Porous MgAl 2 O 4 filters were prepared by reactive sintering of a MgCO 3 (basic) powder and 4-type Al 2 O 3 source powders with different particle size and phases (-Al 2 O 3 , fine and coarse boehmite AlOOH, and -Al 2 O 3). The mixed powder compacts were reactively sintered in air at 1200, 1400 or 1600 °C for 2 h to obtain MgAl 2 O 4. Single-phase porous MgAl 2 O 4 was successfully obtained by the reactive sintering at 1400 and 1600 °C. From the SEM observation, the initial particle sizes of Al 2 O 3 sources strongly affected the final microstructure of porous MgAl 2 O 4 , rather than the phases of Al 2 O 3 sources. The porous MgAl 2 O 4 filter made from fine boehmite source exhibited good performance to remove submicron-sized colloidal particles (simulating bacteria) from a suspension. Possibility of the thermal recovery of porous MgAl 2 O 4 filter was demonstrated.

Porous ceramic filters made of MgAl 2 O 4 spinel are promising due to their excellent thermal and chemical stability. In this study, toward future cross-flow ultrafiltration applications, reactive synthesis of porous MgAl 2 O 4 membranes on a macroporous Al 2 O 3-based ceramic tube has been examined. Fine (0.2¯m) and coarse (0.7¯m) ¡-Al 2 O 3 powders and two types of MgO sources, i.e., MgO (³2.8¯m) and MgCO 3 (basic) [hydromagnesite Mg 5 (CO 3) 4 (OH) 2 •4H 2 O] (³5.5¯m) powders were used as starting materials for the reactive synthesis of porous MgAl 2 O 4 membranes. For the intermediate layer, MgCO 3 (basic) powder was favorable as a MgO source because it can clog up the large (15¯m) pores in the Al 2 O 3-based tube. Meanwhile, for the top layer, MgO powder with finer particle size was favored to obtain homogeneous layer for ultrafiltration.