Zhai Z, Paap U, Gezmis A, Maier F, Steinrück HP, Koller TM (2023)
Publication Language: English
Publication Type: Journal article, Original article
Publication year: 2023
Book Volume: 386
Article Number: 122388
DOI: 10.1016/j.molliq.2023.122388
In the present study, we investigated the surface tension and viscosity of binary ionic liquid (IL) mixtures at or close to saturation conditions from high vacuum conditions up to elevated pressures. We studied four different mixtures of 1,3-bis(2-(2-methoxyethoxy)ethyl)imida-zolium iodide ([(mPEG2)2Im]I) and 1-methyl-3-octylimidazolium hexafluorophosphate ([C8C1Im][PF6]) with [C8C1Im][PF6] mole contents between (4.6 and 49.8) mol%. Argon (Ar) gas of relatively low solubility was used to vary the applied pressure between (0.1 and 10) MPa. For temperatures from (303 to 363) K, the surface tension obtained by the pendant-drop (PD) method was used to determine the saturated liquid viscosity from surface light scattering (SLS). These studies are complemented by additional PD measurements under ultraclean high vacuum (HV) conditions in a second setup. At about 0.1 MPa, the surface tension and viscosity of the IL mixtures show negative deviations from a linear mixing rule based on the molar bulk composition, which is more pronounced at lower temperatures. The surface tension values at 0.1 MPa and under HV agree with each other and lie closer to the values of [C8C1Im][PF6] that has a distinctly lower surface tension than [(mPEG2)2Im]I and is surface-active. For the equimolar IL mixture at 303 K, an increase in the pressure up to 10 MPa has a negligible influence on the viscosity, while it causes a distinct reduction in the surface tension compared to the value at 0.1 MPa. The pressure-dependent relative change for the viscosity of the ternary mixtures of the two ILs and Ar corresponds well to the mean values of the positive and negative relative changes observed for the two binary [(mPEG2)2Im]I-Ar and [C8C1Im][PF6]-Ar subsystems, respectively. For the surface tension, the absolute changes at a given pressure are very similar regardless of the IL bulk composition, suggesting a similar weak Ar enrichment at the gas–liquid interface.
APA:
Zhai, Z., Paap, U., Gezmis, A., Maier, F., Steinrück, H.-P., & Koller, T.M. (2023). Surface tension and viscosity of binary ionic liquid mixtures from high vacuum up to pressures of 10 MPa. Journal of Molecular Liquids, 386. https://doi.org/10.1016/j.molliq.2023.122388
MLA:
Zhai, Ziwen, et al. "Surface tension and viscosity of binary ionic liquid mixtures from high vacuum up to pressures of 10 MPa." Journal of Molecular Liquids 386 (2023).
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