Mathematical Representation of Viscosity of Ionic Liquid + Molecular Solvent Mixtures at Various Temperatures Using the Jouyban-Acree Model Abolghasem Jouyban, †, * Jafar Soleymani, ‡ Farshad Jafari, § Mehry Khoubnasabjafari, ⊥ and William E. Acree ¶ † Drug Applied Research Center and Faculty of Pharmacy, ‡ Liver and Gastrointestinal Diseases Research Center, § Biotechnology Research Center, and ⊥ Tuberculosis and Lung Disease Research Center, Tabriz University of Medical Sciences, Tabriz 51664, Iran ¶ Department of Chemistry, University of North Texas, Denton, Texas 76203-5017, United States ABSTRACT: The viscosity of room temperature ionic liquid + molecular solvents is correlated using the Jouyban-Acree model, and the accuracy of the model is evaluated using average relative deviations (ARD) of the calculated and experimental values. The overall ARD of 6.9 % was obtained for the proposed model where the overall ARD for a similar model from the literature was 22.4 %. The mean difference between ARDs of the models was statistically significant. Combined forms of the Jouyban-Acree model and the Abraham parameters were used for predicting the viscosity of the mixtures at various temperatures. The overall ARD for the investigated mixtures was 15.0 % when the experimental viscosity of the pure solvents was included. The ARD of the in silico version of the model was 20.7 %. ■ INTRODUCTION Room temperature ionic liquids (RTILs) are a new class of solvents attracting considerable attention in the pharmaceutical/ chemical industries. RTILs are used in manufacturing nano- materials, high temperature lubricants, excipients for new drug delivery systems, novel stationary phases for gas chromato- graphic systems, and extraction solvents for separation of analytes. Very low vapor pressure, multiple solvation inter- actions with organic and inorganic compounds, very good chemical and thermal stability, high ionic conductivity, and wide melting point temperature ranges are the main advantages of RTILs over common molecular solvents. In addition to the applications of RTILs, their mixtures with molecular solvents are used in the industry providing wider physicochemical properties. Viscosity data of the mixtures are required in some related computations and a number of attempts have been made to collect the experimental values of the viscosity and density of these mixtures. 1-23 Despite these experimental efforts, a number of mathematical models were proposed to compute the properties. The aims of this work are to propose a mathematical model to fit the viscosity data of RTILs + solvent mixtures at various temperatures and also provide global versions of the model to predict the viscosity data. ■ COMPUTATIONAL METHODS Larriba et al. 10 used Bringham mixing rule to estimate the viscosity of binary mixtures containing two ionic liquids. The equation is a reciprocal viscosity prediction as η η η = + x x 1 ( ) ( ) ( ) T T T mix 1 1 2 2 (1) where (η mix ) T is the viscosity of the binary mixture at a given temperature (T), (η 1 ) T and (η 2 ) T denote the viscosity of RTIL and molecular solvent, x 1 and x 2 are mole fractions of RTIL and molecular solvent, respectively. One could probably generalize the equation to include other mixture compositions, such as volume fractions, mass fractions, etc. The equation is a strictly empirical equation. It is an outright prediction of viscosity in that there are no curve-fit parameters. All that one needs is the viscosity of the two pure liquids at each temperature studied. Domanska and co-workers 15 described the temperature dependence of viscosity with the Vogel-Fulcher-Tamman (VFT) equation η = − ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ AT B T T exp 0.5 o (2) and Wang et al. 1 used a slightly different variation η η = − ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ B T T exp o o (3) where A, T o , B, and η o , are curve-fitting parameters depending on which temperature dependence was used. In each study, Received: September 26, 2012 Accepted: April 23, 2013 Published: May 6, 2013 Article pubs.acs.org/jced © 2013 American Chemical Society 1523 dx.doi.org/10.1021/je301057g | J. Chem. Eng. Data 2013, 58, 1523-1528