Thermal decomposition of bastnaesite in an inert atmosphere and influence on flotation behavior

Abstract

This study aimed to elucidate the influence of thermal decomposition under an inert atmosphere on the phase composition, microstructure, and flotation performance of bastnaesite. Experiments showed that decomposition was strongly temperature-dependent. After complete decomposition, the release of CO₂ increased the rare earth oxide grade from 72.90wt% to 86.83wt%, accompanied by an increase in the Ce oxidation degree. Major decomposition products included rare earth oxyfluoride (REOF), rare earth trifluoride (REF₃), and Ce₇O₁₂, with some products showing low crystallinity. The decomposition damaged the particle structure, resulting in the extensive lamellar cracking, a significant increase in specific surface area, and partial fragmentation of the particles. Flotation tests revealed that optimum recovery was achieved at pH 8.00–9.00. However, thermal decomposition increased the initial pulp pH to almost 11.00, making pH adjustment difficult. Salicylhydroxamic acid (SHA) was adsorbed on the surfaces by both physical and chemical interactions, with chemical adsorption being significantly enhanced after decomposition. During flotation, SHA was distributed not only on particle surfaces but also in internal pores after decomposition. Due to the phase and microstructural changes, the required dosage of SHA increased from 20 mg·L⁻¹ for the raw ore to 250 mg·L⁻¹. These results provide insights into the development of reagents suitable for the flotation of bastnaesite roasting products.

Keywords

bastnaesite / thermal decomposition / phase transformation / flotation behavior / adsorption mechanism

References

[1] Z.C. Shuai, Y.M. Zhu, P. Gao, and Y.X. Han, Rare earth elements resources and beneficiation: A review, Miner. Eng., 218(2024), art. No. 109011.

[2] Cheng SK, Li WB, Han YX, Sun YS, Gao P, Zhang XL. Recent process developments in beneficiation and metallurgy of rare earths: A review. J. Rare Earths, 2024, 42(4): 629

[3] Li JF, Li JM, Tian L, Wang J, Xiao YF, Ma ZY. Extraction of rare earths from ion-adsorption type rare earth ore by indigenous microbial community. Int. J. Miner. Metall. Mater., 2025, 32(8): 1848

[4] Li WB, Chen JJ, Cheng SK, Sun JY, Zhang XL. Thermal decomposition mechanism and kinetics of bastnaesite in suspension roasting process: A comparative study in N₂ and air atmospheres. J. Rare Earths, 2024, 42(9): 1809

[5] C. Liu, L.H. Xu, J.S. Deng, et al., A review of flotation reagents for bastnäsite-(Ce) rare earth ore, Adv. Colloid Interface Sci., 321(2023), art. No. 103029.

[6] Y. Wang, D.H. Wang, L.H. Xu, et al., Synthesis and utilization of a novel oleate hydroxamic acid collector for the flotation separation of bastnaesite from barite, Miner. Eng., 204(2023), art. No. 108405.

[7] Xu LH, Liu C, Deng JS, et al. . Flotation and adsorption of novel Gemini decyl-bishydroxamic acid on bastnaesite: Experiments and density functional theory calculations. Int. J. Min. Sci. Technol., 2023, 33(10): 1193

[8] Q.M. Nie, T.S. Qiu, H.S. Yan, and Y.G. Li, Flotation separation of bastnaesite from fluorite with an eco-friendly depressant polyepoxysuccinic acid and its depression mechanism, Appl. Surf. Sci., 590(2022), art. No. 152941.

[9] E. Muhoza, K. Gibson, W.C. Zhang, and S.H. Amini, Evaluation of lactic and succinic acids as green depressants for selective flotation separation of bastnaesite from calcite, Miner. Eng., 204(2023), art. No. 108435.

[10] J. Yu, S. Liu, C. Cheng, S.M. Xiong, and G.Y. Liu, The effect mechanism of calcite or quartz particles towards bastnaesite flotation with octyl hydroxamic acid, Chem. Eng. Sci., 268(2023), art. No. 118391.

[11] Owens CL, Schach E, Heinig T, Rudolph M, Nash GR. Surface nanobubbles on the rare earth fluorcarbonate mineral synchysite. J. Colloid Interface Sci., 2019, 552: 66

[12] Y.R. Chen, V.N.T. Truong, X.N. Bu, and G.Y. Xie, A review of effects and applications of ultrasound in mineral flotation, Ultrason. Sonochem., 60(2020), art. No. 104739.

[13] J.H. He, P. Gao, S. Yuan, et al., High efficiency separation of bastnaesite (REFCO₃) and monazite (REPO₄) in mixed rare earth concentrate by heating under N₂ and leaching with HCl/AlCl₃, Hydrometallurgy, 228(2024), art. No. 106338.

[14] Yang ZR, Bian X, Wu WY. Flotation performance and adsorption mechanism of styrene phosphonic acid as a collector to synthetic (Ce,La)₂O₃. J. Rare Earths, 2017, 35(6): 621

[15] Zhang LH, Li WB, Cheng SK, et al. . Enhanced flotation separation of bastnaesite and monazite by suspension roasting: A study of flotation performance and mechanisms. J. Rare Earths, 2026, 44(3): 957

[16] Zhao N, Zhang Q, Ma HW, et al. . Advancing the recovery of iron and rare earth elements from the solid waste at Bayan Obo. Int. J. Min. Sci. Technol., 2025, 35(2): 295

[17] Ning JL, Gao P, Wang Y, et al. . Mineralogical characterization and flotation properties of rare earths in refractory iron tailings subjected to hydrogen-based mineral phase transformation. Int. J. Miner. Metall. Mater., 2025, 32(6): 1309

[18] Zhao LS, Wang LS, Shuai GH, Long ZQ, Cui DL, Huang XW. Thermal decomposition and oxidation of bastnaesite concentrate in inert and oxidative atmosphere. J. Rare Earths, 2018, 36(7): 758

[19] Zhang Q, Sun YS, Han YX, Gao P, Li WB. Isothermal and non-isothermal decomposition mechanisms of bastnaesite during the hydrogen-based mineral phase transformation. Int. J. Hydrogen Energy, 2024, 68: 929

[20] Yang WL, Xu JL. Drop spreading and penetrating on micro/nano particle sintering porous with multiscale structure. Colloids Surf. A, 2017, 516: 9

[21] Ivanova AS. Structure, texture, and acid-base properties of alkaline earth oxides, rare earth oxides, and binary oxide systems. Kinet. Catal., 2005, 46(5): 620

[22] Wen SM. Thermodynamic theory of flotation for a complex multiphase solid–liquid system and high-entropy flotation. Int. J. Miner. Metall. Mater., 2024, 31(6): 1177

[23] Cullity BD, Stock SR. Elements of X-ray Diffraction, 20013rd ed.New Jersey, Prentice Hall: 161

[24] N. Buatong, C. Ruttanapun, and C. Sriwong, Synthesis of reduced graphene oxide quantum dots from graphene oxide via hydrothermal process and theirs structural, luminescence and magnetic properties, J. Taiwan Inst. Chem. Eng., 142(2023), art. No. 104667.

[25] E.A. Lalla, A. Sanz-Arranz, M. Konstantinidis, et al., Raman-IR spectroscopic structural analysis of rare-earth (RE³⁺) doped fluorotellurite glasses at different laser wavelengths, Vib. Spectrosc., 106(2020), art. No. 103020.

[26] Schilling C, Hofmann A, Hess C, Ganduglia-Pirovano MV. Raman spectra of polycrystalline CeO₂: A density functional theory study. J. Phys. Chem. C, 2017, 121(38): 20834

[27] Cao Z, Cheng ZY, Wang JL, Cao YD. Synergistic depression mechanism of Ca²⁺ ions and sodium silicate on bast-naesite flotation. J. Rare Earths, 2022, 40(6): 988

[28] Meng QY, Yuan ZT, Li LX, Lu JW, Yang JC. Modification mechanism of lead ions and its response to wolframite flotation using salicylhydroxamic acid. Powder Technol., 2020, 366: 477

[29] Khadikar PV, Pol B, Ali SM. Vibrational spectra and thermodynamic functions of salicylhydroxamic acid. Spectrochim. Acta, Part A, 1986, 42(6): 755

[30] Qin WQ, Ren LY, Xu YB, Wang PP, Ma XH. Adsorption mechanism of mixed salicylhydroxamic acid and tributyl phosphate collectors in fine cassiterite electro-flotation system. J. Cent. South Univ., 2012, 19(6): 1711

[31] Kaczor A, Szczepanski J, Vala M, Proniewicz LM. Matrix-isolation and computational study of salicylhydroxamic acid and its photochemical degradation. Phys. Chem. Chem. Phys., 2005, 7(9): 1960

[32] Zhang ZY, Jiang L, Guo WD, Yang J, Liu DF, Chi RA. Flotation behavior and adsorption mechanism of 2-hydroxy-3-naphthyl hydroxamic acid on bastnaesite surface. J. Rare Earths, 2025, 43(5): 1084

[33] Nehra P, Khatri A, Kumar A, Singh S, Rana PS. Synthesis and characterization of rare earth metal doped tungsten trioxide photocatalyst for degradation of Rhodamine B dye. J. Rare Earths, 2023, 41(9): 1302

[34] Wang GF, Mu QY, Chen T, Wang YD. Synthesis, characterization and photoluminescence of CeO₂ nanoparticles by a facile method at room temperature. J. Alloy. Compd., 2010, 493(1): 202

[35] A.A. Zaki, M. Khalafalla, K.H. Alharbi, and K.D. Khalil, Synthesis, characterization and optical properties of chitosan–La₂O₃ nanocomposite, Bull. Mater. Sci., 45(2022), No. 3, art. No. 128.

[36] Kustova GN, Obzherina KF, Batsanova LR. The infrared absorption spectra of oxyfluorides of the rare earth metals. J. Appl. Spectrosc., 1968, 9(3): 947

[37] M.N. Brekhovskikh, L.A. Vaimugin, L.V. Moiseeva, L.I. Demina, K.S. Nikonov, and V.E. Shukshin, Synthesis of anhydrous cerium tetrafluoride, J. Fluorine Chem., 275(2024), art. No. 110275.

[38] W.L. Xiong, J. Deng, K.L. Zhao, W.Q. Wang, Y.H. Wang, and D.Z. Wei, Bastnaesite, barite, and calcite flotation behaviors with salicylhydroxamic acid as the collector, Minerals, 10(2020), No. 3, art. No. 282.

[39] Brennan BJ, Chen J, Rudshteyn B, et al. . Molecular titanium–hydroxamate complexes as models for TiO₂ surface binding. Chem. Commun., 2016, 52(14): 2972

[40] Zhao C, Sun CY, Yin WZ, Luo BB. An investigation of the mechanism of using iron chelate as a collector during scheelite flotation. Miner. Eng., 2019, 131: 146

[41] R.C. Chapleski Jr, A.U. Chowdhury, A.K. Wanhala, et al., A molecular-scale approach to rare-earth beneficiation: Thinking small to avoid large losses, iScience, 23(2020), No. 9, art. No. 101435.

[42] Chapleski RCJr, Chowdhury AU, Wanhala AK, et al. . Improving rare-earth mineral separation with insights from molecular recognition: Functionalized hydroxamic acid adsorption onto bastnäsite and calcite. Langmuir, 2022, 38(18): 5439

[43] Sarvaramini A, Azizi D, Larachi F. Hydroxamic acid interactions with solvated cerium hydroxides in the flotation of monazite and bastnäsite—Experiments and DFT study. Appl. Surf. Sci, 2016, 387: 986

[44] H.R. Zhou, S. Liu, H. Yi, S.X. Song, and F.F. Jia, Flotation of bastnaesite by mixed collectors and adsorption mechanism, Chem. Phys. Lett., 830(2023), art. No. 140793.

[45] Q. Zhang, Y.S. Sun, P. Gao, and Y.X. Han, Hydrogen-based mineral phase transformation of bastnaesite: Detailed assessment of physicochemical properties and flotation behavior, Chem. Eng. J., 500(2024), art. No. 156992.

RIGHTS & PERMISSIONS

University of Science and Technology Beijing