Optimizing the fabrication conditions of monolithic mullite whisker membrane from kaolin and bauxite using the Taguchi method

In this study, low-cost porous mullite whisker membranes were synthesized from kaolin and bauxite, based on a Taguchi design of experiments. AlF3.3H2O and MoO3 were used as additives, and the sintering temperatures ranged between 1100 and 1300 °C. The membranes were subjected to various tests, including XRD, SEM, Mercury, and Archimedes tests, biaxial flexural strength, and permeation measurements of pure water and oily water emulsion. The synthesis conditions were optimized using the Taguchi model and the utility concept. The optimum conditions were found to be 4 wt % of AlF3.3H2O and 6 wt % of MoO3, sintered at 1300 °C, resulting in an apparent porosity of 50.37% and a biaxial flexural strength of 75.21 MPa. SEM images and XRD analysis of the optimized sample showed needle-shaped interlocked network structures with 95.4 wt % of mullite phase. The pure water permeance was measured to be 838.64 L/m2 h bar, and its oil rejection at 3 bar was 95.4%. The monolithic mullite membrane synthesized under optimized conditions in this study exhibited excellent performance and lower production costs in comparison to monolithic ceramic MF membranes produced in previous studies.