Polyether-block-amide thin-film composite hollow fiber membranes for the recovery of butanol from ABE process by pervaporation

This work reports the continuation of previous efforts to recover butanol from the ABE (acetone-butanol-ethanol) fermentation process by pervaporation (PV). A key aspect to improve the efficiency of the technology is the membrane used to perform the selective butanol separation; hence, this study focuses on the implementation of hollow fiber (HF) membrane configuration for the ABE separation by PV as opposed to flat sheet membrane configuration. The HF membrane preparation was done by dip coating, a frequently used process for the production of HF membranes, which involves the deposition of a thin film of a coating solution. Different thicknesses of the active layer were obtained by modifying the polymer content in the coating solution, allowing later to evaluate the influence of the thickness on the separation performance. This study includes a description of the procedure to prepare selective membranes, its characterization and an analysis of the influence of operating conditions on membrane separation performance. SEM and water contact angle were used to characterize the produced membranes. The mass transport phenomena in the pervaporation process were characterized using a resistances-in-series model. The results allow to adopt a criterion to select the most suitable thickness for the membrane active layer, which allows to achieve an adequate separation performance, and reveal the importance in the choice of the membrane support material. Finally, a comparative analysis of the self-made hollow fiber membranes performance in terms of flux, separation factor and PSI with respect to those found in the literature is presented.