Characterization of the firing behaviour of an illite-kaolinite clay mineral and its potential use as membrane support

The commercial value of any clay depends on its physical and chemical properties, these could help in tuning the characteristics of ceramic membrane supports required at extreme filtration conditions. The characteristics of two clay minerals named SA and CH were studied at various firing temperatures. The composition in oxides of both raw materials consisted of quartz (44.40 ± 0.60 to 46.98 ± 0.57 m%), alumina (13.16 ± 0.56 to 19.64 ± 0.48 m%), iron oxide (4.85 ± 0.46 to 6.37 ± 0.70 m %), and relatively smaller amounts of alkaline-earth oxides (3.34 ± 0.43 to 5.98 ± 0.33 m% calcium oxide and 1.98 ± 0.18 to 5.87 ± 0.34 m% for magnesium oxide). XRD of the investigated samples indicated the presence of kaolinite and illite as pure clay fractions in the clay mineral. SEM showed that the clay minerals were constituted from fine poorly crystalline particles with particles’ size more than 5 μm. The specific surface areas of the clay minerals were found to vary between 94.5 ± 6.3 to 138.6 ± 4.2 m(2)/g using methylene blue stain test, indicating that, the clay minerals fall within chlorite, illite, and kaolinite categories. The porosity of the clay supports made from both clays were found to be maximal with values of 23.45% ± 0.66 and 21.61% ± 0.60 for SA and CH clay materials respectively at 700°C. These values were a direct result of capillary movements of water in the specimen pores that were opened to the outside leading to the highest number macropores and mesopores in the specimen.