Polysulfone hollow fiber gas separation membranes filled with sub-micron particles

Three different fillers, carbon black (CB), vapor grown carbon fibers (VGCF), and TiO2, were incorporated into polysulfone spinning solutions with the intention of producing highly selective membranes with enhanced mechanical strength. The effect of filler presence on gas permeation characteristics, mechanical strength (bursting pressure), and morphology was investigated and compared to unfilled membranes. As well as studying filler types, the influence of CB filler concentration on membrane performance was also examined. For all filler types (at a concentration of 5%w/w), the pressure-normalized flux of O2, N2, and CH4 was greater in the composite than in the unfilled membranes. The CO2 pressure-normalized flux was only greater in the TiO2 composite membranes. For CB and VGCF, the CO2 pressure-normalized flux was reduced compared with unfilled membranes. Three CB concentrations were investigated (2, 5, and 10%w/w). For O2, N2, and CH4, pressure-normalized flux peaked at 5%w/w CB. CO2 exhibited the opposite trend, showing a minimum pressure-normalized flux at 5%w/w. Considering O2/N2 and CO2/CH4 gas pairs and the various filled membrane categories, only the O2/N2 selectivity of the 2%w/w CB filled membranes was higher than that of the unfilled fibers—all other selectivities were lower. In terms of CB concentration, selectivity was a minimum at the intermediate concentration of 5%w/w. All the filled membrane types exhibited greater mechanical strength (bursting pressure) than unfilled fibers apart from the 5%w/w VGCF composites. The 2%w/w CB composites were the strongest. Electron microscopy showed no visible differences in general morphology between the various filled and unfilled membranes.