Pervaporation removal of water from ionic liquid solutions using Nafion membranes

We report a pervaporation process to remove water from a solution containing ionic liquid (IL) + solvent + water. Specifically, Nafion-based membranes were employed for the separation, and tributylmethylammonium dimethylphosphate and N-methyl-2-pyrrolidone (NMP) were the IL and solvent, respectively. Membrane swelling in contact with the IL–NMP–H₂O solution was accommodated by judicious use of gaskets and membrane supports. The pervaporation fluxes of water and NMP increased with temperature and flow rate of the permeate sweep gas. Among the membranes examined, a commercially available Nafion membrane (XL, Ion Power) provided the highest water (10 mg h⁻¹ cm⁻²) and NMP (182 mg h⁻¹ cm⁻²) fluxes. The results show that pervaporation separation is a technologically feasible method to decrease the water content of an IL–NMP–H₂O solution from 1 to 0.5 wt%.