Demonstration of long-term stability of solid adsorbents for direct air capture of carbon dioxide under real-world working conditions
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36 MATERIALS SCIENCE↗
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Trends in Solid Adsorbent Materials Development for CO 2 Capture
A review summarizing trends in materials development for CO 2 adsorption focusing on recent studies is given. Trends in computational investigations along with experimental findings are covered to find promising candidates in light of practical challenges imposed by process economics. Topics covered here include: introduction (climate change, CO 2 emissions mitigation, overview of classical computational CO 2 adsorption studies); CO 2 capture materials (C based materials [activated C {AC}, ordered porous C, C fiber, graphene], SiO 2 /Al 2 O 3 /zeolite [SiO 2 , Al 2 O 3 and nanoclays, zeolite], porous cryst. solids [metal-org. frameworks (MOF) {metal type and open metal sites, functionalized MOF, mol. sieves, MOF computational modeling, MOF databases}, zeolite imidazolate frameworks, covalent org. frameworks and polymers], metal oxides); and conclusions and future perspectives.
36 MATERIALS SCIENCE↗
Solid‐Adsorbed Polymer‐Electrolyte Interphases for Stabilizing Metal Anodes in Aqueous Zn and Non‐Aqueous Li Batteries
Abstract Polymers are known to adsorb spontaneously from liquid solutions in contact with high‐energy substrates to form configurationally complex, but robust phases that often exhibit higher durability than might be expected from the individual physical bonds formed with the substrate. Rational control of the physical, chemical, and transport properties of such interphases has emerged as a fundamental opportunity for scientific and technological advances in energy storage technology but requires in‐depth understanding of the conformation states and electrochemical effect of the adsorbed polymers. Here, we analyze the interfacial adsorption of oligomeric polyethylene glycol (PEG) chains of moderate sizes dissolved in protic and aprotic liquid electrolytes and find that there is an optimum polymer molecular weight of approximately 400 Da at which the highest columbic efficiency is achieved for both Zn and Li deposition. These findings point to a simple, versatile approach for extending the lifetime of batteries.
Jin, Shuo↗
Solid–Adsorbed Polymer–Electrolyte Interphases for Stabilizing Metal Anodes in Aqueous Zn and Non–Aqueous Li Batteries
Polymers are known to adsorb spontaneously from liquid solutions in contact with high-energy substrates to form configurationally complex, but robust phases that often exhibit higher durability than might be expected from the individual physical bonds formed with the substrate. Rational control of the physical, chemical, and transport properties of such interphases has emerged as a fundamental opportunity for scientific and technological advances in energy storage technology but requires in-depth understanding of the conformation states and electrochemical effect of the adsorbed polymers. Here, we analyze the interfacial adsorption of oligomeric polyethylene glycol (PEG) chains of moderate sizes dissolved in protic and aprotic liquid electrolytes and find that there is an optimum polymer molecular weight of approximately 400 Da at which the highest columbic efficiency is achieved for both Zn and Li deposition. Furthermore, these findings point to a simple, versatile approach for extending the lifetime of batteries.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Role of Amine Structure on Hydrogen Sulfide Capture from Dilute Gas Streams Using Solid Adsorbents
The hydrogen sulfide composition in biogas ranges from 0 to 5% depending on the feed source to the biogas digester. To meet renewable natural gas specifications of 0–4 ppm of H 2 S content, technologies that remove H 2 S from raw biogas feeds are needed. This contribution assesses three adsorbents with similar textural and physical properties but with different amines grafted to the surface. Specifically, materials containing primary, secondary, and tertiary amines at the end of a propyl surface linker grafted on a silica support are explored. H 2 S adsorption isotherms and cyclic studies are presented for these materials, and it is shown that secondary amines have the best amine efficiency while tertiary amines are the most stable for H 2 S capture, of the materials studied. The results suggest the consideration of secondary and tertiary amines for the design of amine adsorbents suitable for H 2 S removal in dilute gas streams over multiple cycles.
09 BIOMASS FUELS↗
Effective Strategy toward Obtaining Reliable Breakthrough Curves of Solid Adsorbents
Not provided.
Materials Science↗
Evaluation of Long-Term Storage Stability and Operational Efficiency of Rapid Cycle Amine Adsorbents
With the recent incorporation of Mars Extravehicular Activity (EVA) into the 2025 NASA roadmap, Rapid Cycle Amine (RCA) technology advancement within the Exploration Extravehicular Mobility Unit (xEMU) applies to both the upcoming Lunar Artemis missions and future human exploration of Mars. The incorporation of commercial spacesuit vendors to service NASA’s crewed-space programs since 2021 has increased the demand for regenerable, RCA-based carbon dioxide (CO2) and humidity control adsorbents. The regenerable RCA subunit is the most advanced, long-term solution for CO2 removal and humidity control, enabling both lunar and Martian EVAs. The adsorbent selected for use within the RCA unit must exhibit sufficient storage stability and operational efficiency for prolonged missions. As XploSafe worked to simultaneously develop both a recirculating sub-atmospheric test rig and adsorbents for the RCA system within the xEMU, several novel adsorbents were evaluated for long-term storage stability in support of future extended-duration missions. The chosen materials were periodically evaluated by nuclear magnetic resonance (NMR) spectroscopy, thermal desorption-coupled with gas chromatography/mass spectrometry (TD-GC/MS), and CO2 adsorption to assess long-term storage efficacy across various environmental storage conditions. NMR spectroscopy was utilized by extracting the active CO2 adsorbing chemical from the solid support with deuterated solvent and comparing the spectra over time for degradation and change. The solid adsorbents were also analyzed via TD-GC/MS to reveal any potential off-gassing chemicals over time. Additionally, XploSafe’s breakthrough test rig was utilized to dose the solid adsorbents with a 585 BTU/h metabolic rate flow-equivalent CO2 stream and monitored for 0–99% CO2 breakthrough. The performance metrics from the breakthrough analysis were compared over the storage study duration for CO2 removal and humidity control. Xplo-SA9T was evaluated for 24 months, whereas two additional adsorbent variants, MMPA-Sorbent and LPEI-Sorbent, were each evaluated for 12 months.
John R Tidwell↗
Analysis of trace halocarbon contaminants in ultra high purity helium
This study describes the analysis of ultra high purity helium. Purification studies were conducted and containment removal was effected by the utilization of solid adsorbent purge-trap systems at cryogenic temperatures. Volatile organic compounds in ultra high purity helium were adsorbed on a solid adsorbent-cryogenic trap, and thermally desorbed trace halocarbon and other contaminants were analyzed by combined gas chromatography-mass spectrometry.
Fewell, Larry L.↗
Process-informed adsorbent design guidelines for direct air capture
Direct air capture using solid adsorbents is a proven technology critical to reducing our net greenhouse gas emissions to zero and beyond. Currently, academic research into the technology mainly focuses on the development of new adsorbents. However, there is a discord between the adsorbent design and process performance. Many materials scientists focus on maximising metrics such as the CO 2 capacity of their adsorbent. Here, we combine detailed process modelling, machine learning, and extensive global sensitivity analysis, which entails varying all of the model parameters together, on a direct air capture process to show that the dry CO 2 adsorption capacity does not influence process performance for an amine-functionalised adsorbent operating in a temperature vacuum swing adsorption (TVSA) process, while it is important in a steam-assisted TVSA (S-TVSA) process. In fact, adsorption kinetics, density, and thermal conductivity are all critical attributes to obtaining a low energy penalty and reduced costs. The analysis also highlights the importance of heat transfer, directing process engineers to (alternative) adsorber designs that maximise this. By an in-depth evaluation of how process performance indicators are affected by materials properties and process operating parameters, this work provides guidance to both material scientists and process engineers towards the design of a “unicorn adsorbent” and intensified DAC processes. This will improve the performance of solid adsorbent direct air capture and help drive down the costs of this vital technology to avert the worst impacts of climate change.
42 ENGINEERING↗
Mercury Speciation and Quantification of Hanford 241-AP-107 Tank Waste Feed and Treated Samples
This report describes the second phase of a multi year project to adapt and develop an analytical technique for the low-level determination of total mercury (HgT), elemental mercury (Hg0), and monomethyl mercury (MeHg, hereafter referred to as methyl mercury) in Hanford tank waste. The focus of Phase II was to quantify the mercury (Hg) species total, elemental, and methyl mercury from a raw sample and treated (i.e., filtered and cesium-decontaminated) waste samples originating from Hanford waste tank 241-AP 107. The focus of Phase I work was to determine if mercury species can be preconcentrated from aqueous Hanford tank waste solution onto a solid adsorbent while simultaneously eliminating or very significantly reducing the parent radionuclide activity. This was demonstrated by developing protocols for the preparation, separation, and collection of total mercury and methyl mercury onto solid adsorbents, then measuring the adsorbents for radiological content at Pacific Northwest National Laboratory’s (PNNL’s) Radiochemical Processing Laboratory (RPL) on the Hanford Site. During Phase II, the Hanford tank waste material was preserved, separated (through distillation or digestion), then collected as either solid adsorbents or into liquid distillate form at the RPL and transferred to the PNNL Marine Sciences Laboratory (MSL) in Sequim, Washington, for analysis and quantification. Quantification of total, elemental, and methyl mercury was conducted under radiological control at the MSL using the ultra trace analytical capabilities available there.
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
O 2 Binding Materials and highly Efficient Modular System for Oxygen Production
The overall objective of this project was to develop innovative oxygen separation materials and technologies based on using oxygen carriers in solid form to reversibly bind oxygen for efficient separation of air to produce greater than 95% purity of oxygen (O 2 ). These materials were then be made into solid adsorbents and membranes for O 2 production processes. The goal of this technology development project was to achieve a bed-factor of less than 600 lb-sorbent/TPD O 2 (tons/day O 2 ) for solid adsorbents, an O 2 /N 2 separation factor greater than 20 for membranes, and O 2 purity greater than 95% at a cost that is projected to be significantly lower than the current state-of-the-art (SOTA) small-scale, commercially available, stand-alone air separation systems. The project team performed a design case for a modular system to produce 10 TPD 95% O 2 and evaluate the cost of O 2 production using such a system.
20 FOSSIL-FUELED POWER PLANTS↗
Potassium permanganate for mercury vapor environmental control
Potassium permanganate (KMnO4) was evaluated for application in removing mercury vapor from exhaust air systems. The KMnO4 may be used in water solution with a liquid spray scrubber system or as a solid adsorber bed material when impregnated onto a zeolite. Air samples contaminated with as much as 112 mg/cu m of mercury were scrubbed to 0.06mg/cum with the KMnO4-impregnated zeolite (molecular sieve material). The water spray solution of permanganate was also found to be as effective as the impregnated zeolite. The KMnO4-impregnated zeolite was applied as a solid adsorber material to (1) a hardware decontamination system, (2) a model incinerator, and (3) a high vacuum chamber for ion engine testing with mercury as the propellant. A liquid scrubber system was also applied in an incinerator system. Based on the results of these experiments, it is concluded that the use of KMnO4 can be an effective method for controlling noxious mercury vapor.
Kuivinen, D. E.↗
Simple Approximation for the Ideal Reference State of Gases Adsorbed on Solid-State Surfaces
Reference states are useful as models for facilitating calculations of equilibrium constants, and they may also serve as standard states that are convenient for organizing and tabulating thermodynamic data; however, standard state conventions and appropriate reference states for adsorbed species have received less attention than those for pure substances and solutes. Here, we compare seven choices of reference states for calculations of equilibrium constants and transition state theory rate constants for flat surfaces, in particular (1) an ideal 2D harmonic oscillator, (2) an ideal rigid-molecule harmonic oscillator, (3) an ideal 2D harmonic oscillator with separable surface modes, (4) a 2D ideal gas, (5) an ideal 2D hindered translator, (6) an ideal 2D hindered translator with lowest-order barriers, and (7) a simple ideal 2D hindered translator proposed in this work. The advantage of models 5–7 is that they can treat both mobile and localized adsorbates in a consistent way, whereas models 1–3 are only appropriate for localized adsorbates, and model 4 is only appropriate for a freely translating adsorbate. Furthermore, models 6 and 7 reduce the computational cost without the user having to calculate barrier heights for diffusion. An advantage of the simple ideal 2D hindered translator is that it has a physical high-temperature limit. We also propose a reference state for nonflat surfaces. Here, the user is encouraged to choose a reference state based on the appropriateness of the model and the practicality of the calculations.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
An assessment of strategies for the development of solid-state adsorbents for vehicular hydrogen storage
We assess the strengths and weaknesses of strategies for creating nanoporous hydrogen storage sorbents.
08 HYDROGEN↗
Efficient Capture and Release of the Rare-Earth Element Neodymium in Aqueous Solution by Recyclable Covalent Organic Frameworks
Rare-earth elements (REEs) are present in a broad range of critical materials. The development of solid adsorbents for REE capture could enable the cost-effective recycling of REE-containing magnets and electronics. In this context, covalent organic frameworks (COFs) are promising candidates for REE adsorption due to their exceptionally high surface area. Despite having attractive physical properties, COFs are heavily underutilized for REE capture applications due to their limited lifecycle in aqueous acidic environments, as well as synthetic challenges associated with the incorporation of ligands suitable for REE capture. Here, in this work, we show how the Ugi multicomponent reaction can be leveraged to postsynthetically modify imine-based COFs for the introduction of a diglycolic acid (DGA) moiety, an efficient scaffold for REE capture. The adsorption capacity of the DGA-functionalized COF was found to be more than 40 times higher than that of the pristine imine COF precursor and more than four times higher than that of the next-best reported DGA-functionalized solid support. This rationally designed COF has appealing characteristics of high adsorption capacity, fast and efficient capture and release of the REE ions, and reliable recyclability, making it one of the most promising adsorbents for solid–liquid REE ion extractions reported to date.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
The Chemistry of CO 2 Capture in an Amine-Functionalized Metal–Organic Framework under Dry and Humid Conditions
In this paper, the use of two primary alkylamine functionalities covalently tethered to the linkers of IRMOF-74-III results in a material that can uptake CO 2 at low pressures through a chemisorption mechanism. In contrast to other primary amine-functionalized solid adsorbents that uptake CO 2 primarily as ammonium carbamates, we observe using solid state NMR that the major chemisorption product for this material is carbamic acid. Finally, the equilibrium of reaction products also shifts to ammonium carbamate when water vapor is present; a new finding that has impact on control of the chemistry of CO 2 capture in MOF materials and one that highlights the importance of geometric constraints and the mediating role of water within the pores of MOFs.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗