Recovery of ionic liquids from methanol by pervaporation with polydimethylsiloxane membrane

Abstract

Pervaporation (PV) is a new membrane technology for the separation of liquid mixtures and has many advantages, such as high efficiency, low energy consumption, simple process and convenient operation. In this work, we investigated the recovery (separation) of ionic liquids (ILs) from methanol by PV with polydimethylsiloxane (PDMS) membrane for the first time. PDMS membrane was prepared using polyvinylidene fluoride (PVDF) membrane with sponge-like holes as base membrane. Five ILs were synthesized, i.e., 1,3-dimethylimidazolium dimethylphosphate ([MMIM][DMP]), 1-ethyl-3-methylimidazolium diethylphosphate ([EMIM][DEP]), 1-butyl-3-methylimidazolium dibutylphosphate ([BMIM][DBP], 1-butyl-3-methylimidazolium cholorate ([BMIM][Cl]), and 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]). The influences of temperature, IL concentration, and IL specifies were investigated. It is observed that ILs do not penetrate through PDMS membrane. The flux increases along with temperature while decreases along with IL concentration in feed. Also, the flux depends on ILs species, and decreases following the order [EMIM][BF4] > [BMIM][DBP] > [BMIM][Cl] > [EMIM][DEP] > [MMIM][DMP]. A stable flux of 1666–1746 g m−2 h−1 was observed in a continuous running of 100 h, showing that PDMS membrane has a good stability for recovery of ILs from methanol. This work shows the PV with PDMS membrane is a good new method for recovering ILs from organic solvents.