Reactive synthesis of porous MgAl₂O₄ membranes on a macroporous Al₂O₃-based ceramic tube toward cross-flow ultrafiltration

Abstract

Porous ceramic filters made of MgAl₂O₄ spinel are promising due to their excellent thermal and chemical stability. In this study, toward future cross-flow ultrafiltration applications, reactive synthesis of porous MgAl₂O₄ membranes on a macroporous Al₂O₃-based ceramic tube has been examined. Fine (0.2 µm) and coarse (0.7 µm) α-Al₂O₃ powders and two types of MgO sources, i.e., MgO (∼2.8 µm) and MgCO₃ (basic) [hydromagnesite Mg₅(CO₃)₄(OH)₂·4H₂O] (∼5.5 µm) powders were used as starting materials for the reactive synthesis of porous MgAl₂O₄ membranes. For the intermediate layer, MgCO₃ (basic) powder was favorable as a MgO source because it can clog up the large (15 µm) pores in the Al₂O₃-based tube. Meanwhile, for the top layer, MgO powder with finer particle size was favored to obtain homogeneous layer for ultrafiltration.