Preparation of cordierite-based porous ceramic micro-filtration membranes using waste fly ash as the main raw materials

Cordierite-based porous ceramic micro-filtration membranes were prepared on tubular macro-porous cordierite supports using waste fly ash and basic magnesium carbonate as the starting materials by spray-coating, followed by dip-coating for modification. Optimization of the raw materials ratio was found to be necessary to avoid crack formation during sintering, which is demonstrated by the sintering shrinkage behavior of the samples with different basic magnesium carbonate content. Crystallization phase development of the prepared membranes was studied by XRD and TG/DTA. The results confirm that α-cordierite was formed above 1100 °C and that its crystallinity improved steadily with further increasing firing temperature. Furthermore, microstructure, pore properties and gas permeation flux of the membranes were investigated. The preferred sintering temperature for the tubular membranes was in the temperature range of 1150–1200 °C based on the results of XRD, SEM, pore-structure and nitrogen permeation. Cordierite-based porous membranes with average pore size in the range of 3.6–6.4 μm and nitrogen permeance of (7.52–9.82) × 104 m3 m−2 h−1 MPa−1 under the average pressure of 0.15 MPa have been obtained, which can be controlled by adjusting the sintering regime.