Sustainable and Energy-Efficient Production of Rare-Earth Metals via Chloride-Based Molten Salt Electrolysis

Holcombe, Benjamin; Sinclair, Nicholas; Wasalathanthri, Ruwani; Mainali, Badri; Guarr, Evan; Baker, Alexander A.; Usman, Sunday Oluwadamilola; Kim, Eunjeong; Sen-Britain, Shohini; Jin, Hongyue; McCall, Scott K.; Akolkar, Rohan

doi:10.1021/acssuschemeng.3c07720

Sustainable and Energy-Efficient Production of Rare-Earth Metals via Chloride-Based Molten Salt Electrolysis

Journal Article · Mon Feb 26 23:00:00 EST 2024 · ACS Sustainable Chemistry & Engineering

DOI:https://doi.org/10.1021/acssuschemeng.3c07720· OSTI ID:2337582

Holcombe, Benjamin ^[1]; ^[1]; Wasalathanthri, Ruwani ^[1]; Mainali, Badri ^[1]; Guarr, Evan ^[2]; ^[3]; ^[4]; Kim, Eunjeong ^[3]; Sen-Britain, Shohini ^[3]; Jin, Hongyue ^[4]; McCall, Scott K. ^[4]; ^[2]

Case Western Reserve University, Cleveland, OH (United States); Critical Materials Institute, Ames, IA (United States)
Case Western Reserve University, Cleveland, OH (United States)
Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Critical Materials Institute, Ames, IA (United States)
University of Arizona, Tucson, AZ (United States); Critical Materials Institute, Ames, IA (United States)

Neodymium metal is a critical component of rare earth magnets, essential for electric vehicles and the green energy transition, but its production has severe environmental impacts across its mining, separation, purification, and metal electrowinning steps. Specifically, conventional neodymium electrowinning in oxyfluoride molten salts using a consumable graphite anode generates greenhouse gases, e.g., carbon dioxide and perfluorocarbon (PFC). We propose an alternative chloride-based molten salt electrolysis process utilizing a novel dimensionally stable anode (DSA). Our process lowers the specific electrical energy consumption compared to the state of the art, while producing reusable chlorine gas and eliminating direct CO₂ and PFC emissions. Chloride-based molten salt electrolysis of NdCl₃ (1.65 M) added to a LiCl–KCl eutectic (45:55 wt %), while using a RuO₂-coated DSA enables high Coulombic efficiency (>80%), low specific energy consumption (2.3 kWh/kg-Nd), and excellent electrowon Nd product purity (>97 wt %). Life cycle analysis, excluding the common input feedstock (Nd₂O₃), shows that the global warming potential for the proposed chloride-based electrolysis approach is 5 kg CO₂ equivalent, compared to 9–16 kg CO₂ equivalent for the conventional process, representing a 44–69% reduction in CO₂ emissions.

View Accepted Manuscript (DOE)

Research Organization:: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)

Sponsoring Organization:: USDOE National Nuclear Security Administration (NNSA); USDOE Office of Energy Efficiency and Renewable Energy (EERE)

Grant/Contract Number:: AC52-07NA27344; EE0009434; AC02-07CH11358

OSTI ID:: 2337582

Alternate ID(s):: OSTI ID: 2376662

Report Number(s):: LLNL--JRNL-857005; 1084468

Journal Information:: ACS Sustainable Chemistry & Engineering, Journal Name: ACS Sustainable Chemistry & Engineering Journal Issue: 10 Vol. 12; ISSN 2168-0485

Publisher:: American Chemical Society (ACS)Copyright Statement

Country of Publication:: United States

Language:: English

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