Ba_0.5Sr_0.5Co_0.8Fe_0.2O _3-δ ceramic hollow-fiber membranes for oxygen permeation

Self-supported asymmetric hollow-fiber membranes of mixed oxygen-ionic and electronic conducting perovskite Ba_0.5Sr_0.5Co _0.8Fe_0.2O_3-δ (BSCF) were prepared by a combined phase-inversion and sintering technique. The starting inorganic powder was synthesized by combined EDTA-citrate completing process followed by thermal treatment at 600°C. The powder was dispersed in a polymer solution and then extruded into hollow-fiber precursors through a spinneret. The fiber precursors were sintered at elevated temperatures to form gastight membranes, which were characterized by SEM and gas permeation tests. Performance of the hollow fibers in air separation was both experimentally and theoretically studied at various conditions. The results reveal that the oxygen permeation process was controlled by the slow oxygen surface exchange kinetics under the investigated conditions. The porous inner surface of the prepared perovskite hollow-fiber membranes considerably favored the oxygen permeation. The maximum oxygen flux measured was 0.031 molm^-2s^-1 at 950°C with the sweep gas flow rate of 0.522 molm^-2s^-1. To improve the oxygen flux of BSCF perovskite membranes, future work should be focused on surface modification rather than reduction of the membrane thickness.