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Williams, Neil J.

Publications and source records attributed to Williams, Neil J..

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Near Quantitative Removal of Selenate and Sulfate Anions from Wastewaters by Cocrystallization with Chelating Hydrogen-Bonding Guanidinium Ligands

Selenium (Se) has become an environmental contaminant of aquatic ecosystems as a result of human activities, particularly mining, fossil fuel combustion, and agricultural activities. By leveraging the high sulfate concentrations relative to Se oxyanions (i.e., SeO n 2– , n = 3, 4) present in some wastewaters, we have developed an efficient approach to Se-oxyanion removal by cocrystallization with bisiminoguanidinium (BIG) ligands that form crystalline sulfate/selenate solid solutions. The crystallization of the sulfate, selenate and selenite, oxyanions and of sulfate/selenate mixtures with five candidate BIG ligands are reported along with the thermodynamics of crystallization and aqueous solubilities. Oxyanion removal experiments with the top two performing candidate ligands show a near quantitative removal (>99%) of sulfate or selenate from solution. When both sulfate and selenate are present, there is near quantitative removal (>99%) of selenate, down to sub-ppb Se levels, with no discrimination between the two oxyanions during cocrystallization. Reducing the selenate concentrations by 3 orders of magnitude or more relative to sulfate, as found in many wastewaters, led to no measurable loss in Se removal efficiencies. This work offers a simple and effective alternative to selective separation of trace amounts of highly toxic selenate oxyanions from wastewaters, to meet stringent regulatory discharge limits.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Dialing in Direct Air Capture of CO 2 by Crystal Engineering of Bis-iminoguanidines

Direct air capture (DAC) technologies that extract carbon dioxide from the atmosphere via chemical processes have the potential to restore the atmospheric CO 2 concentration to an optimal level. This study elucidates structure-property relationships in DAC by crystallization of bis-iminoguanidine (BIG) carbonate salts. Here, their crystal structures are analyzed by X-ray and neutron diffraction to accurately measure key structural parameters including molecular conformations, hydrogen bonding, and π-stacking. Experimental measurements of key properties, such as aqueous solubilities and regeneration energies and temperatures, are complemented by first-principles calculations of lattice and hydration free energies, as well as free energies of reactions with CO 2 , and BIG regenerations. Minor structural modifications in the molecular structure of the BIGs are found to result in major changes in the crystal structures and the aqueous solubilities within the series, leading to enhanced DAC.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Guanidine compounds for removal of oxyanions from aqueous solutions and for carbon dioxide capture

Methods for removing oxyanions from water according to the following steps: (i) dissolving an oxyanion precipitating compound into the aqueous source to result in precipitation of an oxyanion salt of the oxyanion precipitating compound; and (ii) removing the oxyanion salt from the water containing the oxyanion to result in water substantially reduced in concentration of the oxyanion; wherein the oxyanion precipitating compound has the following composition: wherein A is a ring-containing moiety and Xm− is an anionic species with a magnitude of charge m. The invention employs bis-iminoguanidinium compounds according to Formula (1a) as well as neutral precursor compounds according to Formula (1), which can be used for removing undesirable species from aqueous solutions or air, such as removal of sulfate from water and carbon dioxide from air.

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

Direct Air Capture of CO 2 with Aqueous Amino Acids and Solid Bis-iminoguanidines (BIGs)

We report a bench-scale direct air capture (DAC) process comprising CO 2 absorption with aqueous amino acid salts (i.e., potassium glycinate, potassium sarcosinate), followed by room-temperature regeneration of the amino acids by reaction with solid meta-benzene-bis(iminoguanidine) (m-BBIG), resulting in crystallization of the hydrated m-BBIG carbonate salt, (m-BBIGH 2 )(CO 3 )(H 2 O) n (n = 3–4). The CO 2 is subsequently released by mild heating (60–120 °C) of the carbonate crystals, which regenerates the m-BBIG solid quantitatively. This low-temperature crystallization-based DAC process circumvents the need to heat the aqueous amino acid sorbents, thereby minimizing their loss through thermal and oxidative degradation. The CO 2 cyclic capacity for the sarcosine/m-BBIG system, measured over three consecutive absorption/regeneration cycles, is in the range of 0.12–0.20 mol/mol. The regeneration energy of m-BBIG, comprising the enthalpy of CO 2 and water release, and the sensible heat, is 360 kJ/mol (8.2 GJ/ton CO 2 ). Alternatively, the aqueous amino acids can be regenerated by boiling under reflux, with measured cyclic capacities of up to 0.64 mol/mol.

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

Energy-Efficient CO 2 Capture from Flue Gas by Absorption with Amino Acids and Crystallization with a Bis-Iminoguanidine

In this work, we report a hybrid solvent/solid-state approach to CO 2 separation from flue gas, consisting of absorption with aqueous glycine or sarcosine amino acids, followed by crystallization of the bicarbonate salt of glyoxal-bis(iminoguanidine) (GBIG), and subsequent solid-state CO 2 release from the bicarbonate crystals. In this process, the GBIG bicarbonate crystallization regenerates the amino acid sorbent at ambient temperature, and the CO 2 is subsequently released by mild heating (120 °C) of the GBIG bicarbonate crystals, which results in quantitative regeneration of GBIG. The cyclic capacities measured from multiple absorption–regeneration cycles are in the range of 0.2–0.3 mol CO 2 /mol amino acid. The regeneration energy of this hybrid solvent/solid-state approach is 24% and 40% lower than the regeneration energy of benchmark industrial sorbents monoethanolamine and sodium glycinate, respectively. Lastly, as the amino acid sorbent is never heated in the hybrid process, its loss through evaporation or degradation is minimized.

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

CO 2 Capture Going BIG

“Currently, the world is way off track in meeting the Paris Agreement climate goals. It cannot get back on track without CCS”. This statement, issued by the Global CCS Institute in its recent report on The Global Status of CCS (Carbon Capture and Storage), underlines the importance of developing new methods and technologies to reduce the amount of greenhouse gases in the atmosphere. Since the beginning of the industrial revolution, the atmospheric CO 2 concentration has increased from 280 to 410 parts per million (ppm), which is a 46% increase. Most of the added CO 2 can be attributed to fossil fuel emissions from energy production (i.e., burning coal, natural gas, and oil) and other industries (e.g., cement, steel). The CO 2 level will likely continue to rise in the coming decades, as the world population and the energy consumption continue to increase and rely on fossil fuels. While the Earth’s ecosystems have mechanisms for reducing the amounts of CO 2 present in the atmosphere, absorbing roughly half of our annual emissions, the other half, consisting of about 18 gigatonnes of carbon dioxide per year, will have to be addressed through CCS technologies. At the same time, the global average temperature has already risen about 1 °C over the course of the 20th century, and will likely exceed the 1.5 °C increase limit in a few decades. Undeniably, as the Earth is out of energy balance with the current atmospheric composition, there is more warming in the pipeline even if the global emissions were to be cut to zero today. A recent report from the U.S. National Academy of Sciences concluded that limiting the increase in the global temperature to less than 2 °C by the end of this century becomes exceedingly challenging without large-scale deployment of Negative Emissions Technologies (NETs). NETs, such as Direct Air Capture (DAC), remove CO 2 out of the atmosphere, in effect reducing past emissions. They also can address dispersed emissions from transportation and buildings, which currently account to about 50% of global annual emissions.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2019

Enhancing selectivity of cation exchange with anion receptors

Here, we introduce a new supramolecular strategy where an anion receptor modifies the selectivity ligands for cations. This is demonstrated by combining the classic anion receptor calix[4]pyrrole (C4P) and a phenolic ligand, which leads to remarkable enhancement in selectivity for Cs + over Na + . Crystal structures and molecular simulations confirmed the persistent formation of ion-pair C4P–Cs + –phenolate complexes, while the smaller Na + ion cannot efficiently interact.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Peroxide-treated metal-organic framework templated adsorbents for remediation of high level nuclear waste

Remediation of legacy nuclear waste is one of the greatest challenges faced by the US Department of Energy, with projected cleanup efforts requiring over five decades and hundreds of billions of dollars. New materials are necessary to accelerate waste processing, achieving time and financial savings. Herein we report a peroxide treatment to a Ti metal-organic framework (MOF) and related MOF-templated adsorbents. Furthermore, the resulting materials displayed exceptional affinity for Am(III), achieving distribution coefficients in excess of 10 5 mL/g, and out-performing state-of-the-art benchmarks monosodium titanate (MST) and peroxo-treated modified MST (mMST) for removal of 85 Sr(II) and 239, 240 Pu(IV) from legacy nuclear waste simulant.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Surprisingly selective sulfate extraction by a simple monofunctional di(imino)guanidinium micelle-forming anion receptor

Here, we report a novel di(imino)guanidinium anion extractant with unparalleled selectivity for sulfate in a liquid–liquid separation system. In addition to a 4.4 order-of-magnitude enhancement in affinity compared to a standard benchmark, our alkylated di(imino)guanidinium receptor is economically synthesized and features good compatibility with application-relevant aliphatic solvents. Small-angle X-ray scattering results reveal the formation of reverse-micelles, which together with the significant organic-phase water content challenge traditional notions of selectivity in extraction of superhydrophilic anions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Selective Solid–Liquid and Liquid–Liquid Extraction of Lithium Chloride Using Strapped Calix[4]pyrroles

Abstract LiCl is a classic “hard” ion salt that is present in lithium‐rich brines and a key component in end‐of‐life materials (that is, used lithium‐ion batteries). Its isolation and purification from like salts is a recognized challenge with potential strategic and economic implications. Herein, we describe two ditopic calix[4]pyrrole‐based ion‐pair receptors ( 2 and 3 ), that are capable of selectively capturing LiCl. Under solid–liquid extraction conditions, using 2 as the extractant, LiCl could be separated from a NaCl/KCl salt mixture containing as little as 1 % LiCl with circa 100 % selectivity, while receptor 3 achieved similar separations when the LiCl level was as low as 200 ppm. Under liquid–liquid extraction conditions using nitrobenzene as the non‐aqueous phase, the extraction preference displayed by 2 is KCl>NaCl>LiCl. In contrast, 3 exhibits high selectivity towards LiCl over NaCl and KCl, with no appreciable extraction being observed for the latter two salts.

He, Qing↗
DOE OSTI2018

Selective Solid-liquid Extraction and Liquid-liquid Extraction of Lithium Chloride using Strapped Calix[4]pyrroles

LiCl is a classic "hard" ion salt that is present in lithium-rich brines and a key component in end-of-life materials (i.e., used lithium-ion batteries). Its isolation and purification from like salts is a recognized challenge with potential strategic and economic implications. Here in this paper, we describe two ditopic calix[4]pyrrole-based ion pair receptors (2 and 3), that are capable of selectively capturing LiCl. Under solid-liquid extraction conditions, using 2 as the extractant, LiCl could be separated from a NaCl-KCl salt mixture containing as little as 1% LiCl with ~100% selectivity, while receptor 3 achieved similar separations when the LiCl level was as low as 200 ppm. Under liquid-liquid extraction conditions using nitrobenzene as the non-aqueous phase, the extraction preference displayed by 2 is KCl > NaCl > LiCl. Lastly, in contrast, 3 exhibits high selectivity towards LiCl over NaCl and KCl, with no appreciable extraction being observed for the latter two salts.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Direct air capture of CO 2 via aqueous-phase absorption and crystalline-phase release using concentrated solar power

Using negative emissions technologies for the net removal of greenhouse gases from the atmosphere could provide a pathway to limit global temperature rises. Direct air capture of carbon dioxide offers the prospect of permanently lowering the atmospheric CO 2 concentration, providing that economical and energy-efficient technologies can be developed and deployed on a large scale. Here in this paper, we report an approach to direct air capture, at the laboratory scale, using mostly off-the-shelf materials and equipment. First, CO 2 absorption is achieved with readily available and environmentally friendly aqueous amino acid solutions (glycine and sarcosine) using a household humidifier. The CO 2 -loaded solutions are then reacted with a simple guanidine compound, which crystallizes as a very insoluble carbonate salt and regenerates the amino acid sorbent. Finally, effective CO 2 release and near-quantitative regeneration of the guanidine compound are achieved by relatively mild heating of the carbonate crystals using concentrated solar power.

14 SOLAR ENERGY↗
DOE OSTI2017

Simple guanidinium motif for the selective binding and extraction of sulfate

A simple bidentate anion receptor, shown previously to adopt a rigid pseudobicyclic conformation while binding anions in the solid state, selectively binds sulfate in aqueous solutions with log K 1 and log K 2 values of 3.78 ± 0.12 M-1 and 2.10 ± 0.23 M-1, respectively. This anion receptor has little to no affinity for nitrate and chloride in the same solutions. A lipophilic derivative was synthesized in four steps to yield an extractant that is capable of partitioning sulfate into 1,2 dichloroethane from water in the presence of large excesses of chloride. This extractant demonstrated D values as high as 2.5 with only 30 mM of anion receptor.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Capping the calix: How toluene completes cesium( i ) coordination with calix[4]pyrrole

The role of solvent in molecular recognition systems is under-researched and often ignored, especially when the solvent is considered “non-interacting”. This study concerns the role of toluene solvent in cesium(I) recognition by calix[4]pyrrole. We show that π-donor interactions bind toluene molecules onto the open face of the cation-receptor complex, thus “capping the calix.” As a result, by characterizing this unusual aromatically-saturated complex, we show how “non-interacting” aromatic solvents can directly coordinate receptor-bound cations and thus influence recognition.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Selective separation of americium from europium using 2,9-bis(triazine)-1,10-phenanthrolines in ionic liquids: a new twist on an old story

Bis-triazine phenanthrolines have shown great promise for f-block metal separations, attributable to their highly preorganized structure, nitrogen donors, and more enhanced covalent bonding with actinides over lanthanides. However, their limited solubility in traditional solvents remains a technological bottleneck. Here in this paper we report our recent work using a simple 2,9-bis(triazine)-1,10-phenanthroline (Me-BTPhen) dissolved in an ionic liquid (IL), demonstrating the efficacy of IL extraction systems for the selective separation of americium from europium, achieving separation factors in excess of 7500 and selectively removing up to 99% of the americium. Characterization of the coordination environment was performed using a combination of X-ray absorption fine structure spectroscopy (XAFS) and density functional theory (DFT) calculations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗