of the Zr4+ modified samples. The effect of the grain size and Fe-O-Fe bond angle on the magnetic properties of the samples has also been discussed. Ferroelectricity was found to be absent in Zr-substituted samples because of their non-polar structure. However, the leakage current was reduced by up to two orders of magnitude compared to Bi0.8La0.2FeO3 upon addition of Zr4+. Dielectric measurements conformed to the ferroelectric and leakage current characteristics, and Zr4+ substitution was again found to be beneficial. [ABSTRACT FROM AUTHOR]

[Display omitted] • NHOO is developed utilizing the molecular framework of octyl hydroxamic acid (OHA). • NHOO has a better selectivity in bastnaesite/fluorite separation relative to OHA. • NHOO shows a higher adsorption amount on bastnaesite surface relative to fluorite. • NHOO is capable of creating a pentacoordinate ring with a Ce3+ ion on bastnaesite. • NHOO solely has the ability to develop a single bond with a Ca2+ ion on fluorite. Bastnaesite has always been faced significant challenges in its flotation separation from its associated gangue minerals like fluorite. Despite being a commonly employed collector for oxide mineral flotations, octyl hydroxamic acid (OHA) still exhibits insufficient selectivity. Consequently, a novel hydroxamic acid, N -[6-(hydroxyamino)-6-oxohexyl]octanamide (NHOO), is synthesized and employed as a collector in bastnaesite flotation, building upon the structure of OHA. Flotation experiments under neutral conditions demonstrate the effective ability of NHOO to achieve a difference of nearly 60% in the recoveries between bastnaesite and fluorite during their separation. Concordant outcomes from zeta potential characterizations, adsorption tests, and X-ray photoemission spectroscopy validate heightened adsorption quantities of NHOO on bastnaesite surface relative to fluorite under identical dosage conditions. Ab initio calculations unveil the capability of NHOO to establish a pentacoordinate chelate ring on bastnaesite surface, whereas on fluorite, it can only form a singular chemical bond. Consequently, NHOO shows a considerably lower energy associated with its adsorption on bastnaesite surface in comparison to its energy on fluorite surface. [ABSTRACT FROM AUTHOR]

In the Sn–W greisen deposits of the Karadub ore field, rare arsenates of REEs chernovite-(Y) and gasparite-(Ce), associated with topaz, fluorite, fluocerite, and bastnaesite, have been identified. They replace early xenotime-(Y) and monazite-(Ce). Chernovite-(Y) and gasparite-(Ce) from Sn–W greisens differ in their chemical composition from the same minerals previously described elsewhere. Chernovite-(Y) differs in the minimum content of Y with only 0.47 to 0.26 atoms in the formula (a.p.f.) and a relatively high content of light REEs of 0.111–0.254 (a.p.f.). Gasparite-(Ce) has a high Nd content of 0.28 (a.p.f.). REE arsenates were formed by substituting xenotime (Y), monazite (Ce), and REE-bearing fluorite under strongly oxidizing conditions. [ABSTRACT FROM AUTHOR]

Intrusive granitoid bodies and quartzofeldspathic gneiss outcrops in the Guwahati and Mayong areas are considered part of the northern extension of the basement gneissic complex of the Shillong Plateau. They are medium to coarse-grained porphyritic granitoids essentially composed of quartz, K-feldspar, plagioclase, biotite, hornblende, sphene, magnetite, apatite, zircon, allanite, and bastnaesite in different proportions. Mineralogical characteristics of these granitoids reveal that they are monzogranite. The biotites are re-equilibrated in Guwahati granitoids whereas they are primary in Mayong granitoids. Ti-in biotite, Al-in hornblende and mineral assemblage biotite-K-feldspar-magnetite were used to determine temperature, pressure and oxygen fugacity during the crystallization of parent magmas. The Guwahati granitoids crystallized and re-equilibrated at temperatures ranging between 602°C and 752°C (avg. 685°C) with pressure (5.2–5.6 kbar, avg 5.4 kbar) from low oxidized magmas (log fO2 −16.33 to −14.36 bar), buffered below FMQ to within NNO. The Mayong granitoids crystallized at temperatures range 694°C to 715°C (avg. 705 °C) with pressure (4.7 to 5.1 kbar, avg. 5 kbar) under reduced oxidized condition (log fO2 −17.88 to −17.62 bar) buffered below FMQ. The calc-alkaline nature, low to moderate oxygen fugacity and high H2O (4.5–7.4 wt%) content suggests that Guwahati granitoids emplaced in subduction-related tectonic setting whereas alkaline nature, reduced oxygen fugacity and low content of H2O (2.15 wt%) suggest anorogenic tectonic setting for Mayong granitoids. Also, from the estimated pressure and depth of emplacement conditions it suggests that both the granitoids are mid-level plutons. [ABSTRACT FROM AUTHOR]

The production of mixed rare earth oxide powder from a thorium containing bastnasite ore by sulfuric acid bake-water leaching followed by precipitation with oxalic acid and thermal decomposition of the oxalates was investigated. The sulfuric acid baking was performed at 250 °C and the optimum baking time was found to be 3 h. Using deionized water as lixiviant, 92.6% La, 86.8% Ce, 86.9% Pr, 82.3% Nd, 95.4% Th and 31% Y were dissolved from the baked ore at 25 °C after 30 min of leaching. The effect of solid-to-liquid ratio on the dissolution of the rare earth elements and thorium shows that when the solid ratio in the water increased from 1:10 to 1:3, the dissolution percentage decreased. The final mixed rare earth oxide powder contained 88.54% REO and 6% ThO 2 together with small amounts of other impurities. The SEM mapping results revealed that the produced REO has an irregular crystal shape. Based on the experimental results obtained from the current study, a flowsheet was proposed for the production of mixed rare earth oxide powder from a specific complex bastnasite ore. Unlabelled Image • The production of mixed rare earth oxide powder from a thorium containing bastnasite ore was investigated. • 92.6% La, 86.8% Ce, 86.9% Pr, 82.3% Nd, 95.4% Th and 31% Y were extracted by acid bake-water leach process. • 99.8% Ce, 99.7% La, 97.3% Nd, 98.1% Pr, 91.7% Y and 97.4% Th were co-precipitated by oxalic acid. • The final product contains 88.54% REO and 6% ThO 2. • The REO powder has an irregular crystal shape. [ABSTRACT FROM AUTHOR]

• Flotation of bastnaesite suffers from high reagent consumption and complex stages of high-temperature conditioning due to the similar surface characteristics of bastnaesite and associated gangue minerals, including calcite. This research seeks to develop a sustainable flotation reagent scheme for the optimal recovery of bastnaesite using organic acids as depressants and sodium oleate as the collector. • As such, systematic flotation experiments were conducted to investigate the impact of pH, collector dosage, and organic acids concentration on the flotation performance of bastnaesite when calcite exists as the primary gangue mineral. The selective flotation of bastnaesite from calcite has been studied by micro-flotation, zeta potential, adsorption density measurements, and XPS characterization using organic acids, namely lactic acid and succinic acid, as depressants and NaOL as the collector. • The results of flotation tests indicated that the addition of lactic and succinic acids dramatically reduced the recovery of calcite while remaining impotent to the recovery of bastnaesite. The data demonstrated that both organic acids are selective depressants for calcite. At the optimal level of pH, sodium oleate and organic acid dosages, the recovery of calcite was reduced to below 10% and 20%, where bastnaesite recovery remained above 85% and 90% when succinic acid and lactic acid were the respective depressants. Bastnaesite is a primary natural source of light rare earth elements. Adequate flotation of bastnaesite, as a fluoro carbonate mineral, in the presence of various Ca-containing gangue minerals, such as calcite, is complex due to similar surface characteristics. This study aimed to develop an environmentally benign flotation reagent scheme using organic acids to enhance bastnaesite flotation while selectively depressing calcite. Systematic flotation, zeta potential, adsorption density, and X-ray photoelectron spectroscopy analyses were carried out using lactic acid (LA) and succinic acid (SA) as depressants and sodium oleate as a collector. The results of flotation and surface chemistry analyses demonstrated that organic acids preferentially adsorbed on the calcite surface, significantly reducing calcite recovery to below 20% and 10% when using lactic acid and succinic acid, respectively. The collective findings of this study demonstrate the tremendous potential of organic acids to be used as effective calcite depressants in bastnaesite flotation system. [ABSTRACT FROM AUTHOR]

• Oleate hydroxamic acid was synthesized and applied to bastnaesite flotation. • OLHA significantly increased the hydrophobicity of the bastnaesite surface. • OLHA and SHMP have competitive adsorption on the bastnaesite surface. • OLHA was interacted with bastnaesite by chemical absorption. Hydroxamic acid collectors display excellent selectivity but poor collecting ability in bastnaesite flotation. Improving the collecting capacity of hydroxamic acid collector appropriately become an effective method to enhance the performance of flotation reagents. A novel oleate hydroxamic acid (OLHA) as a collector was synthesized and applied to bastnaesite flotation in this work. The structure of OLHA was characterized by Fourier transform infrared spectrometry (FTIR) and nuclear magnetic resonance spectroscopy (NMR). The single mineral and artificial mixed minerals flotation experiments results show that OLHA achieved efficient flotation separation of bastnaesite and barite when odium hexametaphosphate (SHMP) was used as depressant. The contact angle, zeta potential, FTIR and X-ray Photoelectron Spectroscopy (XPS) measurements were performed to investigate the adsorption mechanism of OLHA. The contact angle results show that OLHA significantly improved the surface hydrophobicity of bastnaesite. Zeta potential and FTIR results show that in the presence of SHMP, OLHA selectively adsorbs to the surface of bastnaesite. Over all, OLHA adsorbs on the surface of bastnaesite through chemically adsorption, and strengthen the hydrophobicity of bastnaesite surface. Therefore, OLHA is a promising collector for bastnaesite flotation. [ABSTRACT FROM AUTHOR]

• Identified dithiocarbamate ester as efficient bastnaesite collector. • Compared HABTC, HAPTC, HAETC via flotation and CLogP calculation. • Explored HABTC adsorption on bastnaesite by Zeta Potential, FTIR, and XPS. • Unveiled a hypothesized reaction pathway: HABTC-Ce (III) complex formation. To adequately utilize the critical rare earth resource by flotation, finding effective collectors has attracted increasing attention in the mining industry. A promising collector group is dithiocarbamate ester surfactant. In this study, S-[(2-hydroxyamino)-2-oxoethyl]-N, N-dibutyl-dithiocarbamate (HABTC), S-[(2-hydroxyamino)-2-oxoethyl]-N, N-dipropyl-dithiocarbamate (HAPTC), and S-[(2-hydroxyamino)-2-oxoethyl]-N, N-diethyl-dithiocarbamate (HAETC), were employed in the flotation of bastnaesite. The flotation performance achieved using HABTC was found to be the most satisfactory, aligned with the hydrophobicity determination by CLogP. Additionally, the adsorption mechanism of HABTC towards bastnaesite surfaces was systematically evaluated. Zeta potential measurements provided evidence of a chemisorption interaction between bastnaesite and HABTC. Results obtained from FTIR and XPS analyses indicated that HABTC likely underwent a reaction with the Ce (III) atoms present on the surface of bastnaesite. This reaction was hypothesized to occur through the O and S atoms of the N-C(S), S C, and C(O) N OH groups in HABTC, leading to the formation of complexes. The universal mechanism found in this work provides considerable potential for the extensive application of HABTC within rare earth flotation. [ABSTRACT FROM AUTHOR]

Given the indispensability and immense value of rare earth elements for scientific and technological advancements in the 21st century, extracting high-quality rare earth resources from nature has become a global priority. Bastnäsite-(Ce) is one of the known rare earth minerals with high rare earth content and wide distribution, which occupies a pivotal position in human life and high-end production activities, making its efficient development and utilization crucial. In recent years, research on separating bastnäsite-(Ce) from gangue minerals has focused on the flotation process, with flotation reagents playing a critical role in achieving effective separation. This paper provides a detailed summary of current research on the behavior of bastnäsite-(Ce) flotation agents on minerals, their interaction with mineral surfaces during flotation separation, and outlines future prospects for further research. [Display omitted] • Detailed summary of the classification of bastnaesite flotation reagents according to different functions • Focus on separation from gangue minerals is a key aspect of bastnaesite recovery. • Emphasis on the flotation reagent and mineral surface interaction mechanism for a very clear summary • Explain the obvious advantages of novel flotation reagents over traditional reagents • Prospects for flotation reagents for bastnaesite rare earth ore [ABSTRACT FROM AUTHOR]

[Display omitted] • The mixed collectors improve the collecting ability and selectivity of bastnaesite comprehensively. • The BHA and SHA are chemically adsorbed by Ce site on the bastnaesite surfaces. • The two mixed collectors have a stronger adsorption ability on bastnaesite surface than single collectors. • The chelate formed of BHA and SHA on banaesite is most likely to exist in the form of the five-membered ring. Bastnaesite, as one of the most important sources of rare earth elements, are typically separated through flotation. However, the complex association and fine particle size of bastnaesite make it challenging to achieve high flotation recovery and grade. In this study, mixed collectors composed of benzohydroxamic acid (BHA) and salicyhydroxamic acid (SHA) has been developed for the flotation of bastnaesite. Results show that BHA has better collection performance while SHA show better selectivity in the flotation separation of calcite and dolomite. The combination of BHA and SHA in the flotation turn out that the recovery and grade of bastnaesite are simultaneous promoted compared to single collector. Adsorption experiments indicate that bastnaesite has larger adsorption capacity to BHA, while SHA are more selective adsorbed on bastnaesite rather than calcite and dolomite. Zeta potential measurements confirm the stronger adsorption of mixed collector onto the bastnaesite surface compare to single collectors, which agree well with the flotation results. The FTIR analyses show that the mixed collector undergoes a chemical reaction on the bastnaesite surface, facilitating chelation between the collector and bastnaesite. The XPS analyses verified that the newly formed bonds are Ce-O bonds between the collectors and bastnaesite. Overall, this study developed a kind of mixed collector for bastnaesite flotation, the synergistic effect and co-adsorption of BHA and SHA on bastnaesite surface have been demonstrated, which provide new approach to improve the flotation recovery and grade of bastnaesite. [ABSTRACT FROM AUTHOR]

[Display omitted] • OIBHA enables efficient separation of bastnaesite and calcite powders. • OIBHA can be adsorbed on bastnaesite surface. • OIBHA has a stronger matching relationship with the surface of bastnaesite. Bastnaesite is an important mineral resource, usually associated with calcite and other minerals, flotation is one of the most widely used methods in the selection process. Collector is the key to achieve flotation separation of bastnaesite from gangue mineral. The effect of a new hydroxamic acid collector with two functional groups: Octylamino-bis-(isobutanohydroxamic acid) (OIBHA), on the flotation separation of bastnaesite from calcite was investigated. The Single mineral and artificial mixed ore flotation results revealed that OIBHA exhibited better collecting ability and selectivity compared with the conventional hydroxamic acid collector octanohydroxamic acid (OHA). Effective separation between bastnaesite and calcite can be realized. The concentrate with 68.82 % REO grade and 90.23 % REO recovery was obtained with 3 × 10−4 mol/L OIBHA. Fourier transform infrared (FTIR) analysis, zeta potential measurements and quantum chemical calculations were used to investigate the selective adsorption mechanism of OIBHA. The results of FTIR analysis and zeta potential measurements showed that OIBHA was strongly adsorbed on the surface of bastnaesite, but did not interact with calcite. Quantum chemical calculations results indicated OIBHA matched well with bastnaesite surface, thereby improved the selectivity. The results in this paper are instructive for the study of the spatial matching properties of collectors and mineral surfaces. [ABSTRACT FROM AUTHOR]

The target rare earth mineral in the Dalucao REE Deposit in the Sichuan province is bastnaesite. The target mineral has fine disseminaton size and complex dissemination relationship with other minerals, and the associated minerals such as fluorite, barite, strontium and barium sulfate mineral are high content. The ore sliming is serious, which makes it difficult to recycle rare earth. Aiming target mineral' s distribution and unique characteristics, the flotation magnetic process was established. Lots of tests for the flotation technical condition were conducted in the laboratory, especially the appropriate grinding fineness and optimum flotation reagent system, such as the desliming test, the dosage and types tests for collector, inhibitor and frother. The beneficiation process of refractory rare earth ore showed that the efficient separation could be obtained under the condition of the pre desliming,at grinding fineness of 65% passing 0. 074 mm. At roughing stage, using water glass as inhibitors, new collector 103 as collector and SL 301 as frother, a closed circuit flowsheet of "pre desliming, two roughing, three scavenging, three cleaning, cleaning scavenging" was adopted. The close circuit results showed that the grade and recovery rate of REO in the rare earth flotation concentrate was 30. 38% and 73. 74% respectively, and flotation secondary concentrate was 11. 93% and 13. 41%. The final rare earth concentrate with a grade of 61. 11% and a recovery of 60.09% is obtained after the flotation concentrate passes through the "one roughing, one scavenging" high intensity magnetic separation with a magnetic field intensity of 1.19x10³kA/m. The rough concentrate and the middling produced by the flotation concentrate pass through the high intensity magnetic separation with a magnetic field intensity of 1.19x10³kA/m and then pass through the strong magnetic operation with grade of 56.03% and recovery of 3.87%. The total recovery is 63.96%. [ABSTRACT FROM AUTHOR]

Carbonatites host Earth’s main REE deposits, with bastnaesite (LREE)CO3F being the main economic REE-bearing mineral. However, bastnaesite mineralisation processes are debated between hydrothermal or magmatic origin. This study aims to assess if bastnaesite can be magmatic, and to characterise the REE behaviour during carbonatite crystallisation. Crystallisation experiments have been performed from 900 to 600 °C at 1 kbar, on a REE-rich calciocarbonatitic composition. REEbearing calcite is the dominant crystallising mineral, driving the residual melt towards natrocarbonatitic compositions. Both halogens (i.e., Cl and F) and water decrease the temperature of calcite saturation. REE are slightly incompatible with calcite: for all REE, partition coefficients between carbonate melt and calcite are comprised between 1 and 11, and increase with temperature decrease. Britholite (REE, Ca)5((Si,P)O4)3(F,OH) crystallises at high temperatures (700–900 °C), while pyrochlore (Ca,Na,REE)2Nb2O6(OH,F) crystallises at low temperatures (600–700 °C), as well as REE-rich apatite (600–650 °C). No bastnaesite is found in crystallisation experiments.We thus performed a bastnaesite saturation experiment at 600 °C. The bastnaesite-saturated melt contains 20 wt% of REE: such magmatic saturation is unlikely to happen in nature. Textural evidences imply a Na, Cl, REE-rich fluid at high temperatures and hydrous conditions.We propose that fluids are the main mineralising agent for bastnaesite at hydrothermal stage (<600 °C). [ABSTRACT FROM AUTHOR]

The paper reports major relations and trends determined in the distributions of trace elements and the Sr and Nd isotope composition of leucogranites of the Turga massif in Eastern Transbaikalia. Three varieties of the leucogranites are distinguished: porphyritic biotite granites, equigranular granites with Li-siderophyllite, and amazonite granites that make up small stocks and dikes. All of the rocks define a single Rb–Sr isochron that corresponds to an age of 134 ± 1 Ma at IR(Sr) = 0.71768 ± 22 and MSWD = 1.2, i.e., all of these rocks crystallized within a narrow age span. The porphyritic biotite granites, which are thought to be parental for the leucogranites, crystallized at lower temperatures (710–740°C) than the younger granites with Li-siderophyllite (810–850°C). Moreover, the granites with Li-siderophyllite have elevated Fe concentrations, which is reflected in that their micas are Fe-rich. The leucogranites are enriched in HFSE (270 ± 59 ppm Zr, 337 ± 93 ppm REE, 72 ± 31 ppm Th, and 16 ± 6 ppm U), which is atypical of amazonite granites in the study area. Considered together with very low Sr and low Ti and P concentrations, these compositional features are distinguishing features of A-type granites. The rare-metal granites of the Turga massif are unique in composition: being similar to amazonite granites in mineralized massifs, these rocks carry accessory minerals typical of peralkaline rocks. They contain LREE fluorides and fluorcarbonates (fluocerite, bastnaesite, and parisite), minerals of the pyrochlore and samarskite groups, and minerals of the isostructural group of REE–Y–Zr–Th–U silicate-phosphates. Our data provide grounds for classifying the rare-metal granites of the Turga massif with an unusual transitional geochemical subtype: peraluminous columbite-bearing amazonite granites of elevated alkalinity with peralkaline REE–Nb–Zr–Th–U mineralization. [ABSTRACT FROM AUTHOR]

Relaxation behavior was investigated in typical La-based bulk metallic glasses by dynamic mechanical analysis, both in the isochronal and in the isothermal routes. Two relaxations were observed: the main relaxation (α), associated with the glass transition, and a secondary relaxation, at lower temperature or higher frequency. This secondary relaxation corresponds to the well known Johari-Goldstein (JG) β relaxation. Master curves can be obtained. The activation energy Eβ of β relaxation (about 1 eV) is in agreement with the empirical relation Eβ ≈ 26(±2) RTg. The high value of the activation energy Eα of the α relaxation (about 5 eV) indicates that this relaxation corresponds to correlated movements. The mechanism of JG β relaxation in metallic glasses is discussed. [ABSTRACT FROM AUTHOR]

The hydrophobic mechanism of N -[(3-hydroxyamino)-propoxy]- N -octyl dithiocarbamate (OAHD) toward bastnaesite flotation. • N -[(3-hydroxyamino)-propoxy]- N -octyl dithiocarbamate collector was designed. • Both dithiocarbamate and hydroxamate groups had weak affinity to Ca2+ ions. • In situ AFM clearly observed that OAHD aggregated on bastnaesite surface. • OAHD's dithiocarbamate and hydroxamate groups co-anchored on bastnaesite. • OAHD returned a selective flotation separation of bastnaesite from calcite. Both hydroxamate and dithiocarbamate groups exhibit a unique bonding characteristic toward rare earth ions. A hydroxamic acid surfactant containing a dithiocarbamate group should possess a specific affinity to hydrophobize bastnaesite [(Ce, La)CO 3 F] flotation. N -[(3-hydroxyamino)-propoxy]- N -octyl dithiocarbamate (OAHD) was synthesized, and its flotation mechanism toward bastnaesite was investigated by in situ AFM, FTIR, XPS, micro-flotation and contact angle. In situ AFM clearly observed that OAHD aggregated on bastnaesite surface, which improved the contact angle and surface hydrophobicity of bastnaesite. FTIR spectra and XPS recommended that OAHD's dithiocarbamate and hydroxamate groups co-anchored on bastnaesite surface through strong chemisorption, which strengthened the bonding affinity of bastnaesite toward OAHD. UV spectra showed that both dithiocarbamate and hydroxamate groups exhibited weak affinity toward Ca2+ ions, which benefited OAHD's selective flotation separation of bastnaesite from calcite. The co-adsorption and special hydrophobic structure improved OAHD's flotation performance. As a result, OAHD returned higher flotation selectivity for bastnaesite than OHA (n -octyl hydroxamic acid) which chemisorbed on bastnaesite surface only through the hydroxamate group and used the heptyl as hydrophobic group. [ABSTRACT FROM AUTHOR]

Bastnaesite (Ce0.50La0.25Nd0.20Pr0.05)CO3F is an interesting pattern family of (CO3)2− and F− co-existing phases, which is a meaningful sample to study the influence of multiple volatiles on minerals. Thermal stability of bastnaesite has been investigated by thermogravimetric experiment and in situ high-temperature Raman. The results demonstrate that bastnaesite undergoes a decarbonization transition at above 673 K. The isobaric-mode Grüneisen parameters range from 0.04 to 2.28. The compressibility of bastnaesite has been investigated by synchrotron radiation X-ray diffraction and Raman spectroscopy combined with diamond anvil cells up to 19.2 GPa at room temperature. Isothermal pressure–volume relationship of bastnaesite is fitted to the second-order Birch–Murnaghan equation of state with V0 = 430.87(3) Å3, K0 = 118.35(1) GPa. Its axial compressibility presents anisotropic, attributed to the rigid (CO3)2− group parallel to c-axis. Its isothermal-mode Grüneisen parameters and intrinsic anharmonic-mode parameters range from 0.23 to 1.91 and− 3.5 × 10−5 K−1 to 0.82 × 10−5 K−1, respectively. The presence of F− can largely enhance the thermal stability and incompressibility of minerals. [ABSTRACT FROM AUTHOR]

One of the most important aspects in any flotation separation is the choice of the flotation collector. For this reason, based on both our recent research developments and the results from other researchers, this detailed review focuses on fundamental surface chemistry features of fatty acid, hydroxamate, phosphonate, and phosphate as collectors for the flotation recovery of the rare earth (RE) mineral, bastnaesite, including selectivity considerations with respect to separation from calcite, barite, and quartz. [ABSTRACT FROM AUTHOR]

The dielectric relaxation at temperatures ranging from 100 °C to 550 °C in lanthanum-doped barium strontium titanate glass ceramics has been investigated by measurements of both dielectric temperature curve and complex impedance spectroscopy. The temperature dependence of dielectric properties reveals two regimes. In the first regime, at temperatures lower than 350 °C, the charge carrier contributed to interfacial polarization is conduction electrons. In contrast, in the second regime, at temperatures higher than 350 °C, the dielectric relaxation was attributed to the thermally activated movement of oxygen vacancies. Thus, two relaxation mechanisms could be explained on the basis of defect chemistry and impedance analysis. [ABSTRACT FROM AUTHOR]

• Dextrin hydrate has depressant effect on flotation separation of bastnaesite from monazite. • Dextrin hydrate is adsorbed on monazite surface by hydroxyl. • A possible adsorption mechanism and adsorption mode is proposed. The flotation separation of bastnaesite and monazite is challenging due to their similar physicochemical properties and floatability. In this work, an environmentally friendly depressant, dextrin hydrate (DH), was introduced for the flotation separation of bastnaesite from monazite using caprylhydroxamic acid (CHA) as the collector. The flotation behavior of bastnaesite and monazite in the absence and presence of DH was studied by micro-flotation tests. The mechanism was investigated by Zeta potential, Fourier infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The flotation results showed that monazite recovery decreased by 68.47% when the pH was 9.0 ± 0.2 and the amount of DH was 2.2 mg/L. In contrast, the bastnaesite recovery only exhibited a slight reduction of 7.98% under these conditions. Zeta potential analysis showed that DH had a strong effect on the subsequent adsorption of CHA on the surface of monazite but a minor effect on bastnaesite. FTIR and XPS analysis further confirmed that the chemisorption of DH on the Ce sites of monazite occurred. For bastnaesite, the adsorption of CHA still could be detected, making the bastnaesite well floatable. Therefore, the efficient separation of bastnaesite from monazite could be achieved with the DH as a selective depressant. [ABSTRACT FROM AUTHOR]

The agglomeration of bastnaesite and fine fluorite severely reduces the recovery of bastnaesite, and a method to address this issue is urgently needed. Using measurement techniques such as micro-flotation, contact angle, zeta potential, in situ attenuated total reflectance-Fourier transform infrared (In situ ATR-FTIR) spectroscopy, and extended theory for calculating the stability of solution colloid (E-DLVO theory), this study investigated the selective adsorption mechanism of sodium hexametaphosphate (SHMP). The flotation results indicated that when sodium oleate (NaOL) was used as the collector, SHMP was 2.5 × 10−6 M, showing an outstanding flotation separation of bastnaesite from fine fluorite. The contact angle and zeta potential results showed that SHMP selectively increased the surface hydrophobicity and decreased the surface potential of fluorite. Additionally, in situ ATR-FTIR spectroscopy measurements revealed that HPO 4 2- and H 2 PO 4 - of SHMP chemically reacted with Ca2+ ions on the surface of fluorite and finally formed CaHPO 4 and Ca(H 2 PO 4) 2 stable complexes. However, SHMP was adsorbed by bastnaesite. Furthermore, EDLVO theoretical calculations confirmed that with the addition of SHMP, the electrostatic attraction of the double electric layer between the particles weakened 10 times, hydration repulsion was intense, and the total force between the particles changed from attractive to repulsive. The results also showed that fluorite and bastnaesite dispersed each other. Thus, SHMP can be used as a high-performance selective depressant for the fluorite flotation to realize bastnaesite flotation. [Display omitted] [ABSTRACT FROM AUTHOR]

Well-ordered large-area arrays of ferroelectric La-substituted Bi4Ti3O12 (BLT) nanostructures were prepared by pulsed laser deposition using gold nanotube membranes as shadow masks. By x-ray diffraction and transmission electron microscopy, it was found that well-defined (001)-, (118)/(100)-, and (104)-oriented BLT nanostructures were obtained on (001)-, (011)-, and (111)-oriented SrTiO3 single crystal substrates covered with epitaxial SrRuO3 electrode layers, respectively, through ex situ crystallization at 700 °C. Atomic force microscopy analyses revealed that the epitaxial BLT nanostructures maintain a height of about 100 nm and a lateral size of about 150 nm in spite of the postannealing process. The anisotropic ferroelectric properties of the BLT nanostructures of three different orientations were investigated by scanning force microscopy in piezoresponse mode. The highest effective remanent piezoresponse coefficient (2dzz) of about 38.0 pm/V was observed in (118)/(100)-oriented BLT nanostructures, whereas (001)- and (104)-oriented nanostructures showed smaller 2dzz values of 5.0 pm/V and 1.4 pm/V, respectively. [ABSTRACT FROM AUTHOR]

This paper reports on the results of studies of the carbonate–fluoride isolations with extremely high Y and REE concentrations from biotite–arfvedsonite granite of the Katugin rare metal deposit. We obtained the chemical data on that minerals that compose these isolations—gagarinite-(Y), tveitite-(Y), fluocerite-(Ce), bastnaesite, and fluornatropyrochlore. A carbonate–fluoride globule with a well-preserved crystallization order was revealed in quartz of the host granite. This finding might be evidence of silicate–fluorine immiscibility suggested before for the Y–REE isolations in the Katugin granites. We assumed that the fluoride melt occurred at the magmatic stage of the formation of biotite–arfvedsonite granite, which resulted in depletion of the host granite with fluorine and the redistribution of the REE and Y in the fluoride salt melt. [ABSTRACT FROM AUTHOR]

• The mechanochemical decomposition on bastnaesite concentrate is studied. • At first, breakage from balls to particles plays an important role. • With progressive decomposition, product layer develops. • Fluorine washing efficiency reaches 97.6% using 56% NaOH with liquid-solid 0.8:1. In the paper, mechanochemical decomposition (a combine of mechanical milling and chemical decomposition) on bastnaesite concentrate with NaOH solution was studied. Particle size, BET specific surface area and pore volume were measured to study the structural developments of decomposition residue containing activated bastnaesite and decomposition product RE(OH) 3. X-ray diffraction analysis and SEM-EDS were used to investigate the microstructural changes. The results showed that at the early stage, breakage from balls to particles played an important role. The particle size in initial bastnaesite decreased rapidly from 125 μm to 7.25 μm and specific surface area increased remarkably from 0.04 m2/g to 7.33 m2/g in the first 5 min. The bastnaesite particles with fresh surface could directly react with NaOH, and increase in amorphization degree obviously improved reactivity of bastnaesite. At the later stage, with progressive decomposition, the thickness of product layer increased and the structure became dense with decrease in the pore volume from 0.031 cm3/g to 0.024 cm3/g. In addition, this is accompanied with increase in the crystallinity degree and crystallite size as well as decrease in the microstrain. Thus, the decomposition of bastnaesite can be enhanced. Washing efficiency of fluorine reached 97.6% at 180 °C using 56% of NaOH concentrate with 0.8:1 of liquid-solid for 180 min. Finally, the change of fluorine washing efficiency with time further verified the result that the reaction controlling step had a transformation from chemical reaction to diffusion control through product layer. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The effect of EDTA on the separation of bastnaesite from fluorite by flotation was investigated. • Fluorite can be selectively depressed in bastnaesite flotation by EDTA. • Chemically adsorbed OHA on fluorite can be dissolved into soluble metal-EDTA complexes. • Chemically adsorbed OHA on bastnaesite is still stable after the addition of EDTA. Abstract Bastnäsite is an important mineral resource in the production of rare earth materials and is usually beneficiated by flotation. The flotation of bastnäsite is problematic due to the competitive adsorption of hydroxamate collector on bastnäsite and its associated calcium-bearing gangue minerals such as fluorite. One strategy to solve this problem is to use effective depressants to depress the gangue minerals. However, the current depressants all have some drawbacks. In this study, the effect of ethylenediamine tetraacetic acid (EDTA) as a depressant was tested in the flotation of single mineral of bastnäsite and fluorite and their mixture. The mechanism underpinning the role of EDTA was investigated through theoretical thermodynamic calculation, zeta potential and X-ray photoelectron spectroscopy (XPS) measurements. The results show that fluorite was significantly depressed, while the flotation of bastnäsite was almost unaffected when EDTA was present. The separation index between bastnäsite and fluorite increased from 1.18 to 12.66 with the increase of EDTA concentration from 0 to 7.79 kg/t. It was found that EDTA could dissolve the chemically adsorbed octyl hydroxamic acid (OHA) on fluorite through the formation of soluble Ca-EDTA complexes, whereas the chemically adsorbed OHA on bastnäsite was more stable and could not be transformed into Ce-EDTA spontaneously. Therefore, the flotation of fluorite was selectively depressed by EDTA. The results show that EDTA was a promising depressant for fluorite gangue mineral in bastnäsite flotation. [ABSTRACT FROM AUTHOR]

Abstract Cerium oxide (IV) hollow nanospheres (@CeO 2) were successfully synthesized via the hydrothermal method. Cerium nitrate and urea were used as a ceria precursor and as a hydrolyzing agent, respectively. Obtained @CeO 2 nanospheres were characterized using TEM, N 2 physisorption, XRD, UV–Vis and Raman spectroscopy. The structural properties of @CeO 2 nanospheres have been tuned by a variation of the urea/cerium nitrate weight ratio during the synthesis. The adsorption capacity of @CeO 2 nanospheres was shown to be related to the size of ceria crystals forming nanospheres. Thus, the decrease of ceria crystal size permits to improve the efficiency in the adsorption of toxic 4-nitrophenol. Graphical abstract Image 1 Highlights • @CeO 2 hollow nanospheres with a tunable structure were synthesized. • The size of CeO 2 crystals decreased with the urea content increase under the synthesis. • 4-nitrophenol adsorption capacity is high for @CeO 2 with small ceria domain size. • The force of interaction 4-nitrophenol - @CeO 2 increased with ceria size decrease. [ABSTRACT FROM AUTHOR]

Abstract Two lanthanum manganite perovskite-nanostructures, namely; La x Ca (1-x) MnO 3 and La x Sr (1-x) MnO 3 (x = 0.1, 0.3, 0.5 and 1.0), were synthesized by hydrothermal method. To follow up the composition of formed phases, the synthesized powders were calcined at different temperatures. The obtained materials were investigated by X-ray diffraction (XRD) and transmission electron microscope (TEM). Moreover, the calcined powders were pressed at 100 MPa and sintered at variable temperatures; i.e. 1250, 1300, 1350 and 1450 °C. The phase composition and microstructural characteristics of sintered pervoskites were examined by XRD and scanning electron microscope (SEM). Furthermore, physical (bulk density and apparent porosity), electrical resistivity and magnetic properties were also determined. The results revealed that La x Ca (1-x) MnO 3 and La x Sr (1-x) MnO 3 nanostructures were successfully prepared by hydrothermal method. The physical properties of sintered pervoskites were strongly depended on dopant type and concentration. The maximum sintering temperature for La x Ca (1-x) MnO 3 was 1400 °C while for La x Sr (1-x) MnO 3 was 1450 °C, after which the materials have been fused. Materials doped with Ca or Sr exhibited lower resistivity. On the other side, the magnetic properties have been also improved after addition of Ca or Sr. This has been discussed based on the double exchange mechanism. La x Sr 1-x MnO 3 exhibited better magnetic properties than La x Ca 1-x MnO 3 and LaMnO 3. La 0.5 Ca 0.5 MnO 3 and La 0.5 Sr 0.5 MnO 3 exhibited the highest magnetization among the other pervoskites. [ABSTRACT FROM AUTHOR]

Rare Earth Elements are a group of chemical elements that include all elements of the group of lanthanides, in addition to yttrium and scandium. Due to their chemical and physical properties, Rare Earth Elements play an essential role in the high-tech product industry, making the availability of these elements extremely important for technological advancement, directly linked to the country's economy. Rare Earth Elements are found in several minerals, mainly monazite, bastnasite, xenotime and ionic adsorption clays. Due to the occurrence of the phenomenon of lanthanide contraction, the Rare Earths have great chemical and physical similarity, resulting in the difficulty of separating and obtaining the lanthanide elements in the individual form. One of the great challenges of the production chain of Rare Earth Elements is the search for new methods of extraction economically viable without harm to the environment. This bibliographical review intends to approach the mineralogical and chemical aspects of different minerals bearing Rare Earth Elements and to discuss the technological challenges in the extraction processes of these elements, focusing on the use of green technologies to compose the production chain of Rare Earth Elements. [ABSTRACT FROM AUTHOR]

A two-step synthetic route using RE(OH)CO3 colloid spheres as the sacrificial template was designed to prepare monodisperse, pure bastnasite (RECO3F: RE = Ce, La, Pr, Nd) with a hole structure for the first time. A variety of morphologies, including jujube core-like, stacked nanoblocks, and stacked nanosheets were obtained through changing the ratio of reactants. The phase, structure, shapes, and photoluminescence properties of samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. The CeCO3F:Ln3+ (Ln = Tb, Eu, Dy) phosphors give green, yellow and blue emission, respectively, due to the f–f transitions of Ln3+ ions. Furthermore, the energy transfer from Ce3+ to Dy3+ and Tb3+ was described in detail. [ABSTRACT FROM AUTHOR]