This study outlines the methodology to model hydrophobic deep eutectic solvent (HDES) interactions to obtain computational results that accurately represent experimental results of furfural removal from water. Computational prediction with high accuracy of HDES behavior could elucidate hydrogen bond interaction in HDES. COSMOtherm modeling and experimental evaluation demonstrated that both decanoic and dodecanoic acid-based HDES can remove furfural from water even at very low concentrations of 0.1 mol %. The modeling methodology considered salts as independent cations, which were paired with the hydrogen bond donor (HBD) species. These resulted in computational predictions of liquid-liquid equilibrium (LLE) between tetra n-alkyl ammonium bromide salt-based HDES with >95% accuracy of experimental results. The COSMOtherm modeling methodology strengthens the understanding of HDES by considering intermolecular forces that affect electron density (σ) of the HDES components to determine the LLE of the HDES-aqueous system. This results in a deep eutectic phase that has a positive sigma potential (potentials, μ(σ), up to 0.1 kcal/mol Å2) at charge densities associated with hydrogen bonding (±0.0084 e/Å2). Though n-alkyl ammonium salts ranging from tetramethyl- to tetraoctylammonium bromide were considered in the computational model, only pentyl- and longer alkyl chains displayed hydrophobic behavior with less than 1% salt loss to the aqueous phase. However, there was still significant water uptake in the eutectic phase (final phase composition containing greater than 60 mol and 12% by mass) for the hydrophobic DES.
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