Effectively separating bastnaesite from calcium-bearing gangue minerals(particularly calcite)presents a formidable challenge,making the development of efficient collectors crucial.To achieve this,we have designed and ...Effectively separating bastnaesite from calcium-bearing gangue minerals(particularly calcite)presents a formidable challenge,making the development of efficient collectors crucial.To achieve this,we have designed and synthesized a novel,highly efficient,water-soluble cationic collector,N-dodecylisopropanolamine(NDIA),for use in the bastnaesite-calcite flotation process.Density functional theory(DFT)calculations identified the amine nitrogen atom in NDIA as the site most susceptible to electrophilic attack and electron loss.By introducing an OH group into the traditional collector dodecylamine(DDA)structure,NDIA provided additional adsorption sites,enabling synergistic adsorption on the surface of bastnaesite,thereby significantly enhancing both the floatability and selectivity of these minerals.The recovery of bastnaesite was 76.02%,while the calcite was 1.26%.The NDIA markedly affected the zeta potential of bastnaesite,while its impact on calcite was relatively minor.Detailed Fourier-transform infrared spectroscopy(FTIR)and X-ray photoelectron spectroscopy(XPS)results elucidated that the―NH―and―OH groups in NDIA anchored onto the bastnaesite surface through robust electrostatic and hydrogen bonding interactions,thereby enhancing bastnaesite's affinity for NDIA.Furthermore,in situ atomic force microscopy(AFM)provided conclusive evidence of NDIA aggregation on the bastnaesite surface,improving contact angle and hydrophobicity,and significantly boosting the flotation recovery of bastnaesite.展开更多
Rare earth elements have been widely applied in various sectors.Bastnaesite and monazite are crucial rare earth minerals,and flotation is a vital technique for recovering fine-grained rare earth minerals and separatin...Rare earth elements have been widely applied in various sectors.Bastnaesite and monazite are crucial rare earth minerals,and flotation is a vital technique for recovering fine-grained rare earth minerals and separating them from associated gangue minerals such as fluorite and apatite.Flotation collectors play a key role in selectively adsorbing valuable minerals,enhancing their surface hydrophobicity,which has prompted considerable research interest.However,the interaction between minerals and reagents relies on the reactivity and selectivity of the reagent groups,as well as the reactive properties of the surface atoms of the minerals.This study proposes the use of H_(2)O_(2)oxidation to enhance the flotation process of rare earth minerals.The flotation experiments demonstrated that pre-adding H_(2)O_(2)before introducing the flotation collector significantly improved the grade and recovery of rare earth concentrates.The adsorption mechanisms of 2-hydroxy-3-naphthyl hydroxamic acid collector on rare earth mineral surfaces before and after H_(2)O_(2)pre-oxidation were studied.The 2-hydroxy-3-naphthyl hydroxamic acid interacts with Ce^(3+)on the surface of unoxidized rare earth minerals,forming chelate compounds with five-membered ring structures.The H_(2)O_(2)exhibited potent oxidizing properties and oxidized the Ce^(3+)on the bastnaesite and monazite surfaces to more stable Ce^(4+),which demonstrated stronger binding capability with hydroxamic acid.展开更多
Sulfuric acid leaching process was applied to extracting rare earth（RE） from roasted ore of Dechang bastnaesite in Sichuan,China.The effect of particle size,stirring speed,sulfuric acid concentration and leaching te...Sulfuric acid leaching process was applied to extracting rare earth（RE） from roasted ore of Dechang bastnaesite in Sichuan,China.The effect of particle size,stirring speed,sulfuric acid concentration and leaching temperature on RE extraction efficiency was investigated,and the leaching kinetics of RE was analyzed.Under selected leaching conditions,including particle size（0.074-0.100 mm）,sulfuric acid concentration 1.50 mol/L,mass ratio of liquid to solid 8 and stirring speed 500 r/min,the leaching kinetics analysis shows that the reaction rate of leaching process is controlled by diffusion through the product/ash layer which can be described by the shrinking-core model,and the calculated activation energy of 9.977 kJ/mol is characteristic for a diffusion-controlled process.展开更多
The leaching kinetics of bastnaesite concentrate in HCl solution was investigated with respect to the effects of HCl concentration by changing HCl concentration,leaching temperature,liquid to solid ratio,and particle ...The leaching kinetics of bastnaesite concentrate in HCl solution was investigated with respect to the effects of HCl concentration by changing HCl concentration,leaching temperature,liquid to solid ratio,and particle size.A particle size of 25 μm was required to leach 89.6% RE2（CO3）3 and 1.5%REF3 at 90 ℃ for 90 min,when HCl concentration was 6 mol/L and liquid to solid ratio was 15：1.The leaching kinetics of bastnaesite concentrate is represented by shrinking core model with diffusion through a porous product layer.The activation energies for the dissolution reaction of RE2（CO3）3 and REF3 were calculated to be 59.39 kJ/mol and 66.13 kJ/mol respectively.展开更多
Rare earth element is an important strategic metal,but the supply of high purity rare earth ores is growing slowly,which is in sharp contradiction with the rapidly growing demand.Froth flotation has been confirmed to ...Rare earth element is an important strategic metal,but the supply of high purity rare earth ores is growing slowly,which is in sharp contradiction with the rapidly growing demand.Froth flotation has been confirmed to be an effective method to separate bastnaesite from its gangue minerls.However,the traditional collectors are facing serious problems in flotation separation of minerals,requiring the addition of excess depressant and regulator in the flotation process.Herein,we proposed and synthesized novel Gemini hydroxamic acids Octyl-bishydroxamic acid(OTBHA),Decyl-bishydroxamic acid(DCBHA)and Dodecyl-bishydroxamic acid(DDBHA)as the collectors in bastnaesite-barite flotation system.The effect of different carbon chain lengths on the molecular properties were explored by density functional theory(DFT)calculations.DCBHA possessed a stronger reactivity compared with OCBHA and DDBHA.The flotation results verified the consistency of the computational calculation about the performance prediction of Gemini hydroxamic acids.Compared with OCBHA and DDBHA,DCBHA displayed superior collecting affinity toward bastnaesite,and did not float barite.Zeta potential results showed that the presence of DCBHA increased the potential of bastnaesite,while it had almost no effect on barite,indicating DCBHA had a stronger affinity for bastnaesite.Then,Fourier transform infrared(FTIR)and X-ray photoelectron spectroscopy(XPS)analyses indicated that the adsorption mechanism was due to two hydroxamate groups of DCBHA co-anchored on bastnaesite surface by forming five-membered hydroxamic―(O―O)―Ce complexes.In addition,atomic force microscopy(AFM)clearly observed that DCBHA uniformly aggregated on bastnaesite surface,which increased surface contact angle and improved the hydrophobicity of bastnaesite.展开更多
A bastnaesite crystal about 12×20 mm 2 in size collected from a pegmatitic aegirine augite barite bastnaesite vein of the Maoniuping rare earth deposit, Mianning County, Sichuan Province, has been analyzed for...A bastnaesite crystal about 12×20 mm 2 in size collected from a pegmatitic aegirine augite barite bastnaesite vein of the Maoniuping rare earth deposit, Mianning County, Sichuan Province, has been analyzed for La, Ce, Pr and Nd by synchronous radiative X ray fluorescence(SRXRF) technics at the National BEPC Laboratory. The results show an apparent compositional variation along vertical and horizontal sections accross the crystal which may be divided into three compositional zones(A, B and C). Significant difference exists between the inner portion(zone A), averaging at 28 35% La 2O 3, 35 04% CeO 2, 2 01% Pr 6O 11 and 5 44% Nd 2O 3, and the outer portion(zone B), averaging at 32 81% La 2O 3, 42 26% CeO 2 3 30% Pr 6O 11 and 7 08%. Nd 2O 3, of the crystal. Only one analysis is available on the egde of the crystal(zone C) yielding 14 50% La 2O 3, 21 41% CeO 2, 4 19% Pr 6O 11 and 16 71% Nd 2O 3, which demonstrates probably fractionations between LREE and HREE. The La/Ce ratio, however, is nearly constant around 0 84±0 08 among the three zones, while the La/Pr and La/Nd ratios erratically fluctuate due to low and variable contents of Pr and Nd. These results indicate that the REE bearing hydrothermal system underwent a significant compositional change during the stepwise growth of the bastnaesite crystal.展开更多
The flotation behaviour and mechanism of bastnaesite with N-hydroxyl phthalicimide were investigated by ξ-potential measurement,infrared spectrum and quantum chemistry calculation.The results show that 3 oxygen atoms...The flotation behaviour and mechanism of bastnaesite with N-hydroxyl phthalicimide were investigated by ξ-potential measurement,infrared spectrum and quantum chemistry calculation.The results show that 3 oxygen atoms from N-hydroxyl phthalicirnide chelate the rare earth ions on the surface of bastnaesite to form double five-chain O=C-N-O- RE(Ⅲ)-O chelate which is chemically adsorbed on the surface of bastnasite,thus making N-hydroxyl phthalicimide an effective collector for bastnaesite.展开更多
Vapor phase extraction and mutual separation of rare earth (RE) elements from bastnaesite concentrate were investigated using stepwise chlorination chemical vapor transport reactions mediated by vapor complexes LnAl ...Vapor phase extraction and mutual separation of rare earth (RE) elements from bastnaesite concentrate were investigated using stepwise chlorination chemical vapor transport reactions mediated by vapor complexes LnAl n Cl 3 n +3 (Ln=RE elements). The bastnaesite was heated to 800 K and chlorinated between 800～1300 K with C+Cl 2+SiCl 4 to remove CO 2, SiF 4 and high volatile chlorides. At the temperature of 1300 K for 6 h, the resulted RE chlorides were chemically transported and mutual separated with the vapor complexes while CaCl 2 and BaCl 2 were remained in the residues. Significantly different CVT characteristics were observed for gradually decreased and wave form temperature gradients.展开更多
The content of REE(La.Ce.Pr.Nd.Sm) in bastnaesite was measured by synchrotron radiation X-ray fluorescence microprobe.Scanning analysis makes use of excitation of the REE K lines between 33 and 50 keV.SR white beam fr...The content of REE(La.Ce.Pr.Nd.Sm) in bastnaesite was measured by synchrotron radiation X-ray fluorescence microprobe.Scanning analysis makes use of excitation of the REE K lines between 33 and 50 keV.SR white beam from a Wiggler source at the Beijing Electron Positron Collider(BEPC) of the National Laboratory,in order to excite the REE.The bastnaesite from the same mineral area was powdered to particle size≤300 mesh.It was then divided into two parts.One portion was used to be determined by XRF after depositing with oxalate and transforming into oxide.The other was pressed into disk without any binder as the reference sample.The weight and the diamieter of the disk were 15 g and 26 mm respectively.展开更多
To explore the spontaneous magnetization of iron-bearing rare earth ores during suspension roasting,binary minerals containing hematite and bastnaesite were used to investigate the effects of the roasting temperature,...To explore the spontaneous magnetization of iron-bearing rare earth ores during suspension roasting,binary minerals containing hematite and bastnaesite were used to investigate the effects of the roasting temperature,roasting time,and bastnaesite-to-hematite mass ratio on in-situ reduction of hematite in a N_(2) atmosphere.Relevant analytical tests were used to explore the mineral phase evolution during roasting,the magnetism and microstructure of the roasted products,the phase composition,and the surface element valence of concentrate.It was found that magnetic separation of the iron concentrate afforded an iron grade of 68.87% and a recovery of 93.18% under the optimum roasting conditions.During roasting,bastnaesite decomposed to generate CO_(2) and CO,and the compact structure of hematite was gradually destroyed,resulting in microcracks.Subsequently,the CO entered the surface of the hematite through the microcracks and reacted to form a magnetite shell,and the magnetite-encapsulated hematite particles were recovered via low-intensity magnetic separation.展开更多
Bastnaesite((Ce,La,Pr,Nd)CO_(3)F) is a significant light rare earth mineral found in nature,known for its fine-grained properties.Flotation is commonly employed for the recovery of fine-grained bastnaesite particles.C...Bastnaesite((Ce,La,Pr,Nd)CO_(3)F) is a significant light rare earth mineral found in nature,known for its fine-grained properties.Flotation is commonly employed for the recovery of fine-grained bastnaesite particles.Collectors serve as an essential flotation reagent that enhance the surface hydrophobicity of target minerals.A novel collector,N-hydroxy-9-octadecenamide(N-OH-9-ODA),was synthesised in this study.N-OH-9-ODA exhibits superior selectivity compared to the traditional collector oleic acid in the flotation separation of bastnaesite and fluorite.The experimental and co mputational results indicate that N-OH-9-ODA exhibits superior selectivity due to its higher adsorption affinity for bastnaesite surface compared to fluorite surface.The zeta potential and the binding energies of the Ce 3d peaks in the X-ray photoelectron spectrum(XPS) of bastnaesite surface exhibit significant shifts.Conversely,fluorite surface demonstrates minimal alterations in its zeta potential and the binding energies of the Ca 2p peaks in its XPS after its interaction with N-OH-9-ODA.展开更多
To investigate the thermal decomposition behavior and reaction kinetics of bastnaesite in suspension roasting,the gas and solid products of bastnaesite roasted in N2 and air atmospheres were examined using a gas analy...To investigate the thermal decomposition behavior and reaction kinetics of bastnaesite in suspension roasting,the gas and solid products of bastnaesite roasted in N2 and air atmospheres were examined using a gas analyzer,X-ray diffraction(XRD),scanning electron microscopy(SEM),and energy dispersive spectrometry(EDS).Subsequently,the kinetic parameters of bastnaesite in the suspension roasting process were derived and calculated using the isothermal method.The results show that the decomposition product of bastnaesite in N_(2) is CeOF.However,once the roasting temperature exceeds 600℃,CO is generated in addition to CO_(2),and all the XRD diffraction peaks of CeOF are shifted to the right,indicating that CO_(2) can oxidize CeOF and lead to the transformation of Ce(Ⅲ) into Ce(Ⅳ).When roasted in air,the decomposition product CeOF can be completely converted to CeF3 and Ce_(7)O_(12) as it easily oxidizes.Additionally,the reaction rate of bastnaesite in air is higher than that of N_(2),and the starting reaction temperature is lower than that of N_(2).A large number of irregular cracks and holes appear on the surface of solid-phase products following suspension roasting,which are due to the thermal decomposition of bastnaesite that produces CO_(2) as well as the reconstruction of the lattice of the solid-phase products.The reaction kinetic model of bastnaesite roasted in N_(2)(temperature range 600-750℃) and air(temperatu re range 500-575℃) confo rms to the A_(3/2) model with the mechanism function G(α)=-ln(1-α)^(2/3),and the reaction activation energy is 59.78 kj/mol and lnA is 1.65 s^(-1) in N_(2) atmosphere.In air,the reaction activation energy is 100.30 kj/mol and lnA is 9.63 s^(-1).展开更多
The separation of rare earths is difficult due to their similar properties and the complex characteristics of associated vein o res.Complexation-ultrafiltration(CUF)and shear induced o rderly dissociation coupling wit...The separation of rare earths is difficult due to their similar properties and the complex characteristics of associated vein o res.Complexation-ultrafiltration(CUF)and shear induced o rderly dissociation coupling with ultrafiltration(SIODUF)were used to separate metal ions(M,M=La(Ⅲ),Ce(Ⅳ)and Ca(Ⅱ))from simulated bastnaesite leaching solution using acidic phosphonic chitosan(aPCS)and rotating disk membrane.Effect of simultaneous removal of metallic ions was investigated by CUF,and suitable conditions were obtained for C/M 10.0(mass ratio of complexant to metal ions)and pH 5.0.The shear stabilities of aPCS-M complexes were explored at different pH values and the results show that the complexes can dissociate at a certain rotational speed,the critical one.The critical s hear rates of aPCS-La,aPCS-Ce and aPCS-Ca complexes at pH 5.0 were calculated as 1.42×10^(5).1.69×10^(5) and 9.75×10^(4) s^(-1),respectively.The order of complexes shear stability is aPCS-Ca aPCS-La<aPCS-Ce.The high selective separation of M and regeneration of aPCS were achieved by SIODUF in the light of the difference of aPCSM complexes shear stabilities.The separation coefficientsβLa/Ce andβCa/La reach 31.2 and 53.9,respectively.展开更多
To clearly elucidate the oxidative roasting behaviors of the bastnaesite, the thermal decomposition and oxidation of the bastnaesite concentrate in inert and oxidative atmosphere have been investigated in detail. Expe...To clearly elucidate the oxidative roasting behaviors of the bastnaesite, the thermal decomposition and oxidation of the bastnaesite concentrate in inert and oxidative atmosphere have been investigated in detail. Experimental data indicated that the initial decomposition temperature of the concentrate under N2 atmosphere is 150 ℃ higher than that under O2 atmosphere,most likely because the oxidation of the cerium induces the decomposition of the concentrate. For the roasted samples under N2 atmosphere at500 ℃ and above,the oxidation efficiency of the cerium is 19.8%-26.8% because of the fact that rareearth fluorocarbonate is first decomposed to form rare-earth oxyfluoride and CO2, and the cerium oxyfluoride is then partially oxidized by the CO2 gas. The rest cerium in these samples can be further oxidized in air at room temperature, with the oxidation efficiency of the cerium gradually increasing to above 80% in 7 d. This can be attributed to the obvious changes in the inner morphology of the roasted samples under N2 atmosphere at high temperatures, which largely induce the diffusion of the air and improves the oxidation activity of CeOF, and further induces the oxidation of CeOF by the air. XRD and XPS techniques were used to further verify the significant differences in the thermal decomposition behaviors of the bastnaesite concentrate under N2 and O2 atmosphere. Moreover, no oxidation of Pr^（3＋） to Pr^（4＋） in the roasted samples under both N2 and O2 atmosphere is observed. This gives an overall understanding of the oxidative roasting of the bastnaesite concentrate without additives.展开更多
To understand the flotation mechanism of bastnaesite using reactive oily bubble, the interaction between bastnaesite parti-cles and reactive oily bubbles was investigated by electro-kinetic studies, induction time mea...To understand the flotation mechanism of bastnaesite using reactive oily bubble, the interaction between bastnaesite parti-cles and reactive oily bubbles was investigated by electro-kinetic studies, induction time measurements and small-scale flotation ex-periments. The bastnaesite flotation could be seen as a hetero-coagulation between bastnaesite particles and reactive oily bubbles which was confirmed by the zeta potential distribution and induction time measurements from pH 4.8 to pH 9.0. The small-scale flotation tests were consistent with the hetero-coagulation results, and showed a better flotation of reactive oily bubble than air bubble among all pH range. The interaction force between bastnaesite particles and reactive oily bubbles was evaluated by the classical DLVO theory. It indicated that the attachment could be predicted well by the DLVO theory only in a restricted pH range due to the absence of hydrophilic interaction repulsion force and chemical interaction force.展开更多
Extracting rare earths from bastnaesite concentrate treated by calcification transition was studied through the single factor test and XRD patterns of bastnaesite after calcification and slags after leaching in HCl so...Extracting rare earths from bastnaesite concentrate treated by calcification transition was studied through the single factor test and XRD patterns of bastnaesite after calcification and slags after leaching in HCl solution. And the effects of the main calcified parameters such as temperature, liquid/solid and calcified time on transition performance of bastnaesite were investigated. It was found that under the optimal conditions of calcification temperature of 250 oC, liquid/solid of 20 mL/g, calcification time of 180 min, the highest leaching rate of rare earth were obtained, with the leaching ratio of rare earths 83.70% and Ce 77.01%, La 90.55%, Nd 92.03%, respectively; loss rates of fluorine with different calcification conditions were always less than 1% and XRD patterns of calcification slags and leaching slags showed that fluorine existed in the form of CaF2.展开更多
The structural and electronic properties of bastnaesite were studied by using the first-principles method based on the density functional theory(DFT).The geometry structure of bastnaesite was first optimized,and then ...The structural and electronic properties of bastnaesite were studied by using the first-principles method based on the density functional theory(DFT).The geometry structure of bastnaesite was first optimized,and then the Mulliken populations,electron density and density of states were calculated and further analyzed in detail.The calculation results reveal that it mainly ruptures along the ionic Ce-O and Ce-F bonds during the cleavage of bastnaesite,leaving≡Ce^+,≡F^-and≡CO3^-dangling bonds exposed on the cleavage surface of bastnaesite.Combined with contact angle measurement,surface complexation theory and XPS analysis,the implications of structural and electronic properties on bastnaesite flotation reactions were studied.The hydration of exposed strong ionic bond on cleavage surface results in hydrophilic surface.According to surface complexation theory,the formed surface groups are≡CeOH^0,≡CO3 H^0 and≡FH^0 groups.The investigated metal ions and flotation reagents complex with surface≡CeOH^0 groups,while≡CO3H^0 and≡FH^0 groups are not involved in the complexation.The high activity of Ce atoms facilitates these surface reactions.展开更多
Bastnaesite is an important rare earth mineral and is usually beneficiated by flotation.Sodium silicate is commonly used to depress calcium-bearing gangue minerals,however it can also depress bastnaesite when Ca^(2+) ...Bastnaesite is an important rare earth mineral and is usually beneficiated by flotation.Sodium silicate is commonly used to depress calcium-bearing gangue minerals,however it can also depress bastnaesite when Ca^(2+) ions exist in the pulp.In this study,the effect of Ca^(2+) ions and sodium silicate individually or in combination on bastnaesite flotation was studied through micro-flotation,zeta potential,fluorescence spectroscopy and X-ray photoelectron spectroscopy(XPS) measurements.Micro-flotation results show that the combination of Ca^(2+) ions and sodium silicate depresses bastnaesite more severely due to their synergistic effect.Zeta potential results show that the combination renders the surface potential of bastnaesite negatively shifted more significantly.Fluorescence spectroscopy shows that the combination decreases the surface hydrophobicity of bastnaesite more severely.XPS shows that the combination increases the adsorption of sodium silicate on bastnaesite by forming hydrophilic Ca-SiO_(3) precipitate,which causes more serious depression on bastnaesite flotation.展开更多
Isoconversional methods combined with thermogravimetry were applied to investigate the decomposition kinetics of bastnaesite concentrates with different amounts of calcium hydroxide added.The apparent activation energ...Isoconversional methods combined with thermogravimetry were applied to investigate the decomposition kinetics of bastnaesite concentrates with different amounts of calcium hydroxide added.The apparent activation energy was calculated,and the results indicate that the overall reaction involves more than one single step.The reaction with a lower content(<15 wt%)of calcium hydroxide can be divided into two steps,while the reaction with a higher content(>15 wt%)involves another step which denotes the decomposition of newly formed calcium carbonate during roasting.The activation energy increases with increasing amount of calcium hydroxide in the lower range(0-15 wt%).This is due to the resistance of calcium hydroxide to heat and mass transport,However,more calcium can promote the decomposition reaction more effectively and thus reduce the activation energy.Nonlinear fitting was performed by fitting the experimental data to Avrami-Erofeev model to determine the reaction model and pre-exponential factor.The theoretical models were proven to be reliable for kinetic prediction.展开更多
Flotation separation and recovery of rare earth minerals(REM) have returned to an important position due to the growing strategy demand for rare earth elements(REE).In this paper,a comparative investigation into the f...Flotation separation and recovery of rare earth minerals(REM) have returned to an important position due to the growing strategy demand for rare earth elements(REE).In this paper,a comparative investigation into the floatability of bastnaesite((Ce,La)FCO3) was conducted by using three di/trialkyl phosphate collectors,di(2-ethylhexyl) phosphate(DEHPA),dibutyl phosphate(DBP) and tributyl phosphate(TBP).The density functional theory(DFT) computation recommends that the chemical activity of the three phosphate collectors is in order of DEHPA≥ DBP >> TBP,and their hydrophobization assuggested by the IgP(oil-water partition coefficient) value is in the order of DEHPA> TBP> DBP.The micro-flotation indicates that the preferable pH values for flotation of bastnaesite with the three phosphate collectors are 7.0-8.0,and DEHPA achieves much higher flotation recovery of bastnaesite,followed by DBP,and then TBP,which coincides with their reactivity and hydrophobicity,the two prerequisites for froth flotation.The contact angle,zeta potential,Fourier transform infrared spectroscopy(FTIR) and X-ray photoelectron spectroscopy(XPS) deduce that DEHPA likely reacts with the Ce(Ⅲ)atoms of bastnaesite interface through its O atom(s) of the P(=O)-O-group to generate the Ce-O-P bonds,and its two 2-ethylhexyl groups orient outside for attaching bubbles,resulting in flotation enrichment of bastnaesite.Furthermore,this investigation offers a novel strategy for developing collectors in selective beneficiation of REM.展开更多
基金supported by the the National Key R&D Program of China(No.2021YFC2900800)National Natural Science Foundation of China(Nos.52425406,51874247,51922091,and 52204285)+4 种基金the Open Research Fund of State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization(No.CNMRCUKF2001)Science and Technology Major Project of Ordos City-Iconic Innovation Team and “Rejuvenating Inner Mongolia through Science and Technology”(No.202204/2023)Yueqi Outstanding Scholar Award of CUMTB(No.202022)Funded by Open Foundation of State Key Laboratory of Mineral Processing(No.BGRIMM-KJSKL-2023-05)Fundamental Research Funds for the Central Universities(Ph.D.Top Innovative Talents Fund of CUMT BBJ2024048)。
文摘Effectively separating bastnaesite from calcium-bearing gangue minerals(particularly calcite)presents a formidable challenge,making the development of efficient collectors crucial.To achieve this,we have designed and synthesized a novel,highly efficient,water-soluble cationic collector,N-dodecylisopropanolamine(NDIA),for use in the bastnaesite-calcite flotation process.Density functional theory(DFT)calculations identified the amine nitrogen atom in NDIA as the site most susceptible to electrophilic attack and electron loss.By introducing an OH group into the traditional collector dodecylamine(DDA)structure,NDIA provided additional adsorption sites,enabling synergistic adsorption on the surface of bastnaesite,thereby significantly enhancing both the floatability and selectivity of these minerals.The recovery of bastnaesite was 76.02%,while the calcite was 1.26%.The NDIA markedly affected the zeta potential of bastnaesite,while its impact on calcite was relatively minor.Detailed Fourier-transform infrared spectroscopy(FTIR)and X-ray photoelectron spectroscopy(XPS)results elucidated that the―NH―and―OH groups in NDIA anchored onto the bastnaesite surface through robust electrostatic and hydrogen bonding interactions,thereby enhancing bastnaesite's affinity for NDIA.Furthermore,in situ atomic force microscopy(AFM)provided conclusive evidence of NDIA aggregation on the bastnaesite surface,improving contact angle and hydrophobicity,and significantly boosting the flotation recovery of bastnaesite.
基金financially supported by the National Natural Science Foundation of China(No.52174236)Fundamental Research Funds for the Central Universities(No.FRF-DF-23-001)the Natural Science Foundation of Inner Mongolia of China(Nos.2024MS05061 and 2023LHMS05050)。
文摘Rare earth elements have been widely applied in various sectors.Bastnaesite and monazite are crucial rare earth minerals,and flotation is a vital technique for recovering fine-grained rare earth minerals and separating them from associated gangue minerals such as fluorite and apatite.Flotation collectors play a key role in selectively adsorbing valuable minerals,enhancing their surface hydrophobicity,which has prompted considerable research interest.However,the interaction between minerals and reagents relies on the reactivity and selectivity of the reagent groups,as well as the reactive properties of the surface atoms of the minerals.This study proposes the use of H_(2)O_(2)oxidation to enhance the flotation process of rare earth minerals.The flotation experiments demonstrated that pre-adding H_(2)O_(2)before introducing the flotation collector significantly improved the grade and recovery of rare earth concentrates.The adsorption mechanisms of 2-hydroxy-3-naphthyl hydroxamic acid collector on rare earth mineral surfaces before and after H_(2)O_(2)pre-oxidation were studied.The 2-hydroxy-3-naphthyl hydroxamic acid interacts with Ce^(3+)on the surface of unoxidized rare earth minerals,forming chelate compounds with five-membered ring structures.The H_(2)O_(2)exhibited potent oxidizing properties and oxidized the Ce^(3+)on the bastnaesite and monazite surfaces to more stable Ce^(4+),which demonstrated stronger binding capability with hydroxamic acid.
基金Project(NDRC high-tech No.606,2009) supported by the Major Industries Technological Development Special Fund of Development and Reform Commission,ChinaProject(50934004) supported by the National Natural Science Foundation of China
文摘Sulfuric acid leaching process was applied to extracting rare earth（RE） from roasted ore of Dechang bastnaesite in Sichuan,China.The effect of particle size,stirring speed,sulfuric acid concentration and leaching temperature on RE extraction efficiency was investigated,and the leaching kinetics of RE was analyzed.Under selected leaching conditions,including particle size（0.074-0.100 mm）,sulfuric acid concentration 1.50 mol/L,mass ratio of liquid to solid 8 and stirring speed 500 r/min,the leaching kinetics analysis shows that the reaction rate of leaching process is controlled by diffusion through the product/ash layer which can be described by the shrinking-core model,and the calculated activation energy of 9.977 kJ/mol is characteristic for a diffusion-controlled process.
基金Project(50974042)supported by the National Natural Science Foundation of ChinaProject(20090042120015)supported by Scientific Research Special Foundation of Doctor Subject of Chinese UniversitiesProject(N090302007)supported by the Fundamental Research Funds for the Central Universities,China
文摘The leaching kinetics of bastnaesite concentrate in HCl solution was investigated with respect to the effects of HCl concentration by changing HCl concentration,leaching temperature,liquid to solid ratio,and particle size.A particle size of 25 μm was required to leach 89.6% RE2（CO3）3 and 1.5%REF3 at 90 ℃ for 90 min,when HCl concentration was 6 mol/L and liquid to solid ratio was 15：1.The leaching kinetics of bastnaesite concentrate is represented by shrinking core model with diffusion through a porous product layer.The activation energies for the dissolution reaction of RE2（CO3）3 and REF3 were calculated to be 59.39 kJ/mol and 66.13 kJ/mol respectively.
基金the National Key R&D Program of China(No.2021YFC2900800)National Natural Science Foundation of China(Nos.51922091,51874247 and 52204285)+1 种基金Sichuan Science and Technology Program(Nos.2023NSFSC1978 and 2022YFS0455)Open Foundation of State Key Laboratory of Mineral Processing(No.BGRIMM-KJSKL-2023-05).
文摘Rare earth element is an important strategic metal,but the supply of high purity rare earth ores is growing slowly,which is in sharp contradiction with the rapidly growing demand.Froth flotation has been confirmed to be an effective method to separate bastnaesite from its gangue minerls.However,the traditional collectors are facing serious problems in flotation separation of minerals,requiring the addition of excess depressant and regulator in the flotation process.Herein,we proposed and synthesized novel Gemini hydroxamic acids Octyl-bishydroxamic acid(OTBHA),Decyl-bishydroxamic acid(DCBHA)and Dodecyl-bishydroxamic acid(DDBHA)as the collectors in bastnaesite-barite flotation system.The effect of different carbon chain lengths on the molecular properties were explored by density functional theory(DFT)calculations.DCBHA possessed a stronger reactivity compared with OCBHA and DDBHA.The flotation results verified the consistency of the computational calculation about the performance prediction of Gemini hydroxamic acids.Compared with OCBHA and DDBHA,DCBHA displayed superior collecting affinity toward bastnaesite,and did not float barite.Zeta potential results showed that the presence of DCBHA increased the potential of bastnaesite,while it had almost no effect on barite,indicating DCBHA had a stronger affinity for bastnaesite.Then,Fourier transform infrared(FTIR)and X-ray photoelectron spectroscopy(XPS)analyses indicated that the adsorption mechanism was due to two hydroxamate groups of DCBHA co-anchored on bastnaesite surface by forming five-membered hydroxamic―(O―O)―Ce complexes.In addition,atomic force microscopy(AFM)clearly observed that DCBHA uniformly aggregated on bastnaesite surface,which increased surface contact angle and improved the hydrophobicity of bastnaesite.
文摘A bastnaesite crystal about 12×20 mm 2 in size collected from a pegmatitic aegirine augite barite bastnaesite vein of the Maoniuping rare earth deposit, Mianning County, Sichuan Province, has been analyzed for La, Ce, Pr and Nd by synchronous radiative X ray fluorescence(SRXRF) technics at the National BEPC Laboratory. The results show an apparent compositional variation along vertical and horizontal sections accross the crystal which may be divided into three compositional zones(A, B and C). Significant difference exists between the inner portion(zone A), averaging at 28 35% La 2O 3, 35 04% CeO 2, 2 01% Pr 6O 11 and 5 44% Nd 2O 3, and the outer portion(zone B), averaging at 32 81% La 2O 3, 42 26% CeO 2 3 30% Pr 6O 11 and 7 08%. Nd 2O 3, of the crystal. Only one analysis is available on the egde of the crystal(zone C) yielding 14 50% La 2O 3, 21 41% CeO 2, 4 19% Pr 6O 11 and 16 71% Nd 2O 3, which demonstrates probably fractionations between LREE and HREE. The La/Ce ratio, however, is nearly constant around 0 84±0 08 among the three zones, while the La/Pr and La/Nd ratios erratically fluctuate due to low and variable contents of Pr and Nd. These results indicate that the REE bearing hydrothermal system underwent a significant compositional change during the stepwise growth of the bastnaesite crystal.
文摘The flotation behaviour and mechanism of bastnaesite with N-hydroxyl phthalicimide were investigated by ξ-potential measurement,infrared spectrum and quantum chemistry calculation.The results show that 3 oxygen atoms from N-hydroxyl phthalicirnide chelate the rare earth ions on the surface of bastnaesite to form double five-chain O=C-N-O- RE(Ⅲ)-O chelate which is chemically adsorbed on the surface of bastnasite,thus making N-hydroxyl phthalicimide an effective collector for bastnaesite.
文摘Vapor phase extraction and mutual separation of rare earth (RE) elements from bastnaesite concentrate were investigated using stepwise chlorination chemical vapor transport reactions mediated by vapor complexes LnAl n Cl 3 n +3 (Ln=RE elements). The bastnaesite was heated to 800 K and chlorinated between 800～1300 K with C+Cl 2+SiCl 4 to remove CO 2, SiF 4 and high volatile chlorides. At the temperature of 1300 K for 6 h, the resulted RE chlorides were chemically transported and mutual separated with the vapor complexes while CaCl 2 and BaCl 2 were remained in the residues. Significantly different CVT characteristics were observed for gradually decreased and wave form temperature gradients.
文摘The content of REE(La.Ce.Pr.Nd.Sm) in bastnaesite was measured by synchrotron radiation X-ray fluorescence microprobe.Scanning analysis makes use of excitation of the REE K lines between 33 and 50 keV.SR white beam from a Wiggler source at the Beijing Electron Positron Collider(BEPC) of the National Laboratory,in order to excite the REE.The bastnaesite from the same mineral area was powdered to particle size≤300 mesh.It was then divided into two parts.One portion was used to be determined by XRF after depositing with oxalate and transforming into oxide.The other was pressed into disk without any binder as the reference sample.The weight and the diamieter of the disk were 15 g and 26 mm respectively.
基金the financial support from the National Key R&D Program of China(No.2022YFC2905800)the National Natural Science Foundation of China(Nos.52174242,52130406)。
文摘To explore the spontaneous magnetization of iron-bearing rare earth ores during suspension roasting,binary minerals containing hematite and bastnaesite were used to investigate the effects of the roasting temperature,roasting time,and bastnaesite-to-hematite mass ratio on in-situ reduction of hematite in a N_(2) atmosphere.Relevant analytical tests were used to explore the mineral phase evolution during roasting,the magnetism and microstructure of the roasted products,the phase composition,and the surface element valence of concentrate.It was found that magnetic separation of the iron concentrate afforded an iron grade of 68.87% and a recovery of 93.18% under the optimum roasting conditions.During roasting,bastnaesite decomposed to generate CO_(2) and CO,and the compact structure of hematite was gradually destroyed,resulting in microcracks.Subsequently,the CO entered the surface of the hematite through the microcracks and reacted to form a magnetite shell,and the magnetite-encapsulated hematite particles were recovered via low-intensity magnetic separation.
基金supported by National Natural Science Foundation of China (52104287,91962223)Hubei Key Laboratory for Efficient Utilisation and Agglomeration of Metallurgic Mineral ResourcesOpen Foundation of State Key Laboratory of Mineral Processing (BGRIMM-KJSKL-2022-14)。
文摘Bastnaesite((Ce,La,Pr,Nd)CO_(3)F) is a significant light rare earth mineral found in nature,known for its fine-grained properties.Flotation is commonly employed for the recovery of fine-grained bastnaesite particles.Collectors serve as an essential flotation reagent that enhance the surface hydrophobicity of target minerals.A novel collector,N-hydroxy-9-octadecenamide(N-OH-9-ODA),was synthesised in this study.N-OH-9-ODA exhibits superior selectivity compared to the traditional collector oleic acid in the flotation separation of bastnaesite and fluorite.The experimental and co mputational results indicate that N-OH-9-ODA exhibits superior selectivity due to its higher adsorption affinity for bastnaesite surface compared to fluorite surface.The zeta potential and the binding energies of the Ce 3d peaks in the X-ray photoelectron spectrum(XPS) of bastnaesite surface exhibit significant shifts.Conversely,fluorite surface demonstrates minimal alterations in its zeta potential and the binding energies of the Ca 2p peaks in its XPS after its interaction with N-OH-9-ODA.
基金Project supported by the National Key R&D Program of China (2022YFC2905800)National Natural Science Foundation of China(52174242)。
文摘To investigate the thermal decomposition behavior and reaction kinetics of bastnaesite in suspension roasting,the gas and solid products of bastnaesite roasted in N2 and air atmospheres were examined using a gas analyzer,X-ray diffraction(XRD),scanning electron microscopy(SEM),and energy dispersive spectrometry(EDS).Subsequently,the kinetic parameters of bastnaesite in the suspension roasting process were derived and calculated using the isothermal method.The results show that the decomposition product of bastnaesite in N_(2) is CeOF.However,once the roasting temperature exceeds 600℃,CO is generated in addition to CO_(2),and all the XRD diffraction peaks of CeOF are shifted to the right,indicating that CO_(2) can oxidize CeOF and lead to the transformation of Ce(Ⅲ) into Ce(Ⅳ).When roasted in air,the decomposition product CeOF can be completely converted to CeF3 and Ce_(7)O_(12) as it easily oxidizes.Additionally,the reaction rate of bastnaesite in air is higher than that of N_(2),and the starting reaction temperature is lower than that of N_(2).A large number of irregular cracks and holes appear on the surface of solid-phase products following suspension roasting,which are due to the thermal decomposition of bastnaesite that produces CO_(2) as well as the reconstruction of the lattice of the solid-phase products.The reaction kinetic model of bastnaesite roasted in N_(2)(temperature range 600-750℃) and air(temperatu re range 500-575℃) confo rms to the A_(3/2) model with the mechanism function G(α)=-ln(1-α)^(2/3),and the reaction activation energy is 59.78 kj/mol and lnA is 1.65 s^(-1) in N_(2) atmosphere.In air,the reaction activation energy is 100.30 kj/mol and lnA is 9.63 s^(-1).
基金Project supported by the National Natural Science Foundation of China(22178392)the Fundamental Research Funds for the Central Universities of Central South University,China(2022ZZTS0493)。
文摘The separation of rare earths is difficult due to their similar properties and the complex characteristics of associated vein o res.Complexation-ultrafiltration(CUF)and shear induced o rderly dissociation coupling with ultrafiltration(SIODUF)were used to separate metal ions(M,M=La(Ⅲ),Ce(Ⅳ)and Ca(Ⅱ))from simulated bastnaesite leaching solution using acidic phosphonic chitosan(aPCS)and rotating disk membrane.Effect of simultaneous removal of metallic ions was investigated by CUF,and suitable conditions were obtained for C/M 10.0(mass ratio of complexant to metal ions)and pH 5.0.The shear stabilities of aPCS-M complexes were explored at different pH values and the results show that the complexes can dissociate at a certain rotational speed,the critical one.The critical s hear rates of aPCS-La,aPCS-Ce and aPCS-Ca complexes at pH 5.0 were calculated as 1.42×10^(5).1.69×10^(5) and 9.75×10^(4) s^(-1),respectively.The order of complexes shear stability is aPCS-Ca aPCS-La<aPCS-Ce.The high selective separation of M and regeneration of aPCS were achieved by SIODUF in the light of the difference of aPCSM complexes shear stabilities.The separation coefficientsβLa/Ce andβCa/La reach 31.2 and 53.9,respectively.
基金supported by the National Natural Science Foundation of China(51404035)Beijing Nova program(Z161100004916108)
文摘To clearly elucidate the oxidative roasting behaviors of the bastnaesite, the thermal decomposition and oxidation of the bastnaesite concentrate in inert and oxidative atmosphere have been investigated in detail. Experimental data indicated that the initial decomposition temperature of the concentrate under N2 atmosphere is 150 ℃ higher than that under O2 atmosphere,most likely because the oxidation of the cerium induces the decomposition of the concentrate. For the roasted samples under N2 atmosphere at500 ℃ and above,the oxidation efficiency of the cerium is 19.8%-26.8% because of the fact that rareearth fluorocarbonate is first decomposed to form rare-earth oxyfluoride and CO2, and the cerium oxyfluoride is then partially oxidized by the CO2 gas. The rest cerium in these samples can be further oxidized in air at room temperature, with the oxidation efficiency of the cerium gradually increasing to above 80% in 7 d. This can be attributed to the obvious changes in the inner morphology of the roasted samples under N2 atmosphere at high temperatures, which largely induce the diffusion of the air and improves the oxidation activity of CeOF, and further induces the oxidation of CeOF by the air. XRD and XPS techniques were used to further verify the significant differences in the thermal decomposition behaviors of the bastnaesite concentrate under N2 and O2 atmosphere. Moreover, no oxidation of Pr^（3＋） to Pr^（4＋） in the roasted samples under both N2 and O2 atmosphere is observed. This gives an overall understanding of the oxidative roasting of the bastnaesite concentrate without additives.
基金supported by Program for Changjiang Scholars and Innovative Research Team in University of China(IRT0974)National Natural Science Foundation of China(50574069)Industrial Research Chair Program in Oil Sands Engineering from Natural Sciences and Engineering Research Council(NSERC)
文摘To understand the flotation mechanism of bastnaesite using reactive oily bubble, the interaction between bastnaesite parti-cles and reactive oily bubbles was investigated by electro-kinetic studies, induction time measurements and small-scale flotation ex-periments. The bastnaesite flotation could be seen as a hetero-coagulation between bastnaesite particles and reactive oily bubbles which was confirmed by the zeta potential distribution and induction time measurements from pH 4.8 to pH 9.0. The small-scale flotation tests were consistent with the hetero-coagulation results, and showed a better flotation of reactive oily bubble than air bubble among all pH range. The interaction force between bastnaesite particles and reactive oily bubbles was evaluated by the classical DLVO theory. It indicated that the attachment could be predicted well by the DLVO theory only in a restricted pH range due to the absence of hydrophilic interaction repulsion force and chemical interaction force.
基金Project supported by National Basic Research Program of China(973 Program)(2012CBA01205)
文摘Extracting rare earths from bastnaesite concentrate treated by calcification transition was studied through the single factor test and XRD patterns of bastnaesite after calcification and slags after leaching in HCl solution. And the effects of the main calcified parameters such as temperature, liquid/solid and calcified time on transition performance of bastnaesite were investigated. It was found that under the optimal conditions of calcification temperature of 250 oC, liquid/solid of 20 mL/g, calcification time of 180 min, the highest leaching rate of rare earth were obtained, with the leaching ratio of rare earths 83.70% and Ce 77.01%, La 90.55%, Nd 92.03%, respectively; loss rates of fluorine with different calcification conditions were always less than 1% and XRD patterns of calcification slags and leaching slags showed that fluorine existed in the form of CaF2.
基金supported by the National Natural Science Foundation of China(51574240,U1704252)Natural Science Foundation of Jiangsu Province(BK20150192).
文摘The structural and electronic properties of bastnaesite were studied by using the first-principles method based on the density functional theory(DFT).The geometry structure of bastnaesite was first optimized,and then the Mulliken populations,electron density and density of states were calculated and further analyzed in detail.The calculation results reveal that it mainly ruptures along the ionic Ce-O and Ce-F bonds during the cleavage of bastnaesite,leaving≡Ce^+,≡F^-and≡CO3^-dangling bonds exposed on the cleavage surface of bastnaesite.Combined with contact angle measurement,surface complexation theory and XPS analysis,the implications of structural and electronic properties on bastnaesite flotation reactions were studied.The hydration of exposed strong ionic bond on cleavage surface results in hydrophilic surface.According to surface complexation theory,the formed surface groups are≡CeOH^0,≡CO3 H^0 and≡FH^0 groups.The investigated metal ions and flotation reagents complex with surface≡CeOH^0 groups,while≡CO3H^0 and≡FH^0 groups are not involved in the complexation.The high activity of Ce atoms facilitates these surface reactions.
基金Project supported by the National Natural Science Foundation of China(51764045)the Open Project of State Key Laboratory of Mineral Processing(BGRIMM-KJSKL-2020-23)+2 种基金the Excellent Youth Foundation of IMUST(2017YQL05)the Inner Mongolia Natural Science Foundation(2020LH05027,2019MS05039)the Inner Mongolia Major Basic Research Open Project(0406091701)。
文摘Bastnaesite is an important rare earth mineral and is usually beneficiated by flotation.Sodium silicate is commonly used to depress calcium-bearing gangue minerals,however it can also depress bastnaesite when Ca^(2+) ions exist in the pulp.In this study,the effect of Ca^(2+) ions and sodium silicate individually or in combination on bastnaesite flotation was studied through micro-flotation,zeta potential,fluorescence spectroscopy and X-ray photoelectron spectroscopy(XPS) measurements.Micro-flotation results show that the combination of Ca^(2+) ions and sodium silicate depresses bastnaesite more severely due to their synergistic effect.Zeta potential results show that the combination renders the surface potential of bastnaesite negatively shifted more significantly.Fluorescence spectroscopy shows that the combination decreases the surface hydrophobicity of bastnaesite more severely.XPS shows that the combination increases the adsorption of sodium silicate on bastnaesite by forming hydrophilic Ca-SiO_(3) precipitate,which causes more serious depression on bastnaesite flotation.
基金Project supported by the National Basic Research Program(973 Program,2012CBA01205)。
文摘Isoconversional methods combined with thermogravimetry were applied to investigate the decomposition kinetics of bastnaesite concentrates with different amounts of calcium hydroxide added.The apparent activation energy was calculated,and the results indicate that the overall reaction involves more than one single step.The reaction with a lower content(<15 wt%)of calcium hydroxide can be divided into two steps,while the reaction with a higher content(>15 wt%)involves another step which denotes the decomposition of newly formed calcium carbonate during roasting.The activation energy increases with increasing amount of calcium hydroxide in the lower range(0-15 wt%).This is due to the resistance of calcium hydroxide to heat and mass transport,However,more calcium can promote the decomposition reaction more effectively and thus reduce the activation energy.Nonlinear fitting was performed by fitting the experimental data to Avrami-Erofeev model to determine the reaction model and pre-exponential factor.The theoretical models were proven to be reliable for kinetic prediction.
文摘Flotation separation and recovery of rare earth minerals(REM) have returned to an important position due to the growing strategy demand for rare earth elements(REE).In this paper,a comparative investigation into the floatability of bastnaesite((Ce,La)FCO3) was conducted by using three di/trialkyl phosphate collectors,di(2-ethylhexyl) phosphate(DEHPA),dibutyl phosphate(DBP) and tributyl phosphate(TBP).The density functional theory(DFT) computation recommends that the chemical activity of the three phosphate collectors is in order of DEHPA≥ DBP >> TBP,and their hydrophobization assuggested by the IgP(oil-water partition coefficient) value is in the order of DEHPA> TBP> DBP.The micro-flotation indicates that the preferable pH values for flotation of bastnaesite with the three phosphate collectors are 7.0-8.0,and DEHPA achieves much higher flotation recovery of bastnaesite,followed by DBP,and then TBP,which coincides with their reactivity and hydrophobicity,the two prerequisites for froth flotation.The contact angle,zeta potential,Fourier transform infrared spectroscopy(FTIR) and X-ray photoelectron spectroscopy(XPS) deduce that DEHPA likely reacts with the Ce(Ⅲ)atoms of bastnaesite interface through its O atom(s) of the P(=O)-O-group to generate the Ce-O-P bonds,and its two 2-ethylhexyl groups orient outside for attaching bubbles,resulting in flotation enrichment of bastnaesite.Furthermore,this investigation offers a novel strategy for developing collectors in selective beneficiation of REM.
