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At least 847 records · Page 47
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Sustainable extraction of rare earth elements from coal fly ash leachates using a recyclable ionic liquid

The growing demand for rare earth elements (REEs) has prompted interest in their recovery from alternative sources such as coal fly ash (CFA). This study explores the ionic liquid (IL) betainium bis(trifluoromethylsulfonyl)imide, [Hbet][Tf 2 N], for selective extraction of REEs from leachates of a Class C CFA. While previous studies have demonstrated the effectiveness of using [Hbet][Tf 2 N] to extract REEs from different types of CFA in direct ash-IL systems, this study investigates four CFA leachates prepared using HCl, HNO 3 , H 2 SO 4 , and citrate. Extraction experiments were conducted across varying pH levels and with additives such as ascorbic acid and betaine. Among the systems tested, [Hbet][Tf 2 N] achieved REE recoveries of 51% and 47% from the HCl and citrate leachates, respectively, comparable to 49% REE recovery in ash-IL extraction. Co-extraction of bulk elements was significantly reduced in the leachate-IL systems. Optimal REE extraction occurred near pH 11, and addition of ascorbic acid effectively suppressed iron co-extraction without compromising REE recovery. Recycling experiments demonstrated that [Hbet][Tf₂N] retains its performance over five cycles with manageable losses. These results reveal the promise of [Hbet][Tf 2 N] for effectively recovering REEs from leachates of solid wastes, highlighting its applicability as a sustainable strategy for other aqueous REE feedstocks.

chemistry↗
DOE OSTI2018

Immobilized Gold Nanoparticles Prepared from Gold(III)-Containing Ionic Liquids on Silica: Application to the Sustainable Synthesis of Propargylamines

A cycloaurated phosphinothioic amide gold(III) complex was supported on amorphous silica with the aid of an imidazolium ionic liquid (IL) physisorbed in the SiO2 pores (SiO2–IL) and covalently bonded to the SiO2 (SiO2@IL). Gold(0) nanoparticles (AuNPs) were formed in situ and subsequently immobilized on the SiO2–IL/SiO2@IL phase. The resulting catalytic systems Au–SiO2–IL and Au–SiO2@IL promoted the solvent-free A3 coupling reaction of alkynes, aldehydes, and amines in high yields under solvent-free conditions with very low catalyst loading and without the use of additives. The Au–SiO2@IL catalyst showed good recyclability and could be reused at least five times with yields of propargylamines of ≥80%. This synthetic method provides a green and low cost way to effectively prepare propargylamines. Additionally, 31P high resolution magic angle spinning (HRMAS) NMR spectroscopy is introduced as a simple technique to establish the Au loading of the catalyst.

Soengas, Raquel (ORCID:0000000181780034)↗
DOE OSTI2024

Voltage-induced modulation of interfacial ionic liquids measured using surface plasmon resonant grating nanostructures

We have used surface plasmon resonant metal gratings to induce and probe the dielectric response (i.e., electro-optic modulation) of ionic liquids (ILs) at electrode interfaces. Here, the cross-plane electric field at the electrode surface modulates the refractive index of the IL due to the Pockels effect. This is observed as a shift in the resonant angle of the grating (i.e., Δϕ), which can be related to the change in the local index of refraction of the electrolyte (i.e., Δnlocal). The reflection modulation of the IL is compared against a polar (D2O) and a non-polar solvent (benzene) to confirm the electro-optic origin of resonance shift. The electrostatic accumulation of ions from the IL induces local index changes to the gratings over the extent of electrical double layer (EDL) thickness. Finite difference time domain simulations are used to relate the observed shifts in the plasmon resonance and change in reflection to the change in the local index of refraction of the electrolyte and the thickness of the EDL. Simultaneously using the wavelength and intensity shift of the resonance enables us to determine both the effective thickness and Δn of the double layer. We believe that this technique can be used more broadly, allowing the dynamics associated with the potential-induced ordering and rearrangement of ionic species in electrode–solution interfaces.

Chemistry↗
DOE OSTI2025

Molecular property prediction for very large databases with natural language processing: a case study in ionic liquid design

The prospect of using artificial intelligence (AI) to accurately screen very large databases of compounds for multiple properties has yet to be realized. Here, we explore this possibility using ionic liquids (ILs) which offer unique physicochemical properties and excellent tunability, making them highly versatile solvents for various research applications. Screening millions of potential ILs for the best perfomance for use in specific tasks with experimental methods alone however, is impractical. Further, traditional’ physics-based computational chemistry is hindered by high computational cost. To address this challenge, we leverage a natural language processing (NLP)-based molecular embedding technique with advanced machine learning (ML) models to predict seven key IL properties: viscosity, density, ionic conductivity, surface tension, melting temperature, toxicity, and water solubility. Comprehensive datasets for these properties are obtained, then NLP featurization with Mol2vec is compared with other featurization techniques such as 2D Morgan fingerprints, and 3D quantum chemistry-derived sigma profiles. NLP-based featurization exhibited the best predictive performance, achieving the highest R 2 and lowest RMSE values for all the studied IL properties. Further, we present case studies of how ILs might be screened using combined property criteria for practical cases – lignocellulosic biomass processing, CO 2 capture, and optimal electrolytes for batteries – screening a novel database of ∼10.6 million generated feasible ILs. The results introduce NLP as a powerful tool for engineering many designer solvents with desirable properties for task specific applications.

Mohan, Mood [Oak Ridge National Laboratory (ORNL),↗
DOE OSTI2019

Structure and dynamics of short-chain polymerized ionic liquids

Combining experimental results obtained with X-ray scattering and field-gradient nuclear magnetic resonance (NMR) and an assessment of new and previous dielectric and rheology data, our study focuses on the molecular weight (M w ) evolution of local structure and dynamics in a homologous series of covalently bonded ionic liquids. Performed on a family of electrolytes with a tailored degree of ionic decoupling, this study reveals the differences between monomeric and oligomeric melts with respect to their structural organization, mass and charge transport, and molecular diffusion. Our work demonstrates that for the monomeric compound, the broadband conductivity and mechanical spectra reflect the same underlying distribution of activation barriers and that the Random Barrier Model describes fairly well both the ionic and structural relaxation processes in these materials. Moreover, the oligomers with chains comprising ten segments only exhibit both structural and dynamical fingerprints of a genuine polymer. A comparison of conductivity levels estimated using the self-diffusion coefficients probed via NMR and those probed directly with dielectric spectroscopy reflects the emerging of ion correlations which are affecting the macroscopic charge transport in these materials in a chain-length dependent manner.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Ionic Liquids in Analytical Chemistry: Fundamentals, Technological Advances, and Future Outlook

The development of new analytical methods most often focus on novel materials used to impart selectivity or sensitivity to the protocol. Ionic liquids (ILs) are a class of solvents that have been extensively explored as promising materials for various applications and continue to be explored due to their tunable physicochemical properties. These materials possess melting temperatures below 100 °C and can interact with analytes through a multitude of interactions afforded by their readily tunable chemical structure. These interactions include electrostatic, dispersive, hydrogen bonding, π–π, and dipolar interactions and can be modulated or strengthened based on the functional groups present within the chemical structure. ILs consist predominately of organic cations and either inorganic or organic anions, both of which can be functionalized with desired moieties. Common cation and anions found in IL chemical structures are presented in Figure 1. The unique polarity afforded by the ionic structure has also led to their increasing use in areas including sample preparation, chemical separations, electrochemistry, mass spectrometry, and spectroscopy.

Zeger, Victoria R. [Iowa State Univ., Ames, IA (Un↗
DOE OSTI2025

Is the Chemisorbed CO 2 in Ionic Liquid Electrolytes Active for Electrochemical Utilization? A Case Study on Carboxylate and Carbamate Speciation

This study examines the activity of chemisorbed CO 2 species in the microenvironment formed by bifunctional ionic liquids (ILs) in the reactive capture and conversion (RCC) of CO 2 to CO on silver. Comparative electroanalytical measurements with imidazolium based ILs were performed to probe the impact of electrostatic interactions, anion and cation basicity, and hydrogen bonding on RCC. Particularly, ILs with 1-ethyl-3-methylimidazolium ([EMIM]+) and 1-ethyl-2,3-dimethylimidazolium ([EMMIM]+) cations and aprotic heterocyclic anions of 2-cyanopyrrolide ([2-CNpyr]) and 1,2,4-triazolide ([124-Triz]) were examined for RCC. It was found that anion–CO 2 carbamate complexes facilitate RCC at significantly lower overpotentials compared to cation–CO 2 carboxylate complexes. Additionally, [EMIM]+ was found to better stabilize anion–CO 2 complexes at the interface than [EMMIM]+. Furthermore, it was found that 2-CNpyrH that naturally forms during CO 2 absorption competes for electrode surface adsorption with the anion–CO 2 carbamate complex, thereby reducing the electrochemical activity of the anion–CO 2 complex. These results highlight the importance of IL structure in tuning the interfacial interactions and suggest that ILs with anion-dominated CO 2 chemisorption enhances CO 2 utilization in RCC applications.

Coskun, Oguz Kagan [Case Western Reserve Univ., Cl↗
DOE OSTI2019

Synthesis and Performance of 6FDA-Based Polyimide-Ionenes and Composites with Ionic Liquids as Gas Separation Membranes

Three new isomeric 6FDA-based polyimide-ionenes, with imidazolium moieties and varying regiochemistry ( para-, meta-, and ortho- connectivity), and composites with three different ionic liquids (ILs) have been developed as gas separation membranes. The structural-property relationships and gas separation behaviors of the newly developed 6FDA polyimide-ionene + IL composites have been extensively studied. All the 6FDA-based polyimide-ionenes exhibited good compatibility with the ILs and produced homogeneous hybrid membranes with the high thermal stability of ~380 °C. Particularly, [6FDA I4A pXy][Tf 2 N] ionene + IL hybrids having [C 4 mim][Tf 2 N] and [Bnmim][Tf 2 N] ILs offered mechanically stable matrixes with high CO 2 affinity. The permeability of CO 2 was increased by factors of 2 and 3 for C 4 mim and Bnmim hybrids (2.15 to 6.32 barrers), respectively, compared to the neat [6FDA I4A pXy][Tf 2 N] without sacrificing their permselectivity for CO 2 /CH 4 and CO 2 /N 2 gas pairs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2019

Synthesis and Performance of 6FDA-Based Polyimide-Ionenes and Composites with Ionic Liquids as Gas Separation Membranes

Three new isomeric 6FDA-based polyimide-ionenes, with imidazolium moieties and varying regiochemistry (para-, meta-, and ortho- connectivity), and composites with three different ionic liquids (ILs) have been developed as gas separation membranes. The structural-property relationships and gas separation behaviors of the newly developed 6FDA polyimide-ionene + IL composites have been extensively studied. All the 6FDA-based polyimide-ionenes exhibited good compatibility with the ILs and produced homogeneous hybrid membranes with the high thermal stability of ~380 °C. Particularly, [6FDA I4A pXy][Tf2N] ionene + IL hybrids having [C4mim][Tf2N] and [Bnmim][Tf2N] ILs offered mechanically stable matrixes with high CO2 affinity. The permeability of CO2 was increased by factors of 2 and 3 for C4mim and Bnmim hybrids (2.15 to 6.32 barrers), respectively, compared to the neat [6FDA I4A pXy][Tf2N] without sacrificing their permselectivity for CO2/CH4 and CO2/N2 gas pairs.

Ionenes↗
DOE OSTI2019

Diffusional Dynamics of Tetraalkylphosphonium Ionic Liquid Films Measured by Fluorescence Correlation Spectroscopy

Fluorescence correlation spectroscopy (FCS) is enacted to investigate the diffusional dynamics of hydrophilic (Atto 590) and amphiphilic (DiD) fluorophores in a series of alkylphosphonium ionic liquid (IL) films ([P4448][Cl], [P6668][Cl], [P66614][Cl], and [P66614][NTf2]) in order to determine diffusional parameters and to elucidate nanoscale structural heterogeneities within the IL. From the measured correlation functions, the diffusion coefficients of the fluorescent molecules are estimated, rendering values that span from 0.39-1.2 and 0.146-5.2 µm2/s, for Atto 590 and DiD, respectively. A decrease in the diffusion coefficients is measured as the alkyl chain increases, coincident with a decrease in their viscosity. Interestingly, deviations from the Brownian diffusion behavior of the fluorescent probes in the ILs are observed, showing a time-dependent diffusion coefficient in most of the cases. These deviations can be attributed to the presence of nanoscale structural heterogeneities in the tetraalkylphosphonium ILs. These conclusions validate experimentally the presence of nanosegregation in tetraalkylphosphonium ILs, which has previously been observed in molecular dynamics (MD) studies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Ionic-Liquid-Gating Induced Protonation and Superconductivity in FeSe, FeSe 0.93 S 0.07 , ZrNCl, 1 T -TaS 2 and Bi 2 Se 3 *

We report protonation in several compounds by an ionic-liquid-gating method, under optimized gating conditions. This leads to single superconducting phases for several compounds. Non-volatility of protons allows post-gating magnetization and transport measurements. The superconducting transition temperature T c is enhanced to 43.5 K for FeSe 0.93 S 0.07 , and 41 K for FeSe after protonation. Superconducting transitions with T c ~ 15 K for ZrNCl, ~7.2 K for 1T-TaS 2 , and ~3.8 K for Bi 2 Se 3 are induced after protonation. Electric transport in protonated FeSe 0.93 S 0.07 confirms high-temperature superconductivity. Our 1 H nuclear magnetic resonance (NMR) measurements on protonated FeSe 1- x S x reveal enhanced spin-lattice relaxation rate 1/ 1 T 1 with increasing x , which is consistent with the LDA calculations that H + is located in the interstitial sites close to the anions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Switchable Ionic Liquids: An Environmentally Friendly Medium to Synthesise Nanoparticulate Green Rust

Under anoxic conditions, a novel nanoparticulate green rust with carbonate (nano GR) was synthesized by addition of methanol to degassed switchable ionic liquid (SWIL) solution comprised of 1-hexanol, diazabicycloundec-7-ene (DBU), CO2 and Fe(C2H3O2)2 (Fe(OAc)2). Variable temperature Mössbauer spectroscopy studies indicated the product to be predominantly GR while TEM-SAED method confirmed it be nanoparticulate in nature. Experiments with and without methanol in the SWIL medium suggest that methanol may be responsible for Fe(II) oxidation to Fe(III) necessary for GR formation. Studies with Ar instead of CO2 trigger gas indicated that CO2 is essential for GR formation. Conditions to generate CO32- anion was most likely provided by basic environment of the medium. The nano GR suspension was very reactive and instantaneously oxidized completely to a reddish-brown precipitate upon exposure to ambient atmosphere. The nature of the oxidized sample is not certain. The oxidized product, however, appears to be a mix of ferric green rust- [GR(CO32-]*; major] and ferrihydrite-like minerals. To our knowledge, this is first report of use of environmentally-friendly SWIL reagents to synthesize very reactive nano GR materials.

Lao, David↗
DOE OSTI2022

Ion Correlations and Partial Ionicities in the Lamellar Phases of Block Copolymeric Ionic Liquids

Recently, significant interest has arisen on the impact of dynamical ion correlations on the conductivity and transport properties of polymeric electrolyte materials. It has been hypothesized that confining ion motion to narrow channels may reduce such ion correlations and enhance the resulting ionic conductivity. Motivated by such considerations, in this study we used a multiscale simulation framework to study the dynamical ion correlations in the microphase-separated lamella phase of block copolymeric ionic liquids and compare with the corresponding results for homopolymeric systems. We probed the influence of ion correlations through the partial ionicity, Δ, which quantifies the ratio of true conductivity to the ideal, Nernst–Einstein conductivity for the anion-related contributions. Consistent with our original hypothesis, our results demonstrate that the partial ionicity relating to the mobile anions is much larger in the lamella phases of block copolymers compared to that in homopolymers. Analysis of the distinct conductivity contributions demonstrates that such results arise as a result of an intricate compensation among the nonideal dynamical correlations relating to anions in lamella phases. Overall, our results suggest that self-assembled phases of block copolymers may provide an avenue to tune the dynamical ion correlations in polymer electrolyte systems.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Performance Analysis of a Membrane-based Ionic Liquid Desiccant (ILD) Dehumidifier

Air dehumidification through cooling is an energy-intensive process, which consumes about 20-40% of the overall energy for air-conditioning. Liquid desiccant dehumidification can separate dehumidification from space cooling and has potential to improve the cooling efficiency and reduce the overall energy consumption for air-conditioning. However, the drawbacks such as liquid carryover and corrosion, membrane contamination and blocking, limit its application. To eliminate these problems, a new dehumidifier using nonporous membrane and ionic liquid desiccant (ILD) was developed. The dehumidification performance of the new dehumidifier was characterized through a series of lab tests. Test results indicate that the new dehumidifier can achieve a moisture removal rate up to 180.3 g/h and a dehumidification effectiveness up to 12.7%. A parametric study found that the dehumidification performance is sensitive to the flowrates of the air and the ILD solution. A higher mass flow ratio between the ILD solution and the air could result in better dehumidification performance.

Wang, Lingshi↗
DOE OSTI2021

Engineering the Interlayer Spacing by Pre-Intercalation for High Performance Supercapacitor MXene Electrodes in Room Temperature Ionic Liquid

MXenes exhibit excellent capacitance at high scan rates in sulfuric acid aqueous electrolytes, but the narrow potential window of aqueous electrolytes limits the energy density. Organic electrolytes and room-temperature ionic liquids (RTILs) can provide higher potential windows, leading to higher energy density. The large cation size of RTIL hinders its intercalation in-between the layers of MXene limiting the specific capacitance in comparison to aqueous electrolytes. In this work, different chain lengths alkylammonium (AA) cations are intercalated into Ti 3 C 2 T x , producing variation of MXene interlayer spacings (d-spacing). AA-cation-intercalated Ti 3 C 2 T x (AA-Ti 3 C 2 ), exhibits higher specific capacitances, and cycling stabilities than pristine Ti 3 C 2 T x in 1 m 1-ethly-3-methylimidazolium bis-(trifluoromethylsulfonyl)-imide (EMIMTFSI) in acetonitrile and neat EMIMTFSI RTIL electrolytes. Pre-intercalated MXene with an interlayer spacing of ≈2.2 nm, can deliver a large specific capacitance of 257 F g –1 (1428 mF cm –2 and 492 F cm –3 ) in neat EMIMTFSI electrolyte leading to high energy density. Quasi elastic neutron scattering and electrochemical impedance spectroscopy are used to study the dynamics of confined RTIL in pre-intercalated MXene. Furthermore, molecular dynamics simulations suggest significant differences in the structures of RTIL ions and AA cations inside the Ti 3 C 2 T x interlayer, providing insights into the differences in the observed electrochemical behavior.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Functionalization of Electrodes with Tunable [EMIM] x [Cl] x +1 – Ionic Liquid Clusters for Electrochemical Separations

Functionalization of electrodes with clusters of hydrophobic molecules may improve the energy efficiency and selectivity of electrochemical separations by modulating the desolvation process occurring at the interface. Ionic liquids (IL), which have a broad range of compositions and properties, are potential candidates for controlling the transport, desolvation, and adsorption of target ions at electrochemical interfaces. We report a joint experimental and theoretical investigation of the structure, stability, and selective adsorption properties of the IL clusters 1-ethyl-3-methylimidazolium chloride [EMIM] x [Cl] x+1 - (x = 1 – 10) and demonstrate their ability to adsorb and separate ions from solution. The structure and stability of the IL clusters are determined experimentally using high-mass-resolution electrospray ionization mass spectrometry, collision-induced dissociation, and negative ion photoelectron spectroscopy. Global optimization theory and ab initio molecular dynamics simulations provide molecular-level insight into the bonding and structural fluxionality of these species. Ion soft landing is used to selectively functionalize the surface of highly oriented pyrolytic graphite (HOPG) working electrodes with [EMIM] 1 [Cl] 2 - , [EMIM] 3 [Cl] 4 - , and [EMIM] 5 [Cl] 6 - clusters. Kelvin probe microscopy provides insight into the relative stability of the clusters on HOPG and their effect on the work function of IL-functionalized electrodes. Cyclic voltammetry measurements reveal irreversible adsorption of Fe(CN) 6 4-/3- anions during redox cycling, while electrochemical impedance spectroscopy indicates a substantial decrease in the electron transfer resistance of the IL-functionalized electrodes due to adsorption of Fe(CN) 6 4-/3- . Overall, our findings demonstrate that IL clusters with different size and stoichiometry may be used to increase the efficiency of electrochemical separations, opening new horizons in selective electrode functionalization.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗