Preparation of porous mullite ceramic supports from high alumina fly ash

With the aid of dry pressing method, porous mullite ceramic supports were prepared successfully using desiliconized high alumina fly ash as main raw material, kaolin and alumina as auxiliary raw materials, and spherical graphite as pore-forming agent. The microstructure, bulk density, apparent porosity, water absorption, flexural strength and permeability of the ceramic supports were affected by the graphite dosage, sintering temperature and time. The mullite ceramic support with the addition 30 wt% graphite and sintered at 1400 degrees C for 2 h achieved the optimum comprehensive performances, whose apparent porosity, flexural strength and permeation flux achieved 55.7%, 8.5 MPa and 3.65 mL cm(-2) min(-1), respectively. After spin coated with the mixing sols of silica and alumina, and calcined at 1300 degrees C for 1 h, a layer of integrated and smooth mullite ceramic membrane was loaded on the support, and it attained the permeation flux of 3.41 mL cm(-2) min(-1). The obtained porous mullite ceramic support and membrane could be used as the filter materials for waste water treatment. This work is not only conducive to eliminate the environmental pollution caused by coal fly ash, but also save the resources, such as clay and alumina.