On the Loss of Hydraulic Permeability in Ceramic Membranes

to either aluminum ions or surface hydroxyls and can result in the formation of a surface alkoxide. The properties of inorganic membranes are dependent on the The purpose of this note is to illustrate the effects of heat treatment and surface chemistry of the material, which in turn are affected by chemisorption of organic molecules on the permeability characteristics of parameters such as temperature, pH, and chemisorption of moleporous silica and g-alumina membranes, respectively. In both cases, a cules. For both silica and g-alumina membranes, a significant significant reduction in hydraulic permeability was observed, which has reduction in water hydraulic permeability was observed after heat been attributed to alteration of the membrane surface. Plausible reasons for treatment or exposure to organic solvents. For silica membranes, the permeability loss for both cases, along with the appropriate regeneration the water permeability reduction due to heating at 1407C has been procedures, are discussed. attributed to the removal of physically adsorbed water, which exposes hydrophobic surface patches covered by isolated hydroxyl EXPERIMENTAL groups. In the case of g-alumina membranes strong adsorption of a wide range of organic compounds can result in significant Materials permeability loss. q 1996 Academic Press, Inc.