Performance of polysulfone membrane for biogas upgrading

Palm oil production process generates abundant waste known as palm oil mill effluent (POME) that can naturally form biogas through the anaerobic digester (AD) process. The use of POME-based biogas as an alternative fuel, despite crucial to control the industry's environmental impact, are still very limited because of the CO2 impurities in it. In this study polysulfone (PSf) membranes were prepared for CO2/CH4 gas separation. Membranes were prepared by phase inversion method with variations of PSf concentration in the casting solution of 18, 20, and 22 wt%. PSf concentration in casting solution was found to closely affect membranes CO2/CH4 separation performances, where both CO2 and CH4 permeability decreases as PSf concentration increases. However, increasing PSf concentration from 18 to 22 wt% was found to improve CO2/CH4 selectivity from 1.65 to 3.47. The separation performance improvement can be attributed to changes in membrane thickness and pore size as polymer concentration in casting solution changes. Gas permeation test result showed CH4 content in purified biogas to be as high as 77% of volume.