Microstructure modulation of α-Al₂O₃ hollow fiber membranes with four-channel geometric configuration

α-Al₂O₃ four-channel hollow fiber (4CHF) membrane owns high permeability as well as great mechanical strength. In this work, three typical microstructures of 4CHF membranes with sponge-like layer located in centric (S1), inner (S2) and outer (S3) regions were demonstrated by changing polyethersulfone content of spinning suspension, ethanol contents of internal and external coagulants, respectively. The 4CHF-S1 membrane could be prepared by using water as both internal and external coagulants. The central sponge-like region expanded towards both surface sides with the polyethersulfone content. The 4CHF-S2 membrane was obtained by using ethanol as internal coagulant while water as external coagulant. And the 4CHF-S3 membrane was achieved by using ethanol as internal coagulant while water as external coagulant. The typical 4CHF-S1, 4CHF-S2 and 4CHF-S3 membranes exhibited pure water fluxes of 3.38, 3.34 and 3.74 m³ · m⁻² · h⁻¹ and fracture loads of 20.86, 20.08 and 18.12 N, respectively.