Fabrication and characterisation of hollow fibre ceramic membranes from fly ash

Abstract

The development of ceramic membrane to treat wastewater is generally limited due to the fact that materials commonly used for fabrication of these membranes such as high purity alumina (e.g. Al₂O₃) are expensive. Thus, the aim and purpose of this present work is to fabricate and characterize low-cost ceramic membranes using abundant and low-cost fly ash as the raw material. However, the presence of unburnt carbon in fly ash would significantly increase membrane porosity which would affect the mechanical strength and removal efficiency. Thus, it is of paramount importance to determine the optimum loading of fly ash during preparation of precursor solution. In the present work, the membrane precursors were prepared using three different fly ash loadings, i.e. 40wt%, 45wt%, and 50wt%. The membranes were fabricated via phase inversion technique and sintered at 1250°C. The membranes were then characterised in terms of its density, shrinkage, volumetric porosity, mechanical strength, and equilibrium water content. The results obtained show that at 45wt % loading, the membrane produced exhibited optimum properties with percent shrinkage, density, and bending strength of 52%, 1.28g/cm³, 37MPa, respectively. The higher shrinkage of 45wt% loading membrane as compared to other loadings also affects the cross-sectional morphology of membrane, exhibiting a spongy structure with smaller macrovoids at an average pore size of 7.8µm. In addition, the 45wt% loading membrane was also less porous as compared to other membranes, with 26% porosity and 39% to achieve equilibrium water content.