Modification of ceramic membranes by alcohol adsorption

This study aims at modifying ceramic membranes by means of alcohol chemisor ption. Composite ceramic membranes with a skin layer of gamma -alumina were used. First, the adsorption of several alcohol on powdered gamma -alumina was investigated emphasising the thermal stability of the adsorbed compound s. Later, a commercial gamma -alumina membrane was modified by alcohol adso rption. The permeability of water and several organic compounds was obtaine d for both the non-modified and modified ceramic membrane. Also, its isoele ctric point was determined. The results prove that all the alcohol were rea dily adsorbed on powdered gamma -alumina not only physically but also chemi cally forming an alkoxide. The chemisorbed alcohol was stable up to 200 deg reesC. Beyond this temperature, the alkoxide breaks up releasing the alcoho l although the alkoxide also can react yielding an olefin or ether. The cer amic membrane was also successfully modified by alcohol adsorption. The lay er of chemisorbed alcohol imparts hydrophobic characteristics to the membra ne surface, so water permeability decreases significantly. This cannot be m erely explained by pore size reduction due to the adsorbed layer. Thermal t reatment at 250 degreesC recovered original permeability with only minor da mage to the membrane. (C) 2002 Elsevier Science B.V. All rights reserved.