Optimization of formation process in development of high performance of asymmetric membranes

Abstract

Selectivity and permeability of asymmetric membrane characterize its performance for gas separation process. Unfortunately, there is usually a trade-off between permeability and selectivity thus representing one of the major obstacles to commercial application and production of membranes. Hence serious compromises are required to achieve a defect-free skin layer with minimum thickness in order to avoid dramatic loss in the overall membrane selectivity by maintaining sufficient permeability. Structure and property of asymmetric membrane are intimately tied to its formation mechanism, where slight changes either in the solution recipes or processing parameters can greatly influence the resultant membrane. Specifically, preparation of high performance asymmetric membranes with defect-free and ultrathin skin layers has been performed through the manipulation of two fabrication variables, including solvent ratio and forced-convective evaporation time. Therefore investigation of their effects was conducted by using factorial design, in which the main effects and the interaction effects of variables on membrane structure and performance were analyzed. Indeed the interdependencies of these variables play a critical role in the production of defect free and ultra-thin skinned asymmetric membranes. Based on the analysis of results, optimal processing conditions can be developed to produce high performance asymmetric membranes without the necessity of post-treatments.