AbstractsEngineering

Membranes are commonly used in industrial separation processes because of their absence of moving parts, simplicity of separation without phase change, potential of scaling and instantaneous response to system variations. In general, polymeric membranes are of low cost and could be easily prepared, yet they fail at processes that involved high temperatures, extreme pH, corrosive and organic chemicals. Ceramic membranes were therefore introduced to these harsh conditions because of their high thermal and chemical stability, while being insensitive to swelling and could be easily cleaned. Industries that make wide use of ceramic membranes include water treatment, chemical production, petrochemical, metal, automotive, textile, pulp and paper, tannery, biotechnology, cosmetic, pharmaceutical, food and beverage. Among all different membrane geometries, hollow fibre has the highest surface area to volume ratio and highest compactness. The major limitation of large scale production and application of ceramic hollow fibre membrane is the brittle nature of ceramic. Brittleness is a significant problem when the membrane is of a hollow fibre geometry which is small in size and has thin walls. Apart from cracking under pressure, brittle ceramic hollow fibre membranes are also difficult to be bundled up and to be sealed into equipment as orientated modules. This thesis presents the fabrication and characteristics of ceramic hollow fibre membranes with enhanced flexural strength, which involves nickel aluminate (NiAl2O4) as a reinforcement medium and as a pure membrane material. NiAl2O4 is a non-toxic ceramic material with high melting temperature and strong resistance to acids and bases. The ceramic nature and stability of the strengthened hollow fibre membrane was therefore maintained. NiAl2O4 was formed by the solid-solid reaction between nickel (II) oxide (NiO) and alumina (Al2O3) at high temperature of 1400 oC or above. All the ceramic hollow fibre membranes were prepared by the phase-inversion and sintering method. Apart from water the commonly used internal and external coagulant in a phase-inversion process, the use of ethanol-water mixture as internal coagulant was also attempted and its effect on the structure of membrane wall was investigated. Brittleness of the ceramic hollow fibre membranes, which was the main focus of this thesis, was indicated by flexural strength obtained by three-point bending test carried out on individual samples. On top of flexural strength, other characteristics of the ceramic hollow fibre membranes that determine their application, effectiveness and efficiency in separation processes were also studied. These include microstructure, porosity, active layer porosity and pore size, pure water flux and chemical stability. All the ceramic hollow fibre membranes prepared were porous, with their pore sizes in the microfiltration range, and are suitable for the separation of solid suspensions from liquid. The study of strength enhancement of porous ceramic hollow fibre membranes started with the…