Potentiality of organic solvents filtration with ceramic membranes. A comparison with polymer membranes

The objective is to identify the main interfacial interactions influencing the flow of organic solvents through ceramic oxide membranes exhibiting a submicronic porous structure, in particular ceramic nanofilters. Three microporous (r(p less than or equal to) 1 nm) composite ceramic oxide membranes (3Al(2)O(3)-2ZrO2, SiO2-ZrO2, SiO2-TiO2) prepared by the sol-gel process were investigated. Permeation experiments were operated with polar (ethanol) and non-polar (hexane, heptane, toluene) organic solvents. Ceramic oxides are considered as high energetic surfaces for non-polar liquids leading to attractive interactions and stable substrate-wetting films when epsilon(1) < epsilon(s). In the case of a porous substrate, capillary pressure is the parameter generally used to account for liquid penetration in the pores. For submicronic pore sizes, an additional contribution to the surface energy (the disjoining pressure or the fluid density variation resulting from molecular ordering of solvent molecules at solid interfaces) may explain observed deviations to the Darcy's law. Results are in good agreement with these interfacial energy concepts. The specific permeation observed for each solvent/membrane pair could be explained by the relation existing between the acid-base surface properties of ceramic oxides and the solid surface energies.