Conceptual Process to Produce ThO2 from Monazite


This study level process design represents an economically viable method for extracting thorium dioxide and other rare earth elements from monazite ore. This paper incorporates results from the 2019 capstone project from the honors Design Internship in Green Engineering in Chemical and Biomolecular Engineering. In this activity, senior students in Chemical Engineering at the University of Tennessee (UT) focused on the development and study of a process for the recovery of thorium dioxide and P2O5 from monazite. While not mandated, the process offers rare earth oxides as attractive byproducts. The project focused on recovery of byproducts rather than the creation or addition to waste streams. Additionally, (1) the process economics relied heavily on recovery of rare earth byproducts, (2) thorium handling portions of the process could be effectively segregated from rare earth and phosphate handling portions of the process, and (3) thorium and uranium content of waste streams should be carefully managed and eliminated where possible.

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  1. 1.

    Ault T, Van Gosen B, Krahn S, Croff A (2016) Natural thorium resouces and recovery options and impacts. Nucl Technol 194:136–151

    Article  Google Scholar 

  2. 2.

    Bennett B, Connoly-Horton, Hay K, Johnson J (2019) Extraction of thorium dioxide and other REE oxides from monazite ore, Final Report for CBE 488: Honors Design in Green Engineering, University of Tennessee

  3. 3.

    Chelgani S, Chehreh RM, Leistner T, Gutzmer J, Peuker UA (2015) A review of rare earth minerals flotation: monazite and xenotime. Int J Min Sci Technol 25(6):877–883.

    Article  Google Scholar 

  4. 4.

    Gaurav D, Malgorzata ML, Eslamimanesh A, Wang P, Anderko A, Riman RE, Navrotsky A (2019) Rare earth sulfates in aqueous systems: thermodynamic modeling of binary and multicomponent systems over wide concentration and temperature ranges. J Chem Thermodyn 131:49–79

    Article  Google Scholar 

  5. 5.

    Gordy, M., Counce, R. M., Zhang, P., Nimkar, R., and Watson, J. S. (2019) “H3PO4 production process utilizing phosphatic clay as feed material,” J Min Metall Explor, (online)

  6. 6.

    IIOT, 2019,

  7. 7.

    Kumari A, Panda R, Jha MK, Kumar JR, Lee JY (2015) Process development to recover rare earth metals from monazite mineral: a review. Miner Eng 79:102–115.

    Article  Google Scholar 

  8. 8.

    Long K R, Van Gosen B S, Foley N K and Cordier D, (2010) The principal rare earth elements deposits of the United States—a summary of domestic deposits and a global perspective, U.S.G.S. Scientific Investigations, Report 2010–5220, Reston VA

  9. 9.

    OLI Systems Inc,2018,

  10. 10.

    Rodliyah I, Rochani S, Wahyudi T (2015) Extraction of rare earth metals from monazite mineral using acid method. Indonesian Mining J 18(1):39–45

    Google Scholar 

  11. 11.

    Ulrich GD, Vasudevan PT (2004) Chemical engineering process design and economics a practical guide, vol 2, 2nd edn. Process (Ulrich) Publishing

  12. 12.

    USGS, 2019,

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OLI Systems Inc. provided assistance in development of computer-aided process modeling.


This research is funded by the Electric Power Research Institute (EPRI).

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Correspondence to Bradley Bennett.

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Bennett, B., Counce, R.M., Zhang, P. et al. Conceptual Process to Produce ThO2 from Monazite. Mining, Metallurgy & Exploration 37, 1317–1327 (2020).

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  • Chemical engineering
  • Process design
  • Simulation
  • Thorium
  • Rare earth elements