Mullite whisker-constructed ceramic membranes prepared from fly ash by in-situ catalytic reaction

The industrial application of ceramic membrane in wastewater treatment is usually inhibited by the high manufacturing cost. Here, a low-cost ceramic membrane with whisker-constructed microstructure was prepared using fly ash as the major material and AlF 3 as the catalyst. The influence of AlF 3 contents and sintering temperatures on the synthesis of mullite whiskers and consequently the permeance-selectivity of the whisker-constructed ceramic membrane, was investigated. With the increase of AlF 3 content, the pore-forming mechanism of the ceramic membrane transformed from particles-packing to mullite whiskers-interlocking. The formation and growth mechanism of mullite whiskers were clarified. The formation of silicate liquid-phase during sintering accelerated the shrinkage of the ceramic membrane and merged the short and fine whiskers. For the ceramic membrane with 10 wt% catalyst sintered at 1100 °C, the porosity and average pore size corresponded to 62.3% and 0.41 μm, respectively. Thus, this work provided a strategy for the preparation of mullite whiskers-constructed ceramic membrane with high porosity at low sintering temperature, which facilitated the high-valuable utilization of fly ash spontaneously.