Fabrication of Polymeric Ultrafiltration Membranes Using Ionic Liquids as Green Solvents

Abstract

This study has explored, for the first time, the fundamentals and engineering of using ionic liquids as a new generation of solvents for the fabrication of polymeric ultrafiltration membranes. This study has investigated the molecular interactions between imidazolium-based ionic liquids and polymeric materials including cellulose acetate and polybenzimidazole (PBI). The studied ionic liquids were capable to interact intensely with CA or PBI molecules mainly due to the electrostatic nature of ionic liquids, which have been verified by molecular simulations and rheological studies. By adjusting membrane fabrication conditions and investigating membrane formation mechanisms, CA flat sheet membranes, hollow fiber membranes as well as PBI flat sheet membranes have been prepared using ionic liquids as the solvents for the first time. The resultant PBI ultrafiltration membranes achieved a high separation factor of 94.55 for a binary protein mixture. Newly developed PBI/ co-polyimide blend membranes exhibited 50% increase of pure water permeability with an open cell structure and a reduced thickness.