Effect of cosolvent on the solubility of glucose in ionic liquids: Experimental and molecular dynamics simulations

Abstract

The present study attempts to measure the solubility of glucose in three neat ionic liquids (ILs), namely 1-ethyl-3-methylimidazolium methylsulfonate [Emim][MeSO3], 1-ethyl-3-methylimidazolium ethyl sulfate [Emim][EtSO4], 1-ethyl-3-methylimidazolium thiocyanate [Emim][SCN] and IL/cosolvent mixtures as a function of temperature. The IL [Emim][MeSO3] has shown higher solubility of glucose than other ILs. The experimental glucose solubility data was further correlated with Apelblat empirical equation along with regression using a local thermodynamic model such as NRTL (non-random two-liquid). The thermodynamic functions of dissolution, such as enthalpyΔdissol∘H, Gibbs energy Δdissol∘G and entropy Δdissol∘S were also determined using the modified van't Hoff equation. The dissolution functions for all the systems studied were positive, indicating that the process is endothermic, non-spontaneous, and entropically viable. Dimethyl sulfoxide (DMSO) was added as a cosolvent to enhance the solubility of glucose in ILs by reducing viscosity, which leads to a higher mass transfer rate of solute in solvent even at low temperatures. Furthermore, we performed molecular dynamics (MD) simulations to understand the microscopic interactions of glucose-IL and glucose-IL/DMSO systems. From the MD simulations, it was observed that anions of IL dominate the solvation of glucose, whereas the cation plays a secondary role. The addition of DMSO to ILs, weakens the stronger interactions between anion and cation of IL, thereby enhancing the solvation of glucose by increasing the interaction energies and contact probabilities between glucose and anion of ILs.