Ceramic membranes are porous inorganic separation layers in which a metal oxide, carbide or nitride forms the selective barrier ^[1]. The support is a coarse asymmetric body of compatible ceramic, and successive coating and firing steps deposit layers of decreasing pore size, so the structure is graded from a macroporous support to a microporous skin ^[1]. Alumina, zirconia, titania and their mixtures set the chemical and thermal envelope, because the oxide decides resistance to acid, to alkali and to temperatures above those that polymer membranes tolerate ^[2]. Pore size and its distribution, not a dense lattice, separate the ultrafiltration and microfiltration grades from dense ceramic electrolytes ^[3]. The oxide surface carries hydroxyl groups and a pH-dependent charge, so ionic retention also depends on the electrolyte ^[1].