Micro-channel enhanced alumina membranes - designing and tailoring their properties for widened applications

摘要

Ceramic membranes have the potential to replace polymeric membranes in existing membrane processes as well as expanding their applications to unexplored territories. However, they only hold a small market share out of all the other membrane materials, and the main deterrents are high capital costs, lower performance, and brittleness. Hereby, in this thesis, significant progress has been made addressing the above-mentioned bottlenecks. By using the micro-channel inducing combined phase inversion and sintering method, ceramic asymmetric membranes with greatly enhanced performance and widened applications were fabricated. udFirstly, improved understanding of the formation mechanisms of these micro-channels was achieved by fabricating alumina disc membranes. Parameters such as: suspension composition, membrane width, and coagulation temperature were manipulated and a wide range of different micro-channels were formed. The microfiltration membranes with the long and cylindrical micro-channels exhibited the highest water permeation flux and can be potentially used in water treatments. Furthermore, the micro-channel properties were mimicked using the Rayleigh-Taylor Instability.udNext, six hollow fibre cross-section morphologies were designed and delivered via the use of different bore fluids, air gap, and polymer sacrificial layers in order to control the surface at which the micro-channels are open at. Apart from improving permeation flux, the opening of the micro-channels allows access to these pockets of space, which can be used to store and pack functional materials to form highly compact systems. The presence of micro-channels compensates the membranes’ mechanical stability, and therefore, a method for improving mechanical stability was put forward: to form multi-channel hollow fibres, tubes or monoliths with a plurality of micro-channels and increased cross-section area. The resultant membranes exhibited improved bending strengths. Finally, a potential new application of the hollow fibre with open micro-channels was studied. Adsorbents were packed into the micro-channels, to form a hollow fibre GC column perform oxygen and nitrogen separation, and an 8 m long column managed to separate the two components.