Sorption property, excess enthalpy, and solvatochromic parameters of choline lactate

Abstract

Sorption properties, including isotherm shape, adsorption energy, maximum uptake, and cyclic hydrothermal stability, have a significant influence on the optimization of absorbents for diverse desiccant air conditioning systems. The sorption behavior of the water/choline lactate ([ch][lac]) pair was examined using a dynamic vapor sorption (DVS) analyzer. Data analysis identified type-III isotherms. The Dubinin-Astakhov (D-A) formulation, defined by a temperature-independent Polani potential, was successfully applied to the sorption equilibrium curve. The Kamlet-Taft polarity parameters were tested using solvatochromic probes with a UV/Vis spectrophotometer. Multivariate regression analysis was performed to correlate the water affinity coefficient of the D-A model with the Kamlet-Taft polarity parameters using linear solvation energy relationships (ISERs). The solvatochromic parameter of dipolarity/palarizability (π*) had a positive contribution to the water affinity coefficient of ionic liquid (IL) desiccants, and the general trend of influence was hydrogenbondacidity(α)>π*>hydrogenbondbasicity(β). Excess enthalpies were correlated well with solvatochromic parameters. The differential enthalpies and entropies, first virial coefficient (A0), and isosteric enthalpies of sorption at zero surface coverage were also discussed. The enthalpy of activation at zero surface coverage was deduced from sorption kinetics. The hydrothermal cyclic stabilities and ambient regenerabilities were determined by cycle stress tests.