(450a) A Comprehensive Techno-Economic-Environmental Assessment of Conventional Processes Used in Extracting Rare Earth Elements Concentrates from Bastnaesite Ores.

As the U.S. embarks on plans to bring back rare earth elements (REEs) operations, there is
renewed interest in designing processes that are both economical and environmentally friendly.
This interest is backed by the fact that the U.S. once dominated the REE industry (1960s-1980s
[1]), but the processes employed then were costly and polluted the environment. Thus, they
cannot resume. The long-term aim of this work is to propose innovative processes that improve
past and current practices for the extraction of REEs from different sources and their purification
into commercial-grade RE compounds. A first step towards achieving this goal is to understand
where the weaknesses from previous operations lie so that we can propose better solutions.

In this work, we focus on the simulation and techno-economic and environmental assessment of
the processes conventionally used in extracting REEs in the U.S. and China. Based on [2], most
of these processes involve dissolution/precipitation steps. We extend the nonlinear
programming model developed in [3] to compute the equilibrium composition at each of the
processing steps and perform sensitivity analyses to understand the recovery trends of species
in the aqueous and solid phases along the process flow sheets. The economic assessment is
conducted using Aspen Capital Cost Estimator [4], while the environmental assessment is
performed using the EPA’s GREENSCOPE tool [5].

As an example of the results, we considered the processing of Bastnaesite ore concentrates
(2.8 tons total rare earth oxide(TREO)) containing light REEs (Ce, La, Sm, Pr, Nd, Eu, Gd),
heavy REEs (Y, Ho, Yb) and impurities (Ca, Ba, Fe, Si, Th), yielding 5.6 tons of mixed rare earth
chloride concentrate to be fed into a solvent extraction circuit. The baseline case study is a
process flowsheet belonging to Molycorp Inc. U.S. described in [2] whose steps include acid
leaching, caustic conversion, evaporation and multiple washing and filtration steps. From the
economic assessment of this plant, the total capital investment comprising the installed
equipment costs, working capital and startup costs is in the order of 11 MUSD, while the
operating expenses consisting of the raw material costs, utilities and waste disposal are in the
order of 8 MUSD per year.

References:
1. Grasso, V. Rare Earth Elements in National Defense: Background, Oversight Issues,
and Options for Congress; 2013. https://sgp.fas.org/crs/natsec/R41744.pdf.
2. Dezhi, Q. Hydrometallurgy of Rare Earths; Elsevier BV, 2018.
https://www.sciencedirect.com/book/9780128139202/hydrometallurgy-of-rar….
3. Chris Laliwala, Oluwamayowa O. Amusat, and Ana I. Torres. An Optimization-Based
Law of Mass Action Precipitation/Dissolution Model. (Prepared for ESCAPE 2025).
4. Aspen Technology Inc. Aspen Capital Cost Estimator | CAPEX Estimation | AspenTech.
www.aspentech.com.
https://www.aspentech.com/en/products/engineering/aspen-capital-cost-es….
5. US EPA. GREENSCOPE: A Method for Modeling Chemical Process Sustainability |
Science Inventory |
https://cfpub.epa.gov/si/si_public_record_report.cfm?Lab=NRMRL&dirEntry….