Density and Refractive Index of Binary Ionic Liquid Mixtures with Common Cations/Anions, along with ANFIS Modelling

Vakili-Nezhaad, Gholamreza and Mohammadzaheri, Morteza and Farzaneh, Mohammadi and Mohammed, Humaid (2022) Density and Refractive Index of Binary Ionic Liquid Mixtures with Common Cations/Anions, along with ANFIS Modelling. Liquids, 2 (4). ISSN 2673-8015

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Ionic liquids have many interesting properties, as they share the properties of molten salts as well as organic liquids, such as low volatility, thermal stability, electrical conductivity, non-flammability and much more. Ionic liquids are known to be good solvents for many polar and nonpolar solutes. Combined with their special properties, ionic liquids are good replacements for the conventional toxic and volatile organic solvents. Each ionic liquid has different properties than others. In order to alter, tune and enhance the properties of ionic liquids, sometimes it is necessary to mix different ionic liquids to achieve the desired properties arises. However, using mixtures of ionic liquids in chemical processes requires reliable estimations of the mixtures physical properties such as refractive index and density. The ionic liquids used in this work are 1-butyl-3-methylimidazolium thiocyanate ([BMIM][SCN]), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]), 1-hexyl-3-methylimidazolium tetrafluoroborate ([HMIM][BF4]), and 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM][PF6]). These ionic liquids were supplied by Io-li-tec, and used as received. However, new measurements for the density and refractive index were taken for the pure ionic liquids to be used as reference. In the present work, densities and refractive indices of four different binary mixtures of ionic liquids with common cations and/or anions have been measured at various compositions and room conditions. The accuracy of different empirical mixing rules for calculation of the mixtures refractive indices was also studied. It was found that the overall absolute average percentage deviation from ideal solution in calculation of molar volume of the examined binary mixtures is 0.78%. Furthermore, all of the examined mixing rules for calculation of refractive indices of the mixtures were found to be accurate. However, the most accurate empirical formula was found to be Heller's relation with an average percentage error of 0.24%. Furthermore, an artificial intelligence model, an adaptive neuro-fuzzy inference system (ANFIS), was developed to predict density and refractive index of different mixtures studied in this work as well as the published literature data. The predictions of the developed model were analyzed by various methods including both statistical and graphical approaches. The obtained results show that the developed model accurately predicts the density and refractive index with an overall R2, RMSE and AARD% values of 0.968, 7.274, 0.368% and 0.948, 7.32E-03 and 0.319%, respectively for external validation dataset. Finally, a variance-based global sensitivity analysis was formed using extended Fourier amplitude sensitivity test (EFAST). Our modeling showed that the ANFIS model outperforms the best available empirical models in the literature for predicting refractive index of the different mixtures of ionic liquids.

Item Type: Article
Identification Number:
27 November 2022Accepted
5 December 2022Published Online
Uncontrolled Keywords: refractive index, density, ionic liquids, mixtures, ANFIS
Subjects: CAH00 - multidisciplinary > CAH00-00 - multidisciplinary > CAH00-00-00 - multidisciplinary
CAH10 - engineering and technology > CAH10-01 - engineering > CAH10-01-09 - chemical, process and energy engineering
CAH11 - computing > CAH11-01 - computing > CAH11-01-05 - artificial intelligence
Divisions: Faculty of Computing, Engineering and the Built Environment > School of Engineering and the Built Environment
Depositing User: Morteza Mohammadzaheri
Date Deposited: 05 Dec 2022 16:10
Last Modified: 08 Dec 2022 11:37

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