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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS2022

Remote Sensing of Aerosol Water Fraction, Dry Size Distribution and Soluble Fraction Using Multi-Angle, Multi-Spectral Polarimetry

A framework to infer volume water fraction, soluble fraction and dry size distributions of fine mode aerosol from multi-angle, multi-spectral polarimetry retrievals of column-averaged ambient aerosol properties is presented. The method is applied to observations of the Research Scanning Polarimeter (RSP) obtained during two NASA aircraft campaigns, namely the Aerosol Cloud meTeorology Interactions oVer the western ATlantic Experiment (ACTIVATE) and the Cloud, Aerosol, and Monsoon Processes-Philippines Experiment (CAMP2Ex). All aerosol retrievals are statistically evaluated using in situ data. Volume water fraction is inferred from the retrieved ambient real part of the refractive index, assuming a dry refractive index of 1.54 and by applying a volume mixing rule to obtain the effective ambient refractive index. The uncertainties in inferred volume water fraction resulting from this simplified model are discussed and estimated to be lower than 0.2 and decreasing with increasing volume water fraction. The daily mean retrieved volume water fractions correlate well with the in situ values with a mean absolute difference of 0.09. Polarimeter-retrieved ambient effective radius for daily data is shown to increase as a function of volume water fraction as expected. Furthermore, the effective variance of the size distributions also increases with increasing effective radius, which we show is consistent with an external mixture of soluble and insoluble aerosol. The relative variations of effective radius and variance over an observation period are then used to estimate the soluble fraction of the aerosol. Daily results of soluble fraction correlate well with in situ observed sulfate mass fraction with a correlation coefficient of 0.79. Subsequently, inferred water and soluble fractions are used to derive dry fine-mode size distributions from their ambient counterparts. While dry effective radii obtained in situ and from RSP show similar ranges, in situ values are generally substantially smaller during the ACTIVATE deployments, which may be due to biases in RSP retrievals or in the in situ observations, or both. Both RSP and in situ observations indicate the dominance of aerosol with low hygroscopicity during the ACTIVATE and CAMP2Ex campaigns. Furthermore, RSP indicates a high degree of external mixing of particles with low and high hygroscopicity. These retrievals of fine mode water volume fraction and soluble fraction may be used for the evaluation of water uptake in atmospheric models. Furthermore, the framework allows to estimate the variation in the concentration of fine-mode aerosol larger than a specific dry radius limit, which can be used as a proxy for the variation in cloud condensation nucleus concentrations. This framework may be applied to multi-angle, multi-spectral satellite data expected to be available in the near future.

Bastiaan Van Diedenhoven↗
DOE OSTI2018

Estimation of the Temperature-Dependent Nitrogen Solubility in Stainless Fe-Cr-Mn-Ni-Si-C Steel Melts During Processing

The influence of chemical composition, temperature, and pressure on the nitrogen solubility of various high alloy stainless steel grades, namely Fe-14Cr-(0.17-7.77)Mn-6Ni-0.5Si-0.03C [wt pct], Fe-15Cr-3Mn-4Ni-0.5Si-0.1C [wt pct], and Fe-19Cr-3Mn-4Ni-0.5Si-0.15C [wt pct], was studied in the melt. The temperature-dependent N-solubility was determined using an empirical approach proposed by Wada and Pehlke. The thus calculated N-concentrations overestimate the actual N-solubility of all the studied Fe-Cr-Mn-Ni-Si-C steel melts at a given temperature and pressure. Consequently, the calculation model has to be modified by Si and C because both elements are not recognized in the original equation. The addition of the 1st and 2nd order interaction parameters for Si and C to the model by Wada and Pehlke allows a precise estimation of the temperature-dependent nitrogen solubility in the liquid steel bath, and fits very well with the measured nitrogen concentrations during processing of the steels. Moreover, the N-solubility enhancing effect of Cr- and Mn-additions has been demonstrated.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Thermodynamic Study on MgO Solubility in High-Alumina-Content Slag System

In the current study, the MgO solubility in molten slag was measured to clarify the effect of basicity and Al{sub 2}O{sub 3} content on the MgO solubility equilibrating with the spinel solid phase in the CaO-SiO{sub 2}-Al{sub 2}O{sub 3} system. The MgO solubility decreased with the increasing basicity of the slag. However, the MgO solubility in the spinel equilibrium region exhibited different dependence when compared with the basicity dependence in the MgO equilibrium region. The aforementioned experimental results were quantitatively analyzed using magic-angle spinning (MAS) {sup 27}Al nuclear magnetic resonance (NMR) spectroscopy, in which the fraction of Al ions in the slag of spinel equilibrium region was changed to 4, 5, and 6. In addition, the analysis of the degree of Al avoidance modeling indicated that the change in bridging oxygen (BO) linkage species (distinguished into Al-O-Al, Si-O-Si, and Al-O-Si) was based on the Al/Si ratio change. The aforementioned change in BO linkage species led to a change in the MgO solubility with the stability of the alumina. Thus, the spinel equilibrium dissolution mechanism is discussed in detail in terms of the thermodynamic and structural influence in molten slag.

36 MATERIALS SCIENCE↗
DOE OSTI2024

High-throughput measurements of CO 2 permeance and solubility in ionic liquid reveal a synergistic role of ionic interactions and void fractions

The factors that govern CO 2 solubility in ionic liquids (ILs) are of great interest for the development of new materials for CO 2 capture and utilization. The cationic functional group (i.e., imidazolium, pyrrolidinium, pyridinium, etc.), alkyl chain length of cation, degree of fluorination of anion, anion size, and the void fraction in IL are known to influence CO 2 solubility. However, a comprehensive explanation of how these factors collectively affect CO 2 solubility has not been developed yet. This knowledge gap is largely attributed to the lack of CO 2 solubility data for IL structures other than imidazolium based ILs. We report here an automated high-throughput (HT) setup for the measurement of CO 2 solubility in room-temperature ILs (RTILs) combining six different anions and nine different cations for a total of 19 different specific ranges of RTILs. The HT setup first dispenses up to 200 µL of RTILs in a 96-well microtiter plate and then utilizes a robotic arm to measure cyclic voltammogram (CV) in each well using maneuverable Ag electrodes. The Cottrell analysis of the CO 2 reduction CV peak provides a direct measurement of CO 2 permeance in RTILs, which yields Henry’s constant from the estimated diffusion coefficient of CO 2 . Henry’s constants thus obtained are in very good agreement with those reported earlier. The measured CO 2 permeance and Henry’s constant of all RTILs seem to follow a first-order dependence on void fraction and a second-order dependence on electrostatic interaction between anion and cation of IL, with some synergistic dependence on the product of a void fraction and electrostatic interaction, making them two important descriptors for the design of novel ILs.

CO2 Solubility↗
DOE OSTI2017

Solubilities of six lithium salts in five non-aqueous solvents and in a few of their binary mixtures

Solubilities were measured from 25 to 45 °C for six lithium salts (LiF, LiCl, LiBr, LiNO 3 , LiTFSI and LiPF 6 ) in five pure non–aqueous solvents (ethanol, acetonitrile, dimethyl carbonate, dimethyl sulfoxide and propylene carbonate) and in a few of their binary mixtures (ethanol + DMSO, DMC + DMSO and DMC + PC). The experimental method uses a Varian inductively–coupled plasma–optical–emission spectrometer (ICP–OES). Solubilities increase with rising temperature. At a given temperature, LiNO 3 shows the highest solubility in all solvents. Salt solubilities follow the order LiNO 3 > LiTFSI > LiBr > LiCl > LiPF 6 > LiF. The dissolving abilities of the solvents are in the order ethanol > DMSO > acetonitrile > PC > DMC. Finally, coupled with the salt's melting temperature and enthalpy of fusion, liquid–phase activity coefficients for salts were obtained from the solubility data.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

The solubility and speciation of REE phosphate endmembers (CePO 4 and YPO 4 ) in Cl-rich aqueous fluids from 350 to 450 °C and implications for natural systems

The rare earth elements (REE) are important metals used increasingly in advanced technologies. Within the crust, the elements Ce and Y are commonly more abundant compared to other lanthanides and comprise important end-member constituents of REE-bearing minerals. Specifically, Ce is part of the light (L) REE which have larger ionic radii than the heavy (H) REE, which are grouped together with Y. These differences in ionic radius can lead to important physico-chemical trends within the lanthanide group. Despite a recent increase in experimental and thermodynamic data for the REE at high temperature and pressure, there is still a significant lack of these data at supercritical conditions. In this study we conducted batch-type experiments to measure the solubility of REE phosphates (CePO 4 and YPO 4 ) at varying starting pH (1.5–10), and salinity (0.01–1.4 mol/kg NaCl) at 350 and P sat , and from 400 to 450 °C at 700 bar. Results show that the solubility of Ce (33–0.14 ppb) is generally higher than Y (13–0.13 ppb) and that Ce complexes more strongly with both chloride and hydroxyl ligands compared to Y. The solubilities of both REE phosphates are highly pH-dependent and, to a lesser extent, depend on salinity at the studied conditions. The solubility data from this study were implemented into the GEMSFITS program to optimize the thermodynamic properties of Ce and Y hydroxyl and chloride species. The updated standard partial molal Gibbs energies of formation (Δ f G 0 T,P ) are used within the experimental temperature and pressure range to accurately predict the CePO 4 and YPO 4 solubility and Ce and Y speciation behavior. Based on the updated thermodynamic properties we also provide formation constants (log β n Cl,OH ) for Ce and Y hydroxyl and chloride species. Updated thermodynamic properties are applied to model REE-apatite dissolution and REE mobility based on the Pea Ridge iron oxide apatite deposit in Missouri, USA. The apatite dissolution model replicates natural observations including the replacement of monazite and xenotime after apatite and is an example of the utility of the new thermodynamic constants applied to supercritical crustal fluids. Furthermore, the findings of this study advance the predictive capabilities of geochemical models, our understanding of the behavior of individual REE, and permit modeling the overarching fractionation trends between LREE and HREE in supercritical crustal fluids.

58 GEOSCIENCES↗
DOE OSTI2011

Conductive methyl blue-functionalized reduced graphene oxide with excellent stability and solubility in water

Graphical abstract: MB-rGO was synthesized by making use of {pi} stacking and water-solubility of MB to assist the hydrazine mediated reduction of graphene oxide (GO) in aqueous solution. The resulting MB-rGO shows excellent solubility and stability in aqueous solution, and the electrical conductivity of MB-rGO is almost two orders of magnitude larger than that of GO. Highlights: Black-Right-Pointing-Pointer Methyl blue (MB) stacks onto the plane of reduced graphene oxide (rGO) by strong {pi}-{pi} interactions. Black-Right-Pointing-Pointer Sulfo groups of MB prevent rGO from aggregating by electrostatic and steric repulsions. Black-Right-Pointing-Pointer MB-functionalized rGO (MB-rGO) shows excellent solubility and stability in aqueous solution. Black-Right-Pointing-Pointer Electrical conductivity of MB-rGO is almost two orders of magnitude larger than that of GO. -- Abstract: {pi} stacking and water-solubility of methyl blue (MB) are expected to facilitate the hydrazine mediated reduction of graphene oxide (GO) in aqueous environment. Our newly obtained MB-functionalized reduced graphene oxide (MB-rGO) exhibited excellent solubility and stability in water. The results showed that the MB molecules stacked non-covalently onto the basal plane of rGO while the sulfo groups of MB prevented the rGO from aggregation. In addition, the better electrical conductivity of MB-rGO than that of GO was analyzed. This novel conductive MB-rGO should have promising applications in diverse nanotechnological areas, such as electronic and optoelectronic devices, photovoltaics, sensors, and microfabrication.

36 MATERIALS SCIENCE↗
DOE OSTI2016

The impacts of surface polarity on the solubility of nanoparticle

In order to study the dependence of water solubility and hydration behavior of nanoparticles on their surface polarity, we designed polar nanoparticles with varying surface polarity by assigning atomic partial charge to the surface of C60. The water solubility of the nanoparticle is enhanced by several orders of magnitude after the introduction of surface polarity. Nevertheless, when the atomic partial charge grows beyond a certain value (q{sub M}), the solubility continuously decreases to the level of nonpolar nanoparticle. It should be noted that such q{sub M} is comparable with atomic partial charge of a variety of functional groups. The hydration behaviors of nanoparticles were then studied to investigate the non-monotonic dependence of solubility on the surface polarity. The interaction between the polar nanoparticle and the hydration water is stronger than the nonpolar counterpart, which should facilitate the dissolution of the nanoparticles. On the other hand, the surface polarity also reduces the interaction of hydration water with the other water molecules and enhances the interaction between the nanoparticles which may hinder their dispersion. Besides, the introduction of surface polarity disturbs and even rearranges the hydration structure of nonpolar nanoparticle. Interestingly, the polar nanoparticle with less ordered hydration structure tends to have higher water solubility.

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

Computational Studies of Solubilities of LiO 2 and Li 2 O 2 in Aprotic Solvents

Knowledge of the solubilities of Li 2 O 2 and LiO 2 in aprotic solvents is important for insight into the discharge and charge processes of Li-O 2 batteries, but these quantities are not well known. In this contribution, the solvation free energies of molecular LiO 2 and Li 2 O 2 in various organic solvents were calculated using various explicit and implicit solvent models, as well as ab initio molecular dynamics (AIMD) methods. Best estimates for the solvation energies from these calculations along with calculated lattice energies of Li 2 O 2 and LiO 2 were used to determine the solubility of bulk LiO 2 and Li 2 O 2 . The computed solubility of LiO 2 (1.8 × 10 -2 M) is about 15 orders higher than that of Li 2 O 2 (2.0 × 10 -17 M) due to a much less negative lattice energy of bulk LiO 2 compared to that of Li 2 O 2 . The difference in solubilities between LiO 2 and Li 2 O 2 likely will affect the nucleation and growth mechanisms and resulting morphologies of the products formed during battery discharge, influencing the performance of the battery cell. In conclusion, the calculated LiO 2 and Li 2 O 2 solubilities provide important information for fundamental studies of discharge and charge chemistries in Li-O 2 batteries.

25 ENERGY STORAGE↗
DOE OSTI2013

Evaluation of the Role of Cisplatin-conjugated-soluble Gelatin Sponge: Feasibility Study in a Swine Model

PurposeTo evaluate the safety and the delivery function of cisplatin-conjugated-soluble gelatin sponge in a swine model.MethodsFifteen healthy young swine were assigned into three groups: transarterial cisplatin infusion group, transarterial chemoembolization (TACE) with cisplatin-conjugated 120-min soluble gelatin sponge (TACE-120) group, and TACE with cisplatin-conjugated 360-min soluble gelatin sponge (TACE-360) group. A total volume of 0.8 mL/kg cisplatin in each group and 8 mg/kg soluble gelatin sponge in TACE-120 and TACE-360 groups were injected from the left hepatic artery in small increments for 10 min. Common hepatic angiography and whole-blood sampling via the left hepatic vein were conducted to explore recanalization immediately after the procedure and again at 10, 30, 60, 90, 120, 180, 240, 300, 360, and 420 min later. The area under the plasma concentration curve (AUC) of non-protein-bound platinum was compared among the three groups. Each liver was removed and cut into 10-cm-thick sections for calculating liver-damaged volume ratio.ResultsSequential angiography depicted gradual recanalization of the occluded hepatic artery and total recanalization at 120 and 360 min after embolization in the TACE-120 and TACE-360 groups, respectively. Of the three groups, AUC{sub 0-30}, AUC{sub 30-120}, and AUC{sub 120-420} were significantly highest in the transarterial cisplatin infusion group (p < 0.001), the TACE-120 group (p < 0.001), and the TACE-360 group (p < 0.001), respectively. The liver-damaged volume ratio in the TACE-360 group was small (8.20 %) but significantly higher than that in the TACE-120 group (2.67 %, p = 0.014).ConclusionCisplatin-conjugated soluble gelatin sponge functions as a cisplatin carrier and is associated with tolerable liver damage.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2016

Solubility constants of hydroxyl sodalite at elevated temperatures evaluated from hydrothermal experiments: Applications to nuclear waste isolation

In this study, solubility constants of hydroxyl sodalite (ideal formula, Na 8 [Al 6 Si 6 O 24 ][OH] 2 ·3H 2 O) from 25°C to 100°C are obtained by applying a high temperature Al—Si Pitzer model to evaluate solubility data on hydroxyl sodalite in high ionic strength solutions at elevated temperatures. A validation test comparing model-independent experimental data to model predictions demonstrates that the solubility values produced by the model are in excellent agreement with the experimental data. In addition, the equilibrium constants obtained in this study have a wide range of applications, including synthesis of hydroxyl sodalite, de-silication in the Bayer process for extraction of alumina, and the performance of proposed sodalite waste forms in geological repositories in various lithologies including salt formations. The thermodynamic calculations based on the equilibrium constants obtained in this work indicate that the solubility products in terms of m ΣAl ×m ΣSi for hydroxyl sodalite are very low (e.g., ~10 -13 [mol·kg -1 ] 2 at 100°C) in brines characteristic of salt formations, implying that sodalite waste forms would perform very well in repositories located in salt formations. Finally, the information regarding the solubility behavior of hydroxyl sodalite obtained in this study provides guidance to investigate the performance of other pure end-members of sodalite such as chloride- and iodide-sodalite, which may be of interest for geological repositories in various media.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Graph neural networks for CO 2 solubility predictions in Deep Eutectic Solvents

Deep Eutectic Solvents (DESs) are a promising class of solvents for CO 2 capture. DESs are complex mixtures that can be designed to optimize CO solubility and overall capture process efficiency. However, the vast design landscape of DES mixtures makes experimental investigation prohibitive; as such, there is a need for computational models that can quickly and efficiently navigate the design space and inform data collection efforts. In this work, we propose Graph Neural Network (GNN) models for predicting CO 2 solubility for DESs; the GNN leverages a mixture graph representation that captures the molecular structure of the DES components as well as their intermolecular interactions. Here, we compare the GNN framework against alternative architectures (neural networks, graph convolution networks, and random forests) and data representations (molecular fingerprints, sigma profiles, and graphs). We show that the proposed approach offers superior predictive performance; specifically, we show that solubility can be predicted reliably directly from molecular structure (without the need of using sigma profiles as proposed in previous studies). This result is important, as obtaining sigma profiles requires expensive density functional theory computations. We also explored the ability of GNNs to predict solubility for new DES mixtures and operating conditions. We found that the model extrapolates across temperature reliably. However, we also found deficiencies in the ability of the model to predict solubility for DES mixtures, pressures, and molar ratio not included in the training sets; we show that this is due to an inherent lack of chemical diversity in datasets available in the literature. The proposed computational capabilities can thus help navigate the design space of DES and inform data collection efforts. Our models, data, and benchmarks are shared as Python code implemented in Jupyter notebooks.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Electrochemistry of soluble UO 2 2+ from the direct dissolution of UO 2 CO 3 in acidic ionic liquid containing water

The direct dissolution of UO 2 CO 3 in neat and “wet” ionic liquid (IL) trimethyl-n-butylammonium bis(trifluoromethansulfonyl)imide [Me 3 N n Bu][TFSI] is examined. The ionic liquid serves as both the solvent for the direct dissolution of UO 2 CO 3 (s) and the electrolyte solution for the electrochemical analysis of the soluble uranyl species. The solubility data indicate that displacement of the CO 3 2- occurs slowly due to the low concentration of protons available from residual water in the pristine IL. Enhanced dissolution of UO 2 CO 3 through the formation of carbonic acid H 2 CO 3 is achieved after the addition of acid, bis(trifluoromethanesulfonyl)amide (HTFSI) and water. The soluble uranyl cation can then coordinate with the TFSI anion in place of the displaced CO 3 2- anion following the decomposition of carbonic acid and purging of CO 2 (g) and water from the IL. The solubility of UO 2 CO 3 was examined using liquid scintillation counting of 233 U for the pristine ionic liquid. The “wet” ionic liquid containing HTFSI and soluble UO 2 CO 3 was evaluated using UV/vis spectroscopy before and after dissolution. The electrochemical deposition of uranium species from ionic liquid was evaluated using cyclic voltammetry. The potential mediated deposition of uranium species was achieved and verified using scanning electron microscopy (SEM) and the solid uranium deposits were evaluated using energy dispersive X-ray emission spectroscopy (EDX).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

An Experimental Study of the Solubility of Rare Earth Chloride Salts (La, Nd, Er) in HCl Bearing Water Vapor from 350 – 425 °C

In this work, the solubilities of the rare earth chlorides REECl 3 , where REE = (La, Nd, Er), were measured in HCl bearing water vapor from 350 – 425°C with water partial pressures ranging from 8 – 170 bar. Solubility data were fit to the Pitzer-Pabalan quasi-chemical model in order to extract thermodynamic parameters for the formation of the gaseous REE-chloride-water clusters REECl 3 (H 2 O) n . The data show that the solubility of the REE chlorides are orders of magnitude higher than salts such as NaCl or CuCl at low water fugacities, despite their sublimation energies being substantially higher. This enhanced solubility is likely due to the high enthalpy associated with binding a single water molecule to form the species REECl 3 (H 2 O), with derived enthalpies ranging from –378 to –465 kJ/mol. Addition of further water molecules to form higher order clusters (n > 1) involves enthalpy changes of ~ -20 kJ/mol, and are in effect thermodynamically suppressed over the temperature range 350 – 425°C. Despite the enhanced solubility of small REECl 3 water clusters, simulations of boiling processes demonstrate that the REE show highly conservative behavior, partitioning strongly into the dense aqueous phase. Not surprisingly, the presence of phosphates in the system makes this effect even more pronounced, completely immobilizing the REE. This would reduce transport in both the vapor and aqueous phase to negligible levels. However, we suggest that vapor phase transport of the REE may play a significant role in systems having a relatively low partial pressure of water (below the saturation point), where the relatively high stability of the first hydrated REE chloride clusters (REECl 3 (H 2 O) and REECl 3 (H 2 O) 2 ) will give a preference for gas transport of the REE relative to other elements. This can likely happen in systems involving a gas/melt exchange in fumarolic exhalations, where water vapor discharges at relatively low (close to atmospheric) pressures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

The solubility of ErPO 4 and Er speciation in hydrothermal fluids at varying pH and salinity between 350 and 450 °C

The rare earth elements (REE) are important for the green-energy transition and can be incorporated into the REE phosphates, such as xenotime-(Y), which also hosts heavy REE (Tb– Lu). Xenotime-(Y) is a common accessory mineral in metamorphic rocks and a range of mineral deposits where it controls the mobility of heavy REE, however, the impact of high temperature aqueous fluids on the behavior of heavy REE is largely unknown. Thermodynamic modeling can be utilized as a tool to predict the mobility of REE in hydrothermal aqueous fluids, but must be supported by accurate experimental data. Here, we measured the solubility of endmember synthetic xenotime-structured ErPO4 in NaCl-HCl-NaOH-bearing aqueous solutions at 350 °C and water vapor saturation pressure, at 400 and at 450 °C and 500 bar using batch-type Inconel reactors. Erbium speciation was investigated as a function of pH from 2.8 to 8, where Er chloride species are predominant at acidic conditions (pH <3) and Er hydroxyl complexes are predominant at near- neutral to alkaline conditions (pH >3). At pH 7–9, the measured ErPO 4 solubility (-9.8 to -7.5 log m Er ) is up to 2.5 orders of magnitude lower than thermodynamic predictions (-9.4 to -6.7 log m Er ) using existing thermodynamic databases. At pH 2–3, the predicted ErPO 4 solubility is ~0.5 orders of magnitude higher at 350 °C and ~1 order of magnitude lower at 450 °C compared to experimentally measured Er concentrations. The thermodynamic properties of aqueous Er species were therefore revised in this study. The partial molal Gibbs energy of formation (Δ f G 0 T,P ) for aqueous Er hydroxyl and chloride species are optimized using GEMSFITS and the logarithmic formation constants (logβ n ( Cl,OH) ) were derived at each experimental temperature and pressure. The updated thermodynamic properties for Er hydroxyl species (Er(OH) +2 , Er(OH) 2 + , and Er(OH) 3 0 ) show that their stability shifts to more acidic conditions at and below 400 °C. The Er chloride species (ErCl +2 and ErCl 2 + ) show increased stability compared to Er hydroxyl species at temperatures of 450 °C and 0.01 mol/kg NaCl. The updated thermodynamic properties are implemented into the GEM-Selektor modeling package to investigate the mobility of Er in saline hydrothermal fluids in equilibrium with alkaline rocks. Importantly, the updated properties for Er hydroxyl species result in low Er solubility at rock equilibrated pH conditions due to an expanded hydroxyl predominance zone, but lower aqueous complex stability overall, whereas previous models suggest greater stability for aqueous Er species. Furthermore, ErPO 4 solubility increases with decreasing temperature due to the deprotonation of HCl, which increases the acidity of hydrothermal fluids and the availability of Cl - to complex with the REE. These simulations highlight how fluid-rock reaction and temperature affect the mobility of REE in hydrothermal ore-forming systems.

58 GEOSCIENCES↗
DOE OSTI2025

Decoding the Effect of Anion Identity on the Solubility of N -(2-(2-Methoxyethoxy)ethyl)phenothiazine (MEEPT)

Variations in the solubility of redox-active organic molecules (ROM) of interest for nonaqueous redox flow batteries (RFB), especially as the ROM state-of-charge changes during charge-discharge cycling, present significant molecular design challenges. The situation is further complicated as ROM solubility can be regulated by the choice of electrolyte salt and solvent that together with the ROM comprise the catholyte or anolyte (redox electrolyte) formulation, presenting materials design challenges. The ROM N-(2-(2-methoxyethoxy)ethyl)phenothiazine (MEEPT) is a viscous liquid at room temperature and is miscible in several organic solvents, including acetonitrile and propylene carbonate. The MEEPT radical cation (MEEPT +· ) paired with tetrafluoroborate (BF 4 - ) in acetonitrile presents a 0.5 M solubility, a dramatic decrease when compared to the viscous liquid of neutral MEEPT. Here, in this study, we present a joint experimental, regression modeling, and molecular dynamics (MD) simulations investigation to explore MEEPT-X (where X represents the counteranion) salt solubility variability as a function of concentration and counteranion chemistry in acetonitrile. We find a strong dependence of the salt solubility on the counteranion and relate these findings to explicit intermolecular interactions between MEEPT +· and the counteranion in the electrolyte solution.

Perera, Anton S. [Univ. of Kentucky, Lexington, KY↗
DOE OSTI2015

Sigmoid Correlations for Gas Solubility and Enthalpy Change of Chemical Absorption of CO 2

Knowledge of the relationship between gas solubility and enthalpy change of chemical absorption of CO 2 is very important for exploring energy-efficient absorbents for CO 2 capture. To this end, equations that can directly correlate gas solubility with absorption enthalpy were derived through combining the van’t Hoff equation with the reaction equilibrium thermodynamic model (RETM). In this study, two typical reaction mechanisms for chemical absorption of CO 2 (1:1 and 1:2) were considered for RETM. The variations of gas solubility with enthalpy change were found to be distinctively sigmoid functions, regardless of the investigated temperature and pressure or assumed reaction forms between CO 2 and the absorbent molecule. Theoretically calculated variation curves of gas solubility vs enthalpy change agreed well with experimental results reported in literature. Also, on the basis of the trade-off relationship between gas solubility and enthalpy change, criterions for evaluating energy-efficient chemical absorbents for CO 2 capture were proposed.

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

Aggregation and Solubility of a Model Conjugated Donor–Acceptor Polymer

In conjugated polymers, solution-phase structure and aggregation exert a strong influence on device morphology and performance, making understanding solubility crucial for rational design. Using atomistic molecular dynamics (MD) and free-energy sampling algorithms, we examine the aggregation and solubility of the polymer PTB7, studying how side-chain structure can be modified to control aggregation. We demonstrate that free-energy sampling can be used to effectively screen polymer solubility in a variety of solvents but that solubility parameters derived from MD are not predictive. We then study the aggregation of variants of PTB7 including those with linear (octyl), branched (2-ethylhexyl), and cleaved (methyl) side chains, in a selection of explicit solvents and additives. As a result, energetic analysis demonstrates that while side chains do disrupt polymer backbone stacking, solvent exclusion is a critical factor controlling polymer solubility.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗