Supression of plasticization on assymetric hollow fiber polysulfone membrane using constant heating and progressive heating techniques

Abstract

This study investigates the effect of heating on suppression of plasticization effect upon asymmetric hollow fiber polysulfone membranes for carbon dioxide/methane separation. The membranes were fabricated using polysulfone (Udel P1700) and heat treated before tested on pure methane and carbon dioxide gases to study their gas separation characteristics. Constant temperature heating and progressive temperature heating were applied to the membranes. The produced membranes were then characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and fiber density calculation. Membranes treated with constant temperature heating exhibits lower pressure-normalize flux for both carbon dioxide and methane while their selectivity increased compared to untreated membranes. This was probably due to densification of membrane skin layer during heating process. Denser skin layer increases the resistance in the membrane which resulted in decreased of pressure-normalize flux. A higher density of membrane skin layer was achieved by progressive temperature heat treatment. This further increased the resistance in the membrane resulted in a lower value of pressure normalized-flux which surpasses the intrinsic value. The application of different feed pressure caused an almost linear value of CO2 and CH4 pressure-normalize flux were observed. This indicated that plasticization is successfully suppressed by heat treatment. At progressive heating to 90ºC, a modest pressure-normalized flux value of 0.16 GPU and 4.34 GPU were achieved for CH4 and CO2, respectively. It is also observed that the CO2/CH4 selectivity increases with increment of temperature for both type of heating. However, progressive heating to 90ºC shows a promising selectivity result of 27.06. From the results provided in this study, it can be concluded that plasticization of polysulfone hollow fiber membrane is successfully suppressed by heat treatment process.