Correlating Excess\nVolumes for Binary Mixtures of\nGreen Solvents with the Help of Density Functional Theory

The development of green solvents is vital to decrease\nthe environmental\nimpact of separation processes by replacing their more hazardous equivalents,\nwhich often lack biodegradability, nontoxicity, and biocompatibility.\nNevertheless, the application of green solvents in industry has been\nlimited by the insufficiency of thermophysical data on their mixtures,\nwhich is due to low technological maturity and high cost of experimentation.\nSo, there is a mounting interest in using computational chemistry\nas a predictive methodology. In this work, the liquid densities <i>(ρ)</i> of the binary mixtures of ethyl lactate or cholinium <i>iso</i>-leucinate with water or ethanol were determined at 288.15,\n293.15, 298.15, 303.15, or 308.15 K and 0.1 MPa. Then, the calculated\nexcess volumes (<i>V</i><sup>E</sup>) were correlated with\nmolar composition using three different methodologies: third-degree\npolynomials; Redlich–Kister expansions; and a novel approach\nbased on computational chemistry (density functional theory). The\nstandard deviation (σ) of these approaches to experimental data\nshowed that the novel methodology, which relied on calculating molar\nvolumes by combining B3LYP/6-311++G(d) with the integral equation\nformalism polarizable continuum model, obtained a better description\nof the binaries (1.18 × 10<sup>–8</sup> < σ/m<sup>3</sup>·mol<sup>–1</sup> < 6.56 × 10<sup>–8</sup>) than third-degree polynomials (1.25 × 10<sup>–7</sup>< σ/m<sup>3</sup>·mol<sup>–1</sup> < 15.0×\n10<sup>–7</sup>) and Redlich–Kister expansions (3.40\n× 10<sup>–8</sup> < σ/m<sup>3</sup>·mol<sup>–1</sup> < 8.74 × 10<sup>–8</sup>). Moreover,\nthis novel methodology was considered to decrease the number of adjustable\nparameters while, at the same time, providing a more concrete physical\nmeaning to the parameters and enhanced accuracy and predictivity.