Critical Minerals and Materials Program Accomplishments

Accomplishments in the Critical Minerals and Materials Program have been achieved through research in field work proposal (FWP) projects at NETL’s Research and Innovation Center (RIC), as well as extramural research, development, and demonstration projects conducted through funding opportunity announcements; requests for proposal awards with industrial stakeholders and numerous universities; and projects awarded under Small Business Innovation Research programs.

NETL’s Research and Innovation Center Accomplishments

NETL-RIC’s FWP portfolio has achieved notable accomplishments in the areas of domestic resource assessment and geospatial modeling; REE extraction and recovery and process development; and addressing key areas to deployment.

Domestic Resource Assessment and Geospatial Modeling

Since 2015, NETL-RIC has conducted extensive field prospecting campaigns to locate potential candidate rare earth element (REE)-containing coal-based materials. Efforts to identify promising resources are based on:

Understanding how REEs are present within the various materials (e.g., chemical phase composition and concentration), and to what extent REEs can be separated and recovered (e.g., extractability).
Developing a systematic method to predict where these resources may exist.

Classic X-ray diffraction, scanning electron microscopy and microprobe analyses, and cutting-edge analytic characterization techniques (e.g., X-ray absorption near-edge structure [XANES] analysis at the SLAC National Accelerator Laboratory) have been utilized to underpin the basis for development of novel extraction techniques (Figure 1).

Identifying the phase and oxidation state of these elements provides insight on what is being selectively targeted during extraction and what portion of the host rock can be discarded during processing.

Figure 1 — Sub-Micron REE Phase Association and Oxidation State Determination Using XANES Analysis

Understanding where promising resources may exist is being addressed by the development of a method and tool by NETL-RIC to systematically identify high-concentration and extractable CMM deposits in sedimentary systems. Because it is not currently possible to predict these locations, the basis for NETL initiating development of the Rare Earth Element Sedimentary Resource Assessment Method (REE-SED) and tool in 2018 was to support systematic prediction and assessment of domestic REE deposits from coal-based resources and other sedimentary systems [1,2].

The (REE-SED) method is the first-of-its-kind, big-data, machine learning-enabled, geoscience approach to improve prediction and identification of domestic sedimentary and coal-based resource and deposit locations containing high concentrations of CMM (Figure 2). This effort, in collaboration with industry, universities, and the U.S. Geological Survey, as well as state surveys, is key to NETL’s geo-data science modeling effort, which relies on data generation from strategic analysis of samples at the local scale. Looking ahead, REE-SED has unlimited potential and is expected to dramatically reduce the time required to locate potentially promising CMM deposits.

Figure 2 — REE-SED Assessment Methodology

REE Extraction and Recovery — Process Development

NETL-RIC has successfully produced less than 95% purity (less than 950,000 ppm) mixed rare earth oxides (MREO) from a variety of sources, including waste products such as coal ash, acid mine drainage (AMD), and other materials resulting from legacy mining operations.

Since 2015, REE extraction and recovery research at NETL-RIC has included not only physical and chemical separation efforts, but also development of advanced sorbent materials for sorption (i.e., capture) of REEs in naturally occurring coal waste streams or REEs from extraction and separation process fluids.

These transformational efforts ranged from lower technology readiness level basic laboratory-scale research to field testing of advanced sorbents at the Pittsburgh Botanical Garden, a former abandoned mine site in Pennsylvania (Figure 3). A 2020 Technology Commercialization Fund small pilot-scale project was initiated in collaboration with the University of Wyoming School of Energy Resources and other industrial partners to advance NETL-RIC’s extraction and separation process for recovery of REEs from calcium-enriched Powder River Basin ashes.

Figure 3 — NETL-RIC REE Extraction and Separation Process and Sorbent Development

Addressing Key Areas to Deployment

In addition to the development and maturation of production processes, NETL-RIC’s technology development has systematically addressed other technology areas to promote the creation of a domestic CMM industry. This effort includes the development of computational fluid dynamics (CFD) models and real-time laser-induced breakdown spectroscopy, metal organic framework-ultraviolet light source, and fiber-optic sensors to enable process control in systems that typically operate at steady-state. CFD modeling and sensor development can enable process optimization and accelerate process intensification (reducing costs), as well as assist to de-risk deployment of potential CMM facilities (Figure 4).

Figure 4 — NETL-RIC CFD Modeling and Field/Process Sensor Development

Techno-economic analysis (TEA) of separation processes has also been utilized to reduce research and development time. By identifying key areas for process optimization early in the research and development process, researchers can identify and focus on the metrics that impact cost and performance. TEA has been extensively utilized to support validation of CMM separation and extraction processes developed in NETL extramural stakeholder projects. NETL-RIC researchers have also developed a current and projected future CMM intermediate and end-product supply chain database.

Extramural CMM Research

Technology development in NETL’s federally funded extramural projects systematically focuses on field prospecting and resource assessment; integration of conventional physical beneficiation and chemical separation or hydrometallurgical processing of feedstock materials to produce high-purity coal-based MREOs; development of advanced, new-novel, transformational separation processes; TEA of conventional and transformational separation processes; and optimization and efficiency improvement of conventional separation processes to achieve system economic viability.Technology development in NETL’s federally funded extramural projects systematically focuses on field prospecting and resource assessment; integration of conventional physical beneficiation and chemical separation or hydrometallurgical processing of feedstock materials to produce high-purity coal-based MREOs; development of advanced, new-novel, transformational separation processes; TEA of conventional and transformational separation processes; and optimization and efficiency improvement of conventional separation processes to achieve system economic viability.

Since 2016, numerous extramural stakeholder extraction separation and recovery processing approaches have been identified and used to demonstrate the technical feasibility of extracting REEs from coal refuse, power generation ash, and AMD (Figure 5). By 2020, these efforts resulted in the design, construction, and operation of three first-of-a-kind, small pilot-scale facilities producing small quantities (e.g., approximately 100 g/day) of greater than 98–99% (greater than 980,000–990,000 ppm) high-purity MREOs from 300 ppm REE-containing coal-based feedstock materials using conventional physical beneficiation and hydrometallurgy (chemical separation) processes.

Figure 5 — Mixed Rare Earth Oxides Produced from Coal Refuse, Power Generation Ash, and AMD

University of Kentucky Modular Pilot-Scale CMM Separation Facility

In 2018, the University of Kentucky (UK) produced small quantities of 80–90 wt% (800,000–900,000 ppm) pure MREOs in its modular pilot-scale facility (Figure 6) from coal refuse materials from the Central Appalachian and Illinois Coal basins. Of the critical elements in UK’s REE concentrate, 45% were neodymium and yttrium, which are used in national defense technologies and the high-tech and renewable energy industries. In 2020, 98% pure MREO concentrates were produced with co-production of CMMs. Since 2021, UK has produced singular rare earth oxides (REO) at over 80% purity and has co-produced cobalt, nickel, and manganese.

Figure 6 — UK’s Modular Pilot-Scale CMM Separation Facility

West Virginia University Pilot-Scale CMM Separation Facility

Commissioned in July 2018, West Virginia University’s (WVU) bench/small pilot-scale rare earth extraction facility (Figure 7) began producing REE pre-concentrates from AMD and sludge materials from the Appalachian Coal Basin. By 2019, WVU produced approximately 80 wt% (800,000 ppm) pure MREO concentrate; in 2020, WVU succeeded in producing approximately 98 wt% (980,000 ppm) pure MREO concentrates from AMD with co-production of critical minerals. Since 2021, WVU’s pilot facility has demonstrated a production rate of 82 grams of MREO per hour with promising separation results, and has co-produced nickel, cobalt, manganese, and zinc.

Figure 7a — WVU’s Rare Earth Extraction Facility — Figure 7 — WVU’s Rare Earth Extraction Facility

Figure 7b — WVU’s Rare Earth Extraction Facility — Figure 7 — WVU’s Rare Earth Extraction Facility

Physical Sciences Inc. and Winner Water Services Pilot-Scale CMM Separation Facility

In July 2018, Physical Sciences Inc. (PSI) produced greater than 15 wt% (150,000 ppm) MREOs in their micro-pilot facility (Figure 8) in Andover, Massachusetts, using post-combustion ash that was generated in a power plant boiler that was burning East Kentucky Fire Clay coal. The micro-pilot facility was used by PSI to develop the design and operating parameters that were used to scale their process to the pilot-scale operating system with Winner Water Services (WWS) in Sharon, Pennsylvania. The PSI-WWS pilot-scale facility became operational in November 2019. Prior to the end of operations in 2022, the facility produced rare earth plus yttrium oxide at purities of over 90%, successfully separating scandium and aluminum to produce high purity scandium salt and aluminum oxide.

Figure 8 — PSI-WWS's Pilot-Scale CMM Extraction Facility. Upper Left Photo: UK’s Center of Applied Energy Research Physical Beneficiation Facility; Lower Left Photo: PSI’s Micro-Pilot Facility in Andover, Massachusetts; Right Photo: WWS’s Chemical Extraction facility in Sharon, Pennsylvania

University of North Dakota Bench-Scale CMM Separation Facility

In 2019, the University of North Dakota (UND) demonstrated in its bench-scale facility (Figure 9), the capability of producing a 65 wt% (650,000-ppm) MREO concentrate from lignite using a one-step selective mineral acid leaching process. Efforts are continuing at UND to bring its pilot-scale facility online in 2021. Since coming online in 2021, UND’s pilot-scale facility has planned for production of ~5–7 kg of greater than 70% pure REE concentrate and ~40–60 kg of 10% pure scandium-rich concentrate. The facility co-produces germanium with plans to co-produce gallium.

Figure 9 — UND’s Bench-Scale CMM Extraction Facility

Technology Advancements

Numerous additional technical contributions have resulted from conduct of these extramural stakeholder projects:

Researchers at WVU demonstrated that nearly 100% of the REEs in AMD can be recovered, and that when REEs are extracted from small AMD material drying cells (e.g., ~0.5-acre x ~10-ft deep [Figure 10]), an estimated revenue of $250,000 (or greater) can result.
Researchers at UND demonstrated the relative ease of extracting REEs that are primarily contained in the organic fraction of lignite using a one-step selective mineral acid leaching process.
Researchers at UK, in collaboration with the University of Utah, incorporated in situ sulfuric acid production through microbially enhanced heap leaching of pyrite in feedstock materials, improving coal refuse processing economics.
Each of these small-pilot-scale MREO facilities are currently implementing process design configurations for co-production of select CMMs, such as cobalt, manganese, nickel, gallium, and gadolinium.
In collaboration with Battelle Memorial Institute, Rare Earth Salts produced the first individually separated, high-purity (greater than 95%) REO from coal-based materials in 2020.

Figure 10 — AMD Stream and Small AMD Sludge Drying Cell

Research, Development, and Demonstration Assessment

Technology achievements resulting from both intramural and extramural projects have successfully demonstrated the potential for the utilization of carbon ore and coal-based resources to produce critical elements needed for the United States to drive forward the development of refineries that are essential for domestic commodity and defense product production.

The uniqueness of NETL’s program is its capability to not only impact both domestic and global technology integration across numerous supply chains and markets, but also to facilitate cross-functional technology development in and between NETL’s Crosscutting Research, Advanced Turbines, Solid Oxide Fuel Cells, and Carbon Ore Processing Technology programs, as well as NETL’s Resource Sustainability Program.

References

1. Bauer, J., Justman, D., Mark-Moser, M., Romeo, L., Creason, C. G., and Rose, K. Exploring Beneath the Basemap. In D. Wright and C. Harder (Eds) GIS for Science (vol 2). Digital released https://www.gisforscience.com/chapter5/
2. NETL, REE-SED, NETL’s REE Sedimentary Resource Assessment Method, August 2020, https://www.netl.doe.gov/sites/default/files/2020-08/REE-SED%20Infographic-01.png