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Retrospective on Recent DOE-Funded Studies Concerning the Extraction of Rare Earth Elements & Lithium from Geothermal Brines (Final Report)
Rare earth elements (REE) and lithium are non-toxic metals that are considered critical materials due to their use in electronics, magnets, batteries, and a wide variety of industrial processes important for the economy and military preparedness. Demand for REE and lithium is increasing and these critical materials are imported, so identifying and exploiting domestic sources of REE and lithium is a national priority. The U.S. Department of Energy (DOE) Geothermal Technologies Office (GTO) has been in the forefront of sponsoring research investigating the potential recovery of REE, lithium, and other critical minerals from geothermal brines. It has been proposed that the future of geothermal energy should include “hybrid systems” that combine electricity generation with other revenue-generating activities, such as recovery of valuable and critical minerals, including REE and lithium. Two recent GTO funding opportunities have focused on the recovery of REE and other valuable minerals from geothermal brines. The research supported by the GTO’s mineral recovery program is focused on three areas: resource characterization, technology for the extraction of REE, and technology for the extraction of lithium (Tables 1 and 2). This report is a retrospective study examining the outcome of GTO’s two recent mineral recovery programs (DE-FOA-0001016 in FY 2014 and DE-FOA-0001376 in FY 2016). In this report, the knowledge, technology, and techniques that were developed by researchers funded by GTO are summarized and discussed. Four projects were funded to assess the concentrations and amounts of REE found in geothermal brines and oil field produced waters. The GTO-funded studies compiled publically available data on REE concentrations from brines and produced water from all over the USA. In addition, new samples were collected and characterized from major geothermal and hydrocarbon basins in the Western USA. The studies examined the relationship between lithology and REE concentrations and developed models examining the influence of geology on REE concentrations in produced brines. It was determined that REE are frequently found at higher concentrations in oil field produced water than geothermal brines, but that some geothermal areas had significant REE resources. Significant reservoirs of REE were identified in the Western USA. In some cases, concentrations of REE were more than 1000 times the concentrations found in seawater. Collectively, these studies represent a comprehensive picture of REE resources associated with geothermal and hydrocarbon systems in the USA. The studies did not examine lithium resources, but in some cases, lithium concentration data was collected. Data from these studies are housed in the Geothermal Data Repository (GDR) and represent a significant information resource and it is recommended that these data be further analyzed in a future study. Eight projects were funded to develop new technology for REE extraction from geothermal fluids. These projects investigated sorption as an approach for removal and recovery of REE from geothermal brines. The projects investigated cutting-edge technology for selective sorption of ions from complex solutions, including the application of metal-organic frameworks and biosorbent proteins. The REE sorption studies tested different combinations of metal-binding ligands and solid supports. The most promising metal-binding ligands for REE included phosphonic acid, thiol, and carboxylic acid functional groups. Ligands were attached or incorporated into a wide variety of solid supports. In most cases, attachment was via covalent bonding to organic resins, polymers, or silica-based supports. Most of the REE projects were conducted at a low technology readiness level (TRL) and showed promise, but direct comparison between technologies was not possible based on the available information. It is recommended that testing and reporting be standardized to the extent possible to facilitate comparisons between technologies. Two projects were directed at novel lithium extraction technology. Both projects investigated the use of inorganic sorbents, including manganese oxides. One study also examined the use of metal- ion imprinted polymers as selective ion-exchange resins for the separation of lithium and manganese from brines. Both approaches showed promise for the selective extraction of lithium from brines, including potentially geothermal brines. Results from these GTO studies indicated that selective REE and lithium extraction is possible, but interference from co-occurring solutes, such as calcium, magnesium, or heavy metals, will interfere with process efficiency and negatively impact process economics. Techno-economic analysis conducted as part of the resource and technology studies suggest extraction of REE from geothermal brines is unlikely to be economically viable, especially since non-geothermal produced waters frequently have higher REE concentrations. It is recommended that benchmarks for techno-economic analysis be established to the extent possible for future studies, to facilitate direct comparison of various technologies. Based on the collective results of this program, it appears that hybrid geothermal power would benefit more from recovery of lithium and other metals, rather than REE. It is recommended that future studies be conducted at a higher- TRL and that sorbents be tested against actual geothermal fluid samples. Prior higher-TRL efforts to extract metals from geothermal brines should be further evaluated for lessons learned.
Production of Carbon Nanomaterials and Sorbents from Domestic U.S. Coal (Final Report)
The main goal of this project was to produce high-value carbon nanomaterials and carbon sorbents from domestic coal resources in a cost-effective manner. Four types of domestic coal samples were processed through a combination of deashing, devolatilization, oxidation, reduction, and activation treatments to produce graphene oxide (GO), reduced graphene oxide (RGO), and activated carbon (AC). The precursors and developed materials were extensively characterized by various methods to investigate the impact of the coal feedstock type on the yield and quality of each product. A commercial graphite-based GO sample was included in the experimental work as the baseline material for comparison with the coal-based materials developed in this work. The performed work also included a technoeconomic analysis and cost estimation for a plant processing 20 tons/day coal, a market evaluation for the graphene materials, and a technology gap analysis. A simple process by concentrated nitric acid oxidation is used to oxidize coal precursors for the production of GO. Fine oxidized coal particles that were separated from larger oxidized coal particles had significantly higher oxygen contents and were identified as coal-based GO samples. Coarse oxidized coal particles were used as precursors for production of AC. Based on the Raman spectroscopy results, coal-based GO samples exhibited G and D bands similar to those of graphite-based GO samples. X-ray photoelectron spectroscopy revealed that coal-based GO samples had surface oxygen contents of ~26-35% that were higher than the oxygen contents of graphite-based GO samples. Larger particles of oxidized coal samples were activated under different conditions to produce high surface area functionalized AC. Prepared materials had surface areas exceeding 1,500 m 2 /g and pore volumes more than 1 cm 3 /g with different pore size distributions. Reduced graphene oxide samples were prepared by thermal reduction of both coal-based and graphite-based GO samples at 170-2800 ºC. Coal-based and graphite-based RGO samples exhibited similar carbon contents, Raman spectra, and XRD profiles. Heat treatment above 1500 ºC shifted RGO to synthetic graphite. Among anthracite, bituminous, subbituminous, and lignite coals tested, anthracite was the best precursor to produce carbon nanomaterials exhibiting properties similar to those of graphite-based materials. Anthracite-based carbon nanomaterials also had the highest production yields. Technoeconomic analysis estimated the production cost of GO and RGO for anthracite-based samples at about 2,600 and 4,200 $/ton, respectively, which is about two orders of magnitude lower than the current estimated price of graphite-based materials. Several gaps to further develop the proposed technology were identified and discussed that include process and equipment optimization, process integration, need for additional bench- and pilot-scale experiments, and other items to reduce the scale up risk. Market analysis reports suggested a compound annual growth rate of 40% for graphene and related materials. Short-term applications include composites, inks, and coatings. However, energy storage applications appear to be the dominant potential long-term applications. Different applications of coal-based GO and RGO need to be explored and clear metrics and standards for each application need to be developed.
Detecting Reactive Products in Carbon Capture Polymers with Chemical Shift Anisotropy and Machine Learning
Aminopolymers are attractive sorbents for CO 2 direct air capture applications due to their high density of amine groups, which can readily react with atmospheric levels of CO 2 to form chemisorbed species. The identity of these chemisorbed species and the functional groups that form upon oxidative degradation depends on both material properties and processing conditions, forming a variety of carbonyl-type sites such as ammonium carbamates, bicarbonates, carbonates, carbamic acids, ureas, and amides. 13 C solid-state nuclear magnetic resonance (NMR) is often used to help elucidate the identity of these reacted species, but it is challenging due to the narrow chemical shift range of carbonyl sites. Herein, we demonstrate the application of a two-dimensional (2D) chemical shift anisotropy (CSA) recoupling pulse sequence (ROCSA) to obtain CSA tensor values at each isotropic chemical shift, overcoming limitations of isotropic peak resolution. CSA tensor values describe the local chemical environment and can readily differentiate between the chemisorbed and degradation products. To aid identification, we also developed a k-nearest neighbor (kNN) classification model to distinguish the functional groups via their CSA tensor parameters. This methodology was demonstrated on poly(ethylenimine) in γ-Al 2 O 3 exposed to CO 2 and showed that the chemisorbed products are ammonium carbamate and a mixed carbamate–carbamic acid species. The sample was analyzed again after desorption at 100 °C inducing mild degradation, and the remaining products were strongly bound carbamate and urea species. In conclusion, the combination of 2D CSA measurements coupled with a kNN classification model enhances the ability to accurately identify chemisorbed or degradation products in complex carbon capture materials.
Evaluation of Engineered Form MOFs CaSDB and HKUST-1
Idaho National Laboratory (INL) and Pacific Northwest National Laboratory (PNNL) have studied different sorbents for the purpose of separating krypton (Kr) and xenon (Xe). PNNL has researched various metal-organic frameworks (MOFs) that have characteristics theoretically suitable for the separation. Based on computational analysis, PNNL chose Calcium–4,4’–sulfonyl dibenzoate (CaSDB) and Hong Kong University of Science and Technology MOF1 (HKUST–1). The raw MOFs are supplied in a powder form and must be incorporated into a robust engineered form to be viable for gas separation. In 2016, PNNL produced an engineered form of CaSDB by compressing and grinding the raw MOF material. This form was sent to INL for adsorption testing. Gentle mechanical agitation of the compressed form produced a large amount of powder, resulting in the conclusion that the form was not viable for the application. In 2019, INL successfully produced two engineered forms, CaSDB–EF1 and HKUST–EF2, by incorporating the active MOF powders into a polyacrylonitrile (PAN) binder. PNNL also produced two engineered forms, CaSDB–10pmma and HKUST–10pmma, by using polymethyl methacrylate (PMMA) as a binder. Surface area analysis indicated that the forms could be viable for separations in which the CaSDB–EF1 retained 84% of the raw CaSDB surface area and CaSDB–10pmma retained 48%. HKUST–EF2 retained all the raw HKUST–1 surface area, whereas HKUST–10pmma retained only 28%. Mechanical stability testing demonstrated that the PMMA forms formed a fine powder whereas, the PAN forms did not. In general, adsorption testing showed that CaSDB–10pmma had a lower Xe breakthrough capacity than CaSDB–EF1, but a higher saturation capacity at both room temperature and at 253 K. The CaSDB MOF was intended to be used as a room temperature sorbent to capture Xe. However, both CaSDB engineered forms displayed relatively short initial break through times. Reduced temperature increased the Xe capacity of both engineered forms. HKUST–1 was expected to be effective only at sub-zero temperatures. At 195 K, HKUST–10pmma had an initial Xe breakthrough capacity of 119 mmol/ kg, compared to HKUST–EF2 at 339 mmol/ kg. The saturation capacities were 275 and 383 mmol/ kg, respectively. HKUST–10ppm also had a lower Kr capacity of 1.7 mmol/kg, whereas the HKUST–EF had a Kr capacity of 3 mmol/ kg. Test results indicate that the PAN engineered forms are a more suitable choice for the complete separation of Xe and Kr, due to the increase in initial breakthrough capacity. CaSDB allows rapid breakthrough of Kr and Xe regardless of the type of engineered form. At 253 K, it is more viable, but is still not the most effective sorbent. HKUST–EF2 demonstrated viability for Xe capture at 195 K, which may merit further study, however it may be cost prohibitive.
Modification of CO2/H2O Selectivity of Polymer Through Graphene Coating for Carbon Capture Materials
A harmful issue that needs attention and solution is the rising carbon dioxide (CO2) in our atmosphere. Carbon dioxide in our atmosphere is at an all time high and has continuously increased since the industrial revolution. It has increased tremendously going from 315 parts per million (ppm) in the 1960s up to 419.3 ppm in 2023 as shown in Figure 1. Moreover, CO2 emissions have increased from 11 billion tons/year in the 1960s to 38.6 billion tons/year in 2023. The increase in CO2 found in our atmosphere has a number of detrimental effects such as increase in global temperatures and an increase in the ocean’s acidity. Human activities are greatly involved in the cause of CO2 emissions. At Lawrence Livermore National Lab (LLNL) the Microencapsulated CO2 sorbents (MECS) division has been doing research and investigating formulations for their microcapsules. MECS are core-shell microcapsules consisted of a highly permeable polymer shell and a fluid (sodium carbonate solution) that reacts and absorbs carbon dioxide. An example of the microcapsules are shown in Figure 2. Equation 1 shows the chemical reaction of the fluid (sodium carbonate) contained in the polymer shell that acts as the carbon dioxide sorbent and becomes sodium bicarbonate. The LLNL MECS team is in the process of scaling up their microcapsules for potential applications in “carbon capture from flue gas streams generated by fossil fuel combustion in industrial plants and operations, carbon capture in breweries and soft drink manufacture, carbon capture directly from indoor air to improve its quality”. The microcapsule’s possibility for commercial applications was discovered in 2017.
Solid Sorbent Cost Sensitivity Analysis: A Framework for UNF Reprocessing Sorbent Cost Comparison
Solid sorbents have been the subject of research and development across the U.S. Department of Energy national laboratory complex for many years. They are generally accepted as a safer alternative to cryogenic distillation for noble gas capture, and they present an easier pathway in development of long-term waste forms after iodine capture. As more types of sorbents have been proposed for capture of volatile radionuclides, it has become necessary to compare them based on performance and cost criteria. This report details cost and performance information for three promising sorbents and provides a cost sensitivity analysis. The goal of this analysis is to establish a framework which can be utilized to directly compare future sorbents, with differing properties, to the sorbents discussed in this report. Direct comparison is instrumental to making informed decisions to efficiently guide research and minimize laborious detours. In all cases, sorbent capacity is a major cost driver as it influences the mass of sorbent, operational footprint, and disposal cost requirements., However, sorbent price can greatly increase the cost of a capture technology. For sorbents used in krypton capture, the purity of krypton released to storage is the highest cost driver.
Characterizing and modeling the mechanical behavior of an anion exchange membrane for carbon capture applications
A new direct air capture (DAC) technology uses a moisture swing (MS) process with anion exchange membranes, potentially offering a more energy-efficient way to remove CO₂ from the air. In this MS process, the membrane absorbs CO₂ as it dries and releases it when water is added. Understanding the mechanical behavior of these membranes is essential for improving the design and efficiency of DAC systems and prolonging sorbent lifetime. This study tested one anion exchange membrane, Fumasep’s FAA-3, under mechanical loading and various temperature and humidity conditions to measure its swelling, stiffness, strength, plastic deformation, and stress relaxation. Experimental results were used to identify a mechanical model for FAA-3 that can be used to predict the material’s nonlinear viscous behavior under various loads and environments. Unlike prior studies that assumed linear elastic behavior, this work incorporates humidity-dependent swelling, thermal expansion, and nonlinear viscoelasticity of FAA-3 in both the experiments and the model.
Strategies for design and synthesis of porous liquids toward carbon capture and separation
Porous liquids (PLs) represent a promising category of sorbents in carbon capture and separation capable of integrating the advantages of flowing liquid and porous solid systems. Well-defined pores were engineered into liquid sorbents via liquifying molecules with stiff interior voids, dissolving rigid porous hosts in flowing liquids, or dispersing porous frameworks in high steric hindrance solvents, producing type I, II, or III PLs, respectively. Unique features of PLs have triggered broad interest in exploring their applications in carbon capture and separation, in which diverse design strategies, synthesis approaches, and enhanced performance have been reported. Here, in this minireview, recent progress in the design, synthesis, and structural engineering of PLs and efforts towards the optimization of their carbon capture and separation behavior will be summarized, including the comparison between PLs with varied types. Porosity engineering into liquid sorbents provides opportunities to resolve challenging issues in conventional sorption and separation systems.
Ultra-Low SWaP CO 2 Sensing for Demand Control Ventilation (Final Report)
In this project PARC and Energy ETC aimed to develop an ultra-low cost, size, weight, and power (SWaP) printed CO 2 sensor system for occupancy detection to enable Demand Control Ventilation (DCV) on a per-room basis. The CO 2 sensor technology is based on the temperature variation when CO 2 reversibly physisorbs to a highly conductive and high surface area sorbent surface, and is compatible with integration with PARC innovations in printed sensors and flexible electronics, for which PARC is a globally leading research center. The printed CO 2 sensor itself is designed to be compatible with PARC’s “peel-and-stick” platform of ultra-low power, low-cost, distributed sensors, and to facilitate real-time DCV based on overall indoor air quality (IAQ). Previously, PARC has developed flexible hybrid electronics (FHE) compatible materials to measure humidity, temperature, light, strain, and gases such as carbon monoxide, methane, ammonia, and hydrogen sulfide. Through this project, PARC developed FHE-compatible materials to measure CO 2 . Thus, with one <$15 FHE “peel-and-stick” based sensor node, a building management system (BMS) will be able to capture a complete picture of the indoor environment. This includes IAQ, light, temperature, and other comfort factors that impact building operations. Combined with optimized DCV, this low-cost sensor capability can be a key enabler of annual primary energy savings of ~ 0.3-0.4 Quad in commercial buildings while ensuring healthy IAQ. Energy ETC is a leader in supplier-agnostic BMS deployments and will design the commissioning and deployment procedures to maximize system interoperability.
Influence of Seawater Salts on Magnesium Oxide Hydration: Implications for Carbonation
The effects of individual component salts on MgO hydration and subsequent carbonation have not been systematically investigated despite the increase in utilization of seawater and other brines in the production of MgO-containing next-generation cements, fire retardants, and sorbents for CO2. Here, we present a study of MgO hydration in the presence of individual saltwater cations at a range of concentrations, as well as binary mixtures at seawater concentrations, and subsequent carbonation. We observed that the presence of the cations increased MgO dissolution rates and that the subsequent carbonation extent of the hydrated material remained constant or even increased. Since the presence of these salts during hydration does not show negative effects on subsequent carbonation in our experimental study, the application of seawater and other brines containing high concentrations of these salts to hydrate MgO in industrial processes is likely feasible.
Quantum chemically calculated Abraham parameters for quantifying and predicting polymer hydrophobicity
The leakage and accumulation of plastic in the environment is a significant and growing problem with numerous detrimental impacts and has led to a push toward the design and development of more environmentally benign materials. To this end, we have developed a quantum chemistry-based model for predicting the mobility of polymer materials from molecular structure. Hydrophobicity is used as a surrogate for mobility given that hydrophobic interactions drive much of the partitioning of contaminants in and out of various environmentally relevant compartments. To model polymer hydrophobicity, we adjusted a previously developed Quantum Chemically Calculated Abraham Parameter model to calculate Abraham parameters of small molecules from molecular structure information. The resulting model predicted the octanol-water partition coefficient (K OW ) of polymer repeating units with a root mean square error (RMSE) of 0.48 (log scale). Additionally, the hydrophobicity of high molecular weight polymer materials was captured through solubility parameters and Nile red staining experiments from the literature and predicted with RMSEs of 1.21 (J/cc) 0.5 and 3.42 nm, respectively. Finally, to test the environmental applicability of the model, the relative adsorption capacity of three polymers was predicted and used to unify sorption isotherms across multiple sorbates and polymer sorbents.
Understanding the performance of membrane for direct air capture of CO 2
Abstract Direct air capture (DAC) of CO 2 is becoming increasingly important for reducing greenhouse gas concentrations in the atmosphere. However, the cost and energy requirements associated with DAC make it less economically feasible than carbon capture from flue gases. While various methods like solid sorbents and gas–liquid absorption have been explored for DAC, membrane processes have only recently been investigated. The objective of this study is to examine the separation performance of a membrane unit for capturing CO 2 from ambient air. The performance of a membrane depends on several factors, including the composition of the feed gas, pressure ratio, material selectivity, and membrane area. The single‐stage separation process with the co‐current flow and constant permeability flux model is evaluated using a commercial module integrated with a process simulator to separate a binary mixture of carbon dioxide and nitrogen to assess the sensitivity of selectivity on purity and recovery of CO 2 in permeate, and power requirement. Additionally, three levels of CO 2 reduction from the feed stream to the retentate stream (25%, 50%, and 75%) are studied. A trade‐off between purity and recovery factor is observed, and achieving high purity in permeate requires high concentration in the retentate.
Sorbent-coated carbon fibers for direct air capture using electrically driven temperature swing adsorption
Not Available
Multi-column evaluations for the capture and separation of krypton and xenon using mordenite based sorbents
This presentation is a high-level overview of the research at INL for the capture and separation of krypton and xenon from used nuclear fuel reprocessing off-gas.
Isotherm modeling and techno-economic analysis of a TSA moving bed process using a tetraamine-appended MOF for NGCC applications
Tetraamine-appended metal-organic frameworks (MOF) are a new family of amine-functionalized MOF materials that show potential for CO 2 capture from flue gas conditions relevant to natural gas combined cycle (NGCC) power plants. This work presents isotherm modeling of the tetraamine-appended MOF Mg 2 (dobpdc)(3-4-3)(dobpdc 4- =4,4'-dioxidobiphenyl-3,3'dicarboxylate;3-4-3=N,N'bis(3-aminopropyl)-1,4-diaminobutane), process modeling, scale up, and a techno-economic optimization of a moving bed Temperature Swing Adsorption (TSA) process for carbon capture using this sorbent. This MOF exhibits a unique two-step CO 2 adsorption profile in three different pressure ranges. Thus, arctangent-based logistic functions and, quadratic and Langmuir models were employed to represent such isotherm behavior. The results of the isotherm model show good fitting vs the experimental data with an RMSE of 0.41. Here, to model the carbon capture process, the isotherm model was embedded into a moving bed contactor model, and this was used to simulate a TSA CO 2 capture cycle and evaluate cost-optimal designs considering flue gas from a -650 MWe NGCC power plant. The capital cost model consists of CAPEX correlations for reactors, compressors, ducting, etc., while the operating costs include steam, water, chemicals, and electricity (following NETL's quality guidelines for energy systems studies). A techno-economic optimization of the capture system was performed by using NETL's Framework for the Optimization and Quantification of Uncertainty and Surrogates tool (FOQUS). Results suggest that a moving bed carbon capture system with tetraamine-appended MOF can be competitive compared to conventional MEA solvent-based capture processes for NGCC plants, when a heat recovery efficiency of at least 40% is achieved, and MOF materials can be produced at a cost below -$9/kg.
Improving the direct air capture capacity of grafted amines via thermal treatment
Elevated thermal treatments increase the CO 2 capacity of aminosilane-grafted SBA-15 sorbents through freeing up additional surface hydroxyls and favoring CO 2 binding as carbamic acid.
Iodine Capture Studies of Silver Mordenite and Novel Alternative Metal Sorbents
Radioiodine is one of the radionuclides of concern when considering reprocessing of used nuclear fuel (UNF). It is expected to be released primarily in the dissolver off-gas (DOG) stream. Sorbents that target I 2 removal from a UNF processing off gas must perform efficiently under elevated temperatures in the presence of water vapor and nitrogen oxide gasses (NOx). Many studies have been conducted that examine the adsorption of iodine species in the presence of NOx gases through reduced silver-exchanged mordenite (Ag 0 Z), a zeolite mineral. This study characterizes the effects of iodine, water vapor, and nitrogen dioxide on the adsorption of I 2 by Ag 0 Z at lower temperatures suitable for comparison with novel Cu- and Bi- bearing sorbents which offer a non-RCRA alternative. When exposed to ‘harsh’ conditions such as I 2 , H 2 O, and NO 2 vapors carried by air, Cu 2 S-polyacrylonitrile (PAN) is more efficient than Ag 0 Z and all other novel sorbents, providing with 11% I capture efficiency. However, under ‘ideal’ conditions in which I 2 is carried by dry air), Ag 0 Z is more efficient than Cu 2 S-PAN and other novel sorbents, providing 74% I capture efficiency. To investigate this result and the overall performance of all sorbents tested, several characterization techniques were employed, including thermal gravimetric analysis, scanning electron microscopy – electron dispersion X-Ray spectroscopy, powder X-ray diffraction, and X-ray photoelectron spectroscopy. These techniques are discussed within this report. This document also includes a design and test plan update from Idaho National Laboratory as the next step in testing the high performing sorbents from thin-bed tests carried out by Oak Ridge National Laboratory.