Selective Separation of Toluene/n-Heptane by Supported Ionic Liquid Membranes with [Bmim][BF4]

Abstract

Room-temperature ionic liquids serve as alternative solvents for volatile organic compounds in liquid-liquid extraction and liquid membrane separation. 1-Butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) was applied for extraction and supported ionic liquid membranes (SILMs) to separate toluene and n-heptane. A high separation factor of toluene was achieved due to the strong interaction between ionic liquid cations and toluene. The mass transfer performance of the SILM process was enhanced by higher operating temperature. With the increase of initial toluene concentration in the feed phase, the mass transfer flux and removal efficiency of the SILM process were improved, while the separation factor decreased. The mass transfer flux was growing with the increase of flow rate at both sides. The SILM process was stable over a long time period due to the high viscosity and low volatility of [Bmim][BF4].