Modelling interfacial properties of ionic liquids with ePC-SAFT combined with density gradient theory

Highlights

• Combination of ePC-SAFT with density gradient theory

• Calculation of interfacial properties of pure ILs in broad temperature range

• Quantitative predictions of surface tensions for ILs not used in κ parameter fitting

ABSTRACT

In this work, density gradient theory (DGT) was combined with electrolyte perturbed-chain (ePC)-SAFT to model the interfacial properties of pure imidazolium-based ionic liquids (ILs). The ePC-SAFT pure-component parameters for the IL-ions were taken from literature for the modelling of density and chemical potential of the pure ILs in the bulk phase. The calculated results were used as inputs for modelling surface tension using DGT. The influence parameters for DGT were obtained from the fitting of the experimental surface tensions. Application of anion-specific influence parameters linearised with the molecular weight of the IL-cation allowed to model surface tensions of pure ILs in a broad temperature range within experimental uncertainty. Surface tensions of ILs which have not been used for the fitting of the influence parameter were predicted in quantitative agreement with experimental data. DGT+ePC-SAFT was further used to predict the interfacial density profile of pure ILs.

KEYWORDS:

• Ionic liquid
• ePC-SAFT
• DGT
• surface tension
• density profile

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

G. S. and X. J. acknowledge the financial support from the Swedish research council. X. J. thanks the project of the National Natural Science Foundation of China [grant number 21428601]. X. L. thanks the Key Project of the National Natural Science Foundation of China [grant number 21136004] and National Basic Research Program of China [grant number 2013CB733500]. This work was partially supported by the Foundation of Jiangsu Provincial Engineering Laboratory for Advanced Materials of Salt Chemical Industry [grant number SF201503].