SIEPM research group made important progress in the field of the recovery of water-soluble ionic liquids

Ionic liquids (ILs) show a wide range of applications as “green” solvents in the new era and the recovery of water-soluble ILs has become an urgent issue. Herein, for the first time, osmotic distillation is applied to concentrate and recover water-soluble ILs with a series of hydrophobic membranes. Poly(vinylidene fluoride) membrane with vertically oriented pores and stainless steel mesh were hydrophobically modified and then compared with commercial membranes to demonstrate the influence of different pore structures on the osmotic distillation concentration process. With the vapor pressure difference between two sides of the membrane being the driving force, the dilute aqueous solutions of ILs can be concentrated to about 84 wt% after 24 h with a water flux of 7.8 kg m⁻² h⁻¹. It is also able to achieve ultra-high rejections to ILs and MgCl₂ (>99.99%) by this osmotic distillation process. Although there exists a limitation for dewatering the ILs solutions with very high concentrations and thus the final ILs purity cannot reach 100%, this method is promising for practical applications benefiting from its high rejection to ions, easy operability at ambient temperature and remarkable universality in terms of hydrophobic membranes used.

DOI：10.1016/j.memsci.2020.118222