[en] Hydrogen bonding interaction between alcohols and water molecules is an important characteristic in the aqueous solutions of alcohols. In this paper, a series of molecular dynamics simulations have been performed to investigate the aqueous solutions of low molecular weight alcohols (methanol, ethylene glycol and glycerol) at the concentrations covering a broad range from 1 to 90 mol %. The work focuses on studying the effect of the alcohols molecules on the hydrogen bonding of water molecules in binary mixtures. By analyzing the hydrogen bonding ability of the hydroxyl (-OH) groups for the three alcohols, it is found that the hydroxyl group of methanol prefers to form more hydrogen bonds than that of ethylene glycol and glycerol due to the intra-and intermolecular effects. It is also shown that concentration has significant effect on the ability of alcohol molecule to hydrogen bond water molecules. Understanding the hydrogen bonding characteristics of the aqueous solutions is helpful to reveal the cryoprotective mechanisms of methanol, ethylene glycol and glycerol in aqueous solutions

[en] Highlights: • Water vapor absorption by LiBr and LiBr + NaCOOH was studied by molecular modeling. • Ionic clustering and hydrogen-bonding in LiBr + NaCOOH + H_2O were analyzed. • A higher LiBr concentration increased the vapor absorption rate. • Strong interactions between Li"+ and COOH"− were found. • Higher absorption capacity may be due to Li"+–COOH"− clustering. - Abstract: Aqueous lithium bromide (LiBr) solutions are commonly-employed as liquid desiccants, largely due to their low water vapor pressure at concentrations suitable for applications such as absorption refrigeration. However, LiBr-based desiccants have drawbacks such as corrosivity, crystallization at high concentrations, and high energy inputs to regenerate the absorbent. It was recently shown that adding formate salts (e.g., NaCOOH) into the LiBr + H_2O mixture could mitigate disadvantages while maintaining most advantages, but these experimental findings were unable to elucidate the driving forces at the molecular level. Detailed knowledge of the molecular interactions that underpin absorption phenomenon in both traditional and newly developed ternary working fluids (e.g., LiBr + NaCOOH + H_2O) is still incomplete. The present molecular modeling study of water vapor absorption by LiBr and LiBr + NaCOOH investigated the water vapor absorption kinetics, enabling the analysis of ionic clustering and hydrogen-bonding characteristics. Molecular simulations of LiBr + H_2O compositions demonstrated that increasing the LiBr concentration enhances the absorption rate while decreasing the liquid–vapor interfacial thickness of the LiBr + H_2O layer. The most interesting finding was the strong interaction between Li"+ and COOH"− which may enable the ternary mixture to accommodate more water molecules as a result of Li"+–COOH"− clustering compared to compositions containing only LiBr and H_2O. Despite an increase in water vapor absorption capacity it was found that adding NaCOOH decreased the water vapor absorption rate. Elucidating the molecular origin that affects the performance of liquid desiccants upon addition of formate salts is a first step toward the rational design of new working fluids for liquid desiccant-related applications.