Modeling of Gas Solubility in Aqueous Electrolyte Solutions with the eSAFT-VR Mie Equation of State

Abstract

In this work, the eSAFT-VR Mie EoS is applied to watermethanesalt and watercarbon dioxidesalt mixtures. Initially, the EoS parameters for non-electrolyte systems are fitted and temperature dependent waterion interaction parameters are introduced to improve the behavior of the model at high temperatures. Furthermore, a database of experimental methane and carbon dioxide solubility in single-salt aqueous solutions was compiled and is given in SI units as Supporting Information. Four different parameterization schemes regarding gasion dispersion energy have been pursued in this work, namely: (a) setting the gasion dispersion energy parameter to zero, (b) using the SAFT-VR Mie combining rules without any binary interaction parameters, (c) using the predictive Hudson -McCoubrey combining rules and last but not least (d) fitting to experimental solubility of gases in aqueous solutions of single salts. The fitting approach yields an average deviation from experimental data of about 10%, compared to more than 25% for the other approaches. However, despite the great overall deviations of the predictive methods, there are cases where they yield excellent results, such as methane solubility in aqueous NaCl solutions. The salting-out behavior predicted with the fitted parameters is excellent at room temperature but deviate from experimental data at higher temperatures. Finally, the model is applied to gas solubility in mixed salt solutions, without further adjustable parameters and the predictions are in excellent agreement with experiments. Overall, eSAFT-VR Mie shows great potential for gas solubility calculations under salinity.

A New Force Field for OH– for Computing Thermodynamic and Transport Properties of H2 and O2 in Aqueous NaOH and KOH Solutions

“…Modeling electrolyte systems is a challenging endeavor because of the strong long-range ionic interactions, which make the solutions highly nonideal. ,− Electrolyte solutions are commonly modeled using semiempirical equations of state and molecular based simulations. ,− Semiempirical equations provide a rapid and convenient method for the prediction of thermophysical properties . The quality of these equations depends on the availability of accurate experimental and simulation data. − For aqueous alkaline solutions, experimental data for self-diffusivities and solubilities of H 2 and O 2 at high concentrations (above 4 mol/kg), temperatures (323–373 K), and pressures (above 50 bar) is lacking, especially in the case of aqueous NaOH solutions. , These temperatures (ca. 353 K) and concentrations (4–12 mol/kg electrolyte solution) are especially relevant for alkaline electrolyzers. ,,− Molecular simulations (i.e., molecular dynamics (MD) and Monte Carlo (MC)) can be used as a complementary approach to experiments to provide insight at conditions for which experimental data are limited and difficult to obtain due to high temperatures, pressures, and the corrosiveness of the solution (in case of strong alkaline solutions).…”

“…Modeling electrolyte systems is a challenging endeavor because of the strong long-range ionic interactions, which make the solutions highly nonideal. ,− Electrolyte solutions are commonly modeled using semiempirical equations of state and molecular based simulations. ,− Semiempirical equations provide a rapid and convenient method for the prediction of thermophysical properties . The quality of these equations depends on the availability of accurate experimental and simulation data. − For aqueous alkaline solutions, experimental data for self-diffusivities and solubilities of H 2 and O 2 at high concentrations (above 4 mol/kg), temperatures (323–373 K), and pressures (above 50 bar) is lacking, especially in the case of aqueous NaOH solutions. , These temperatures (ca.…”

“… 15 The quality of these equations depends on the availability of accurate experimental and simulation data. 18 − 22 For aqueous alkaline solutions, experimental data for self-diffusivities and solubilities of H 2 and O 2 at high concentrations (above 4 mol/kg), temperatures (323–373 K), and pressures (above 50 bar) is lacking, especially in the case of aqueous NaOH solutions. 14 , 27 These temperatures (ca.…”

Estimating CO2 Solubility in Aqueous Na+–K+–Mg2+–Ca2+–Cl––SO42– Solutions with Electrolyte NRTL–PC-SAFT Model

“…The model also requires regressing a large matrix (14 × 6) of parameters for CO 2 + H 2 O binary system which might be computationally expensive. Recently, Novak et al developed an EoS called electrolyte SAFT for variable range (eSAFT-VR) Mie to estimate the solubility of CO 2 in water, single salts, and mixed-salt solutions. They initially used the SAFT-VR Mie (a generalized Lennard-Jones potential form) framework to obtain the temperature-dependent interaction parameters for CO 2 and H 2 O to represent CO 2 + H 2 O binary system and then extended their model by including the Debye–Hückel and Born terms to account for the presence of salts.…”

“…A majority of the aforementioned models ,,,,,,,− use the Pitzer equation and its variants to estimate CO 2 solubility in aqueous salt solutions. A limitation of the Pitzer equation is that the model requires a large number of temperature dependent binary and ternary ion interaction parameters, and the extension to predict CO 2 solubility in mixed-salt solutions at different operating conditions becomes cumbersome. , Additionally, only a few models ,,,,,,,,, estimate the solubility of H 2 O in the CO 2 -rich phase, whereas most of the models only focus on estimating CO 2 solubility in the aqueous phase. Solubility predictions in both CO 2 -rich phase and H 2 O-rich phase are critical for accurately representing the VLE behavior.…”