Dehumidification of air using liquid membranes with ionic liquids

Abstract This paper presents application of the hygroscopic ionic liquids, such as 1-ethyl-3-methylimidazolium ethylsulfate, 1-ethyl-3-methylimidazolium dicyanamide and 1-ethyl-3-methylimidazolium tetrafluoroborate, for the membrane-based air dehumidification. Liquid membranes, supported by the hydrophobic porous membrane, were prepared and their dehumidification efficiency was evaluated in terms of the water recovery rate and water vapor permeability. The performance of supported liquid membranes, composed of ionic liquid, was higher when compared to that, containing triethylene glycol. Ionic liquids showed recovery of water from 80%RH humid air as high as 10 g/h. The permeabilities of water vapor through the ionic liquids were 26,000–46,000 Barrer and the separation factor to the air was over 1000. These measured permeabilities were compared to that predicted by the solution diffusion mechanism, which was supported by the adsorption, diffusivity and viscosity measurements of the liquids. It was demonstrated that solution–diffusion mechanism well describes transport of air through the ionic liquid membrane and with further considerations can be applied for the description of water vapor transport in ILs.