Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Article
  • Published:

Selective sulfidation of metal compounds

Nature volume 602, pages 78–83 (2022)Cite this article

Subjects

Abstract

There is urgent, unprecedented demand for critical by-product and co-product metallic elements for the infrastructure (magnets, batteries, catalysts and electronics) needed to power society with renewable electricity1,2,3. However, the extraction of d-block and f-block metals from mineral and recycled streams is thermodynamically difficult, typically requiring complete dissolution of the materials, followed by liquid–liquid separation using metal-ion complexing or chelating behaviour4,5. The similar electronic structure of these metals results in poor separation factors, necessitating immense energy, water and chemicals consumption6,7,8. Here a metal-processing approach based on selective anion exchange is proposed. Several simple process levers (gas partial pressure, gas flowrate and carbon addition) are demonstrated to selectively sulfidize a target metal from a mixed metal-oxide feed. The physical and chemical differences between the sulfide and oxide compounds (for example, density, magnetic susceptibility and surface chemistry) can then be exploited for vastly improved separation compared with liquid–liquid methods9. The process conditions of sulfidation are provided for 56 elements and demonstrated for 15 of them. An assessment of the environmental and economic impacts suggests a path towards 60–90% reductions in greenhouse gas emissions while offering substantial capital cost savings compared with liquid–liquid hydrometallurgy.

Access through your institution
Buy or subscribe

This is a preview of subscription content, access via your institution

Access options

Access through your institution

Buy this article

  • Purchase on SpringerLink
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: The S2/SO2 ratio for selective sulfidation of metals and the corresponding gaseous space time, space velocity and CDSR levers.
Fig. 2: Application of selective sulfidation for LIB recycling, rare-earth magnet recycling and rare-earth mineral processing.
Fig. 3: Capital costs and environmental impact estimates for selective sulfidation coupled with physical separation, compared with conventional hydrometallurgical processing.

Similar content being viewed by others

Data availability

All data relevant to the results presented are included herein, within the Supplementary Information or available from the corresponding author upon request.

Code availability

Spreadsheets and code supporting technoeconomic analysis and life cycle assessment are available on the Harvard Dataverse repository at https://doi.org/10.7910/DVN/193PW2.

References

  1. Cheisson, T. & Schelter, E. J. Rare earth elements: Mendeleev’s bane, modern marvels. Science 363, 489–493 (2019).

    Article  CAS  PubMed  ADS  Google Scholar 

  2. Harper, G. et al. Recycling lithium-ion batteries from electric vehicles. Nature 575, 75–86 (2019).

    Article  CAS  PubMed  ADS  Google Scholar 

  3. Enriquez, M. A. et al. Mineral supply for sustainable development requires resource governance. Nature 543, 367–372 (2017).

    Article  PubMed  ADS  Google Scholar 

  4. Reck, B. K. & Graedel, T. E. Challenges in metal recycling. Science 337, 690–696 (2012).

    Article  CAS  PubMed  ADS  Google Scholar 

  5. Olivetti, E. A. & Cullen, J. M. Toward a sustainable materials system. Science 360, 1396–1398 (2018).

    Article  CAS  PubMed  ADS  Google Scholar 

  6. Ciez, R. E. & Whitacre, J. F. Examining different recycling processes for lithium-ion batteries. Nat. Sustain. 2, 148–156 (2019).

    Article  Google Scholar 

  7. K Lee, J. C. & Wen, Z. Pathways for greening the supply of rare earth elements in China. Nat. Sustain. 1, 598–605 (2018).

    Article  Google Scholar 

  8. Zhao, B., Zhang, J. & Schreiner, B. Separation Hydrometallurgy of Rare Earth Elements (Springer, 2016).

  9. Bailey, G. et al. Review and new life cycle assessment for rare earth production from bastnäsite, ion adsorption clays and lateritic monazite. Resour. Conserv. Recycl. 155, 104675 (2020).

    Article  Google Scholar 

  10. Norgate, T. & Jahanshahi, S. Low grade ores—smelt, leach or concentrate? Miner. Eng. 23, 65–73 (2010).

    Article  CAS  Google Scholar 

  11. Yin, X. et al. Rare earth separations by selective borate crystallization. Nat. Commun. 8, 14438 (2017).

    Article  CAS  PubMed  PubMed Central  ADS  Google Scholar 

  12. Flytzani-Stephanopoulos, M., Sakbodin, M. & Wang, Z. Regenerative adsorption and removal of H2S from hot fuel gas streams by rare earth oxides. Science 312, 1508–1510 (2006).

    Article  CAS  PubMed  ADS  Google Scholar 

  13. Valsamakis, I. & Flytzani-Stephanopoulos, M. Sulfur-tolerant lanthanide oxysulfide catalysts for the high-temperature water-gas shift reaction. Appl. Catal. B 106, 255–263 (2011).

    CAS  Google Scholar 

  14. Pease, J. D., Curry, D. C. & Young, M. F. Designing flotation circuits for high fines recovery. Miner. Eng. 19, 831–840 (2006).

    Article  CAS  Google Scholar 

  15. Pease, J. D., Young, M. F., Curry, D. & Johnson, N. W. Improving fines recovery by grinding finer. Trans. Inst. Min. Metall. Sect. C 119, 216–222 (2010).

    Google Scholar 

  16. Han, J. et al. Effects of sodium salts on the sulfidation of lead smelting slag. Miner. Eng. 108, 1–11 (2017).

    Article  CAS  Google Scholar 

  17. Zhang, W., Zhou, Y., Zhu, J. & Pan, Y. New clean process for barium sulfide preparation by barite reduction with elemental sulfur. Ind. Eng. Chem. Res. 53, 5646–5651 (2014).

    Article  CAS  Google Scholar 

  18. Zhang, W. et al. Reaction mechanism study of new scheme using elemental sulfur for conversion of barite to barium sulfide. Powder Technol. 360, 1348–1354 (2020).

    Article  CAS  Google Scholar 

  19. Kaneko, T., Yashima, Y., Ahmadi, E., Natsui, S. & Suzuki, R. O. Synthesis of Sc sulfides by CS2 sulfurization. J. Solid State Chem. 285, 121268 (2020).

    Article  CAS  Google Scholar 

  20. Ahmadi, E. & Suzuki, R. O. An innovative process for production of Ti metal powder via TiSx from TiN. Metall. Mater. Trans. B 51B, 140–148 (2020).

    Article  ADS  Google Scholar 

  21. Afanasiev, P. et al. Preparation of the mixed sulfide Nb2Mo3S10 catalyst from the mixed oxide precursor. Catal. Lett. 64, 59–63 (2000).

    Article  CAS  ADS  Google Scholar 

  22. Ahmad, S., Rhamdhani, M. A., Pownceby, M. I. & Bruckard, W. J. Thermodynamic assessment and experimental study of sulphidation of ilmenite and chromite. Trans. Inst. Min. Metall. Sect. C 123, 165–177 (2014).

    CAS  Google Scholar 

  23. Harris, C. T., Peacey, J. G. & Pickles, C. A. Selective sulphidation and flotation of nickel from a nickeliferous laterite ore. Miner. Eng. 54, 21–31 (2013).

    Article  CAS  Google Scholar 

  24. Liu, W., Zhu, L., Han, J., Jiao, F. & Qin, W. Sulfidation mechanism of ZnO roasted with pyrite. Sci. Rep. 8, 9516 (2018).

    Article  PubMed  PubMed Central  ADS  Google Scholar 

  25. Sohn, H. Y. & Fan, D.-Q. On the initial rate of fluid–solid reactions. Met. Mater. Trans. B 48B, 1827–1832 (2017).

    Article  Google Scholar 

  26. Zagorac, D., Doll, K., Zagorac, J., Jordanov, D. & Matovic, B. Barium sulfide under pressure: discovery of metastable polymorphs and investigation of electronic properties on ab initio level. Inorg. Chem. 56, 10644–10654 (2017).

    Article  CAS  PubMed  Google Scholar 

  27. Sohn, H. Y. & Kim, B.-S. A novel cyclic process using CaSO4/CaS pellets for converting sulfur dioxide to elemental sulfur without generating secondary pollutants: Part I. feasibility and kinetics of the reduction of sulfur dioxide with calcium-sulfide pellets. Metall. Mater. Trans. B 33B, 711–716 (2002).

    Article  CAS  Google Scholar 

  28. Sahu, S. K., Chmielowiec, B. & Allanore, A. Electrolytic extraction of copper, molybdenum and rhenium from molten sulfide electrolyte. Electrochim. Acta 243, 382–389 (2017).

    Article  CAS  Google Scholar 

  29. Brown, A. M. & Ashby, M. F. Correlations for diffusion constants. Acta Metall. 28, 1085–1101 (1980).

    Article  CAS  Google Scholar 

  30. Nassar, N. T., Graedel, T. E. & Harper, E. M. By-product metals are technologically essential but have problematic supply. Sci. Adv. 1, e1400180 (2015).

    Article  CAS  PubMed  PubMed Central  ADS  Google Scholar 

  31. Olivetti, E. A., Ceder, G., Gaustad, G. G. & Fu, X. Lithium-ion battery supply chain considerations: analysis of potential bottlenecks in critical metals. Joule 1, 229–243 (2017).

    Article  Google Scholar 

  32. Dunn, J. B., Gaines, L., Sullivan, J. & Wang, M. Q. Impact of recycling on cradle-to-gate energy consumption and greenhouse gas emissions of automotive lithium-ion batteries. Environ. Sci. Technol. 46, 12704–12710 (2012).

    Article  CAS  PubMed  ADS  Google Scholar 

  33. Shi, J. et al. Sulfation roasting mechanism for spent lithium-ion battery metal oxides under SO2–O2–Ar atmosphere. JOM 71, 4473–4481 (2019).

    Article  CAS  Google Scholar 

  34. Stinn, C. & Allanore, A. In Ni-Co 2021: The 5th International Symposium on Nickel and Cobalt (eds Anderson, C. et al.) 99–110 (Springer Nature, 2021).

  35. Wagner, M.-E. & Allanore, A. Chemical thermodynamic insights on rare-earth magnet sludge recycling. ISIJ Int. 60, 2339–2349 (2020).

    Article  CAS  Google Scholar 

  36. Narayanan, R. P., Kazantzis, N. K. & Emmert, M. H. Selective process steps for the recovery of scandium from Jamaican bauxite residue (red mud). ACS Sustain. Chem. Eng. 6, 1478–1488 (2018).

    Article  CAS  Google Scholar 

  37. Jowitt, Si. M., Werner, T. T., Weng, Z. & Mudd, G. M. Recycling of the rare earth elements. Curr. Opin. Green Sustain. Chem. 13, 1–7 (2018).

    Article  Google Scholar 

  38. Wang, J. & Hu, H. Selective extraction of rare earths and lithium from rare earth fluoride molten-salt electrolytic slag by sulfation. Miner. Eng. 160, 106711 (2021).

    Article  CAS  Google Scholar 

  39. Binnemans, K., Jones, P. T., Müller, T. & Yurramendi, L. Rare earths and the balance problem: how to deal with changing markets? J. Sustain. Metall. 4, 126–146 (2018).

    Article  Google Scholar 

  40. Firdaus, M., Rhamdhani, M. A., Durandet, Y., Rankin, W. J. & McGregor, K. Review of high-temperature recovery of rare earth (Nd/Dy) from magnet waste. J. Sustain. Metall. 2, 276–295 (2016).

    Article  Google Scholar 

  41. Lin, X. et al. A novel application of hematite precipitation for high effective separation of Fe from Nd–Fe–B scrap. Sci. Rep. 9, 18362 (2019).

    Article  CAS  PubMed  PubMed Central  ADS  Google Scholar 

  42. Jönsson, C. et al. The extraction of NdFeB magnets from automotive scrap rotors using hydrogen. J. Clean. Prod. 277, 124058 (2020).

    Article  Google Scholar 

  43. Rasheed, M. Z. et al. Review of the liquid metal extraction process for the recovery of Nd and Dy from permanent magnets. Metall. Mater. Trans. B 52, 1213–1227 (2021).

    Article  CAS  Google Scholar 

  44. Li, X. Z. et al. A supramolecular lanthanide separation approach based on multivalent cooperative enhancement of metal ion selectivity. Nat. Commun. 9, 547 (2018).

    Article  PubMed  PubMed Central  ADS  Google Scholar 

  45. Jordens, A., Cheng, Y. P. & Waters, K. E. A review of the beneficiation of rare earth element bearing minerals. Miner. Eng. 41, 97–114 (2013).

    Article  CAS  Google Scholar 

  46. Chi, R., Li, Z., Peng, C., Gao, H. & Xu, Z. Preparation of enriched cerium oxide from bastnasite with hydrochloric acid by two-step leaching. Metall. Mater. Trans. B 37, 155–160 (2006).

    Article  Google Scholar 

  47. Merritt, R. R. High temperature methods for processing monazite: II. Reaction with sodium carbonate. J. Less Common Met. 166, 211–219 (1990).

    Article  CAS  Google Scholar 

  48. Woods, D. R. in Rules of Thumb in Engineering Practice 376–436 (Wiley-VCH, 2007).

  49. Nuss, P. & Eckelman, M. J. Life cycle assessment of metals: a scientific synthesis. PLoS ONE 9, e101298 (2014).

    Article  PubMed  PubMed Central  ADS  Google Scholar 

  50. Skinner, B. J. Earth resources (minerals/metals/ores/geochemistry/mining). Proc. Natl Acad. Sci. USA 76, 4212–4217 (1979).

    Article  CAS  PubMed  PubMed Central  ADS  Google Scholar 

  51. Jacob, K. T. & Iyengar, G. N. K. Thermodynamic study of Fe2O3–Fe2(SO4)3 equilibrium using an oxyanionic electrolyte (Na2SO4–I). Metall. Trans. B 17, 323–329 (1986).

    Article  Google Scholar 

  52. Hsieh, K. C. & Chang, Y. A. A solid-state EMF study of ternary Ni–S–O, Fe–S–O, and quaternary Fe–Ni–S–O. Metall. Trans. B 17, 133–146 (1986).

    Article  Google Scholar 

  53. Dwivedi, R. K. & Kay, D. A. R. Thermodynamics of the oxidation of rare earth oxysulfides at high temperatures. Metall. Trans. B 15, 523–528 (1984).

    Article  Google Scholar 

  54. Akila, R., Jacob, K. T. & Shukla, A. K. Gibbs energies of formation of rare earth oxysulfides. Metall. Trans. B 18B, 163–168 (1987).

    Article  CAS  ADS  Google Scholar 

  55. Dwivedi, R. K. Determination of the Thermodynamic Properties of Rare Earth-Oxygen-Sulfur Systems at High Temperatures. PhD Thesis, McMaster Univ. (1982).

  56. Suponitskii, Y. L., Kuz’micheva, G. M. & Eliseev, A. A. Lanthanide oxide sulphides. Russ. Chem. Rev. 57, 209–220 (1988).

    Article  ADS  Google Scholar 

  57. Wang, M. Enthalpy of formation of LiNiO2, LiCoO2 and their solid solution, LiNi1−xCoxO2. Solid State Ionics 166, 167–173 (2004).

    Article  CAS  Google Scholar 

  58. Chang, K., Hallstedt, B. & Music, D. Thermodynamic and electrochemical properties of the Li–Co–O and Li–Ni–O systems. Chem. Mater. 24, 97–105 (2011).

    Article  Google Scholar 

  59. Konings, R. J. M. et al. The thermodynamic properties of the f-elements and their compounds. Part 2. The lanthanide and actinide oxides. J. Phys. Chem. Ref. Data 43, 013101 (2014).

    Article  ADS  Google Scholar 

  60. Kriklya, A. I., Bolgar, A. S. & Pribyl’skii, N. Y. Heat capacity and enthalpy of y-Dy2S3 over a wide range of temperature. Sov. Powder Metall. Met. Ceram. 31, 697–700 (1992).

    Article  Google Scholar 

  61. Chakraborti, N. Modified predominance area diagrams for the Fe–S–O system. Can. J. Chem. Eng. 61, 763–765 (1983).

    Article  CAS  Google Scholar 

  62. Madon, N. & Strickland-constable, R. F. Production of carbon disulfide. Ind. Eng. Chem. 50, 1189–1192 (1958).

    Article  CAS  Google Scholar 

  63. Fogler, H. S. Elements of Chemical Reaction Engineering (Prentice Hall, 2016).

  64. Sohn, H. Y. Review of fluid-solid reaction analysis—Part 2: single porous reactant solid. Can. J. Chem. Eng. 97, 2068–2076 (2019).

    Article  CAS  Google Scholar 

  65. Sohn, H. Y. & Szekely, J. A structural model for gas–solid reactions with a moving boundary—III. Chem. Eng. Sci. 27, 763–778 (1972).

    Article  CAS  Google Scholar 

  66. Sohn, H. Y. & Szekely, J. The effect of intragrain diffusion on the reaction between a porous solid and a gas. Chem. Eng. Sci. 29, 630–634 (1974).

    Article  CAS  Google Scholar 

  67. Ishida, M. & Wen, C. Y. Comparison of kinetic and diffusional models for solid–gas reactions. AIChE J. 14, 311–317 (1968).

    Article  CAS  Google Scholar 

  68. Sohn, H. Y. & Perez-Fontes, S. E. Application of the law of additive reaction times to fluid–solid reactions in porous pellets with changing effective diffusivity. Met. Mater. Trans. B 41B, 1261–1267 (2010).

    Article  Google Scholar 

  69. Hirschfelder, J. O., Curtiss, C. F. & Bird, R. B. Molecular Theory of Gases and Liquids (John Wiley, 1954).

  70. Berard, M. F., Wirkus, C. D. & Wilder, D. R. Diffusion of oxygen in selected monocrystalline rare earth oxides. J. Am. Ceram. Soc. 51, 643–647 (1968).

    Article  CAS  Google Scholar 

  71. Cussler, E. L. Diffusion: Mass Transfer in Fluid Systems (Cambridge Univ. Press, 2009).

  72. Deen, W. M. Introduction to Chemical Engineering Fluid Dynamics (Cambridge Univ. Press, 2016).

  73. Freer, R. Self-diffusion and impurity diffusion in oxides. J. Mater. Sci. 15, 803–824 (1980).

    Article  CAS  ADS  Google Scholar 

  74. Liao, B. Q., Wan, C. R. & Wang, J. A concept for the estimation of HETS for rare earth separations in extraction columns. Sep. Sci. Technol. 39, 2597–2607 (2004).

    Article  CAS  Google Scholar 

  75. Flett, D. S. Solvent extraction in hydrometallurgy: the role of organophosphorus extractants. J. Organomet. Chem. 690, 2426–2438 (2005).

    Article  CAS  Google Scholar 

  76. Towler, G. & Sinnott, R. Chemical Engineering Design (Elsevier, 2013).

  77. Cheng, C. Y. & Zhu, Z. Solvent extraction technology for the separation and purification of niobium and tantalum: A review. Hydrometallurgy 107, 1–12 (2011).

    Article  Google Scholar 

  78. Dincer, I. & Bicer, Y. Mitacs Accelerate Project Final Report (2015).

  79. Green, D. W. & Perry, R. H. Perry’s Chemical Engineer’s Handbook (McGraw-Hill, 2008).

  80. Christensen, P. & Dysert, L. Cost Estimate Classification System as Applied in Engineering, Procurement, and Construction for the Process Industries. AACE International Recommended Practice No. 18R-97 COST, TCM Framework: 7.3 - Cost Estimating and Budgeting (2005).

  81. Mineral Commodity Summaries 2021 (USGS, 2021).

  82. Annual Coal Report 2020 (USEIA & USDOE, 2021).

  83. Henry Hub Natural Gas Spot Price (USEIA, 2021).

  84. Misaka, T. & Mochizuki, Y. In Electrosatic Precipitation (ed. Yan, K.) 518–522 (Springer, 2009).

  85. Bleiwas, D. I. Estimated Water Requirements for the Conventional Flotation of Copper Ores USGS Open-File Report 2012-1089 (2012).

  86. Bleiwas, D. I. Estimates of Electricity Requirements for the Recovery of Mineral Commodities, with Examples Applied to Sub-Saharan Africa USGS Open-File Report 2011-1253 (2011).

  87. Bezuidenhout, G. A., Davis, J., van Beek, B. & Eksteen, J. J. Operation of a concentrated mode dual-alkali scrubber plant at the Lonmin smelter. J. South. African Inst. Min. Metall. 112, 657–665 (2012).

    CAS  Google Scholar 

  88. King, M. J., Davenport, W. G. & Moats, M. S. Sulfuric Acid Manufacture—Analysis, Control and Optimization (2013).

  89. ISO 14044 (ISO, 2006).

  90. Ecoinvent-Association ecoinvent 3.6 (Ecoinvent Center, 2019); www.ecoinvent.org

  91. Klett, C., Reeb, B., Missalla, M. & Schmidt, H.-W. in Light Metals 2011 (ed. Lindsay, S. J.) 125–130 (John Wiley, 2011).

  92. Fu, C. & Gundersen, T. Using exergy analysis to reduce power consumption in air separation units for oxy-combustion processes. Energy 44, 60–68 (2012).

    Article  CAS  Google Scholar 

  93. de Bakker, J. Energy use of fine grinding in mineral processing. Metall. Mater. Trans. E 1, 8–19 (2014).

    ADS  Google Scholar 

  94. TRACI 2.1: Tool for Reduction and Assessment of Chemicals and Other Environmental Impacts (USEPA, 2014); https://www.epa.gov/chemical-research/tool-reduction-and-assessment-chemicals-and-other-environmental-impacts-traci

  95. Carbon Dioxide Emissions Coefficients (USEIA, 2021).

  96. Stinn, C. & Allanore, A. Selective sulfidation of metal compounds—supporting computing files. Harvard Dataverse https://doi.org/10.7910/DVN/193PW2 (2021).

Download references

Acknowledgements

We thank the US Department of Energy and the US National Science Foundation for their financial support; H. Higuchi and Sumitomo Metal Mining for providing samples of scandium oxide; and K. Daehn, A. Culbertson, T. Close, L. Rush, A. Caldwell and M. E. Wagner for their insight.

Author information

Authors and Affiliations

  1. Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA

    Caspar Stinn & Antoine Allanore

Authors
  1. Caspar Stinn
    View author publications

    You can also search for this author inPubMed Google Scholar

  2. Antoine Allanore
    View author publications

    You can also search for this author inPubMed Google Scholar

Contributions

C.S. and A.A. designed the project, wrote the manuscript and prepared the figures. C.S. carried out the experiments, modelling and analysis.

Corresponding author

Correspondence to Antoine Allanore.

Ethics declarations

Competing interests

The authors have filed for intellectual property protection pertaining to work herein.

Peer review

Peer review information

Nature thanks Junwei Han, Fanran Meng, Fiseha Tesfaye and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data figures and tables

Extended Data Fig. 1 Gas species partial pressures as thermodynamic levers to control compound stability.

a, Sc-O-S Kellogg diagram (T = 1,000 °C, 1 atm), illustrating the role of \({P}_{{{\rm{S}}}_{2}}\), \({P}_{{{\rm{O}}}_{2}}\) and \({P}_{{{\rm{SO}}}_{2}}\) on scandium compound stability. b, Fe–O–S–C predominance diagram, illustrating the role of PCO, \({P}_{{{\rm{CO}}}_{2}}\), \({P}_{{{\rm{S}}}_{2}}\) and \({P}_{{{\rm{SO}}}_{2}}\) on iron compound stability (\({P}_{{{\rm{S}}}_{2}}\) fixed at 0.05 atm). The sulfide becomes the only stable compound of Fe in the presence of carbon at increasing \({P}_{{{\rm{S}}}_{2}}\) values, as for many critical metals including Co, In, Mn, Ni, Sn, W and Zn. In a, b, solid lines correspond to phase domains, dotted lines correspond to equilibrium gas compositions at 1 atm total pressure and dashed lines correspond to \({P}_{{{\rm{SO}}}_{2}}\).

Extended Data Fig. 2 Reaction and solution contributions to sulfidation selectivity.

a, b, (See Supplementary equations (1), (2), (3), (4), (5), (6) and (7) in Supplementary Information). When \({\psi }_{rxn}\gg {\psi }_{sol}\), the sulfidation thermodynamics are reaction-dominated, solution effects are minimal and the sulfidation thermodynamics are well described by those of the pure compound. When \({\psi }_{sol}\gg {\psi }_{rxn}\), the sulfidation thermodynamics are solution-dominated and reaction effects are minimal, the sulfidation thermodynamics are not well described by those of the pure compound, and knowledge of the solution behaviour is essential to determine sulfidation spontaneity. c, d, Equilibrium S2/SO2 ratio as a function of sulfur partial pressure and temperature at 1 atm for a gas consisting exclusively of sulfur–oxygen-containing species at equilibrium. As derived in the Supplementary Information, the equilibrium \({P}_{{{\rm{S}}}_{2}}\) / \({P}_{{{\rm{SO}}}_{2}}\) ratio that satisfies \(\psi \) corresponds to (\({P}_{{{\rm{S}}}_{2}}\)/\({P}_{{{\rm{SO}}}_{2}}\))crit.

Extended Data Fig. 3 Experimental devices used for sulfidation and recovery.

a, A packed-bed, flow-through reactor (12), is placed in a furnace (1) equipped with an alumina tube (2) to conduct selective sulfidation using elemental sulfur evaporated from the bottom of the tube (11). b, A Hallimond cell is used for the recovery by flotation of the sulfide phases formed in a.

Extended Data Fig. 4 Lanthanum oxide sulfidation reaction kinetics as measured in a graphite packed bed reactor.

a, Conversion versus time as a function of temperature shows reaction rate increasing with temperature, consistent with the notion of thermal activation of the reaction. b, Sulfur partial pressure corresponding to conversion rate in a. c, Modified Sherwood number \((Sh{\prime} )\) for lanthanum oxide sulfidation kinetics experiments. Following Sohn’s criteria65, for \(Sh{\prime} > 30\) external mass transfer limitations to the observed reaction rate are negligible. d, Fluid–solid reaction modulus \((\hat{\sigma })\) for lanthanum oxide sulfidation kinetic experiments. For \({\hat{\sigma }}^{2} < 0.01\), intergrain diffusion limitations to the observed rate of reaction are negligible65. Intragrain diffusion limitations are addressed in the Supplementary Information and Supplementary Table 3. e, Comparison of the kinetically limited (Supplementary Information) rate of oxygen liberation for sulfidation versus sulfur gas concentration. The slope of natural log of the oxygen liberation rate vs the natural log of the sulfur concentration is the reaction order, observed to be approximately first order with respect to sulfur. f, Arrhenius plot of the natural log of the reaction rate constant vs inverse temperature. The activation energy is found to be 114 kJ mol−1, with a pre-exponential factor of 1.08 × 104 s−1.

Extended Data Fig. 5 Selective sulfidation of LiNi1/3Mn1/3Co1/3O2 (abbr. NMC111 or NMC333) separated into Ni-rich sulfide (1), Co-rich sulfide (2) and Mn oxysulfide (3) phases.

a, Optical dark field image showing Ni, Co and Mn-rich phases coalesced to approximately 100–500 μm in size that support physical separation following sulfidation at 1,000 °C. b, SEM–EDS analysis reveals distinct Ni-rich sulfide (1, Ni0.75Co0.25S), Co-rich sulfide (2, Ni0.33Co0.67S) and Mn oxysulfide (3, MnO0.2S0.8) phases. c, SEM–EDS maps illustrate minimal Mn inclusion in Ni–Co phases and vice versa post-sulfidation.

Extended Data Fig. 6 Selective sulfidation of calcined rare-earth, iron, boron ((Nd,Pr,Dy)–Fe–B) magnet separated into an iron-rich sulfide phase (1) with neodymium-rich oxide (2) inclusions.

a, Upon sulfidation, calcined (Nd,Pr,Dy)–Fe–B particles 90–212 μm in size sintered to approximately 1–2 mm in size, with Nd-rich oxide (1) regions approximately 20–100 μm in size that are large enough to support physical separation from the bulk Fe-rich sulfide (2) phases (SEM/BEC image). b, SEM–EDS analysis reveals minimal inclusion of Fe,Dy into the Nd,Pr-rich inclusions and vice versa post-sulfidation.

Extended Data Fig. 7 Sulfidative sintering and selective sulfidation of synthetic defluorinated, dethoriated, light rare-earth element bastnaesite (Ln2O3) separates into neodymium-rich and lanthanum-rich phases.

a, Ln2O3 particles (25–45 μm) sulfidized with carbon in an alumina flow-through packed-bed reactor at 1,400 °C sintered to approximately 100–300 μm in size (darkfield optical image). b, Ln10OS14 (1) and Ln2O2S (2) approximately 20–100 μm in size are observed to form upon sulfidation, large enough to support physical separation (polarized optical image, 90°). c, EPMA/WDS elemental analysis reveals sulfidation is selective, with Nd enriched in the oxygen-rich Ln2O2S phase (2) and La enriched in the sulfur-rich Ln10OS14 phase (1).

Extended Data Fig. 8 Flowsheet of a generic selective sulfidation process.

The process consists of selective sulfidation in a multihearth fluidized bed reactor, product comminution and physical separation via froth flotation, and downstream gas handling and treatment via a cyclone separator for solid particle removal and acid plant for SO2 recovery, and assumes an equimolar, mixed, binary oxide feed. The system boundary for life cycle assessment is depicted, over the impact categories of global warming potential (GWP), terrestrial acidification (TA) and water resource depletion (WRD), for a functional unit of 1 kg of selective sulfidation feed. The impacts of flows originating within the system boundary are evaluated from the cradle to usage in the process, while the impacts of flows originating outside the system boundary are evaluated from the system gate to usage in the process. The impacts of flows exiting within the system boundary are evaluated from outlet of the process to the grave, while flows exiting outside the system boundary are evaluated from production in the process to the system gate.

Extended Data Fig. 9 Capital cost (CAPEX) and operating cost (OPEX) distributions for the generic selective sulfidation process (Extended Data Fig. 8, Supplementary Figs. 1–3).

Distributions for selective sulfidation with and without feed pretreatments and with and without CDSR are determined via Monte Carlo simulation, with probability distributions for CAPEX, OPEX and operating condition parameters described in Supplementary Tables 14, 15. Pretreatment steps for feed drying, sintering and roasting/calcination each marginally increase the CAPEX and OPEX of selective sulfidation by 10% to 20%. CDSR generally decreases CAPEX at the expense of increases in OPEX and environmental impacts (Extended Data Fig. 10).

Extended Data Fig. 10 Global warming potential (GWP), water resource depletion (WRD) and terrestrial acidification (TA) distributions for the generic selective sulfidation process (Extended Data Fig. 8, Supplementary Figs. 1–3), with and without feed pretreatments, with and without CDSR, for a functional unit of 1 kg of selective sulfidation feed.

Distributions are determined via Monte Carlo simulation, with probability distribution for operating condition parameters described in Supplementary Tables 14, 15. The inclusion of feed pretreatments increases GWP by about 50%, WRD by 30% and TA by double, while CDSR increases GWP by a factor of 3–5 times and WRD by a factor of 3–4 times. The bimodal nature of the GWP distribution is due to differences in oxygen content of the three model chemistries considered in the Monte Carlo simulation, highlighting the role of system chemistry in determining environmental impact.

Supplementary information

Supplementary Information

This file contains Supplementary Methods.

Supplementary Tables

This file contains Supplementary Tables 1–33; see Summary tab for table descriptions.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Stinn, C., Allanore, A. Selective sulfidation of metal compounds. Nature 602, 78–83 (2022). https://doi.org/10.1038/s41586-021-04321-5

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s41586-021-04321-5

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing