Improving Gas Separation Properties of PEI Membrane by Applying Mixed Solvent in Membrane- Forming System

It is more than a decade that polymeric membranes are used as gas separators. Membrane selectivity and permeability are two parameters that can identify its gas separation performance. Ithas been demonstrated that membrane material and morphology and also the components of a gas mixture playimportant roles in gas separation performance [1]. PEI membrane is a remarkable issue in gas separation and can fabricate in an immersion precipitation process in which it leads to an asymmetric structure. This structure is composed of a dense skin layer and a porous sub-layer. Skin isresponsible for separation and it is expected that the solutiondiffusion mechanism is predominant for transport [2]. The transport properties of membrane are controlled by somefactors, one of them is mix solvent in casting solution. Since this active layer contains some surface defects, gas moleculespermeate through it via Knudsen mechanism. So, gas separation performance improves by coating polydimethylesiloxane (PDMS) layer with high permeability but low selectivity properties on the surface of membranes [3].