Vapor pressures were measured for six binary systems containing water

ethanol

or methanol with one of the two ionic liquids (ILs) at different component concentrations and temperatures using a quasi-static ebulliometer

with the ILs mono-ethanolammonium formate ([HMEA][HCOO]) and di-ethanolammonium formate ([HDEA][HCOO]). The vapor pressures of the IL-containing binary systems are well correlated using the NRTL model with an overall average absolute relative deviation (AARD) of 0.0062. The effect of ILs on the vapor pressure depression of solvents at 0.050 mole fraction of IL is that [HDEA][HCOO] [HMEA][HCOO]

and the vapor pressure lowering degree follows the order of water methanol ethanol. Further

the activity coefficients of three solvents (viz. water

ethanol

and methanol) for the binary systems {solvent (1) + IL (2)} predicted based on the fitted NRTL parameters at T=333.15 K indicate that the two ILs generate a negative deviation from Raoult's law for water and methanol and a positive deviation for ethanol to a varying degree

change the relative volatility of a solvent. [HMEA][HCOO] may be a promising entrainer to efficiently separate ethanol aqueous solutions by special rectification.