Fabrication and use of hollow fiber thin film composite membranes for ethanol dehydration

In this study, the development of thin film composite (TFC) pervaporation hollow fiber membranes for biofuel dehydration at high fluxes is presented. The novel membranes consist of a thin selective polyamide layer formed by interfacial polymerization onto a porous polyethersulfone (PES) hollow fiber support that is free of macrovoids. This membrane support was fabricated using the dual-layer co-extrusion technology to design and effectively control the phase inversion during the membrane formation. The macrovoid-free and highly porous morphology of the membrane support is desirable. Not only does it provide excellent membrane strength, but also minimize the mass transfer resistance encountered during the pervaporation process, thus enhancing the total flux. The effects of key fabrication parameters such as drying methods of hollow fiber supports, interfacial polymerization conditions including heat treatment, different alcohols and water as cleaning solvents on membrane formation, membrane morphology and pervaporation performance of the resultant TFC membranes are systematically investigated and elucidated. The surface modification of the TFC membranes with polydopamine or silicone rubber coatings is proposed to simply and effectively enhance the membrane selectivity. The polydopamine-coated and silicone rubber-coated TFC membranes exhibit water separation factors of up to 51 and 60, with substantial high fluxes of 6.6 and 7.5 kg m−2 h−1, respectively. The newly developed TFC hollow fiber membranes possess reasonably good selectivity/separation factors and superior permeation fluxes in comparison with most polymeric membranes that have been reported in the open literature.