Micro-structured alumina hollow fibre membranes – Potential applications in wastewater treatment

In this study, three types of micro-structured alumina hollow fibre membranes, i.e. Membranes I, II, and III, have been developed and characterised for potential use in wastewater treatments. They consist of two basic structures: finger-like micro-channels for reduced transmembrane resistance, and sponge-like layer(s) for micro-filtration (MF). They have been fabricated via a combined phase-inversion and sintering technique, whereby the viscous fingering phenomenon that takes place concurrent to phase inversion leads to the formation of a plurality of finger-like voids or micro-channels within the membranes. The three internal coagulants used were hexane, DMSO and tap water with air gaps of 0 or 30 cm. Mechanical strength and water permeation flux were found to be sensitive to changes in membrane morphology, while pore size distribution of the separation layer(s) were less affected and were all in the microfiltration range. Membrane II, with just one very thin separation layer, exhibited the highest water permeation flux of 1874 L/(m2 h) at 0.1 MPa. Effects of sintering temperature on pore size distribution, mechanical property and water permeation of the three membranes, in particular Membrane II, were systematically investigated. Sintering temperatures between 1300 °C and 1350 °C are suggested for Membrane II, taking into consideration of the reduced water permeation at higher sintering temperatures and the lowered mechanical strength at lower sintering temperatures.