Stability of a Supported Liquid Membrane for Removing Hydrophobic Solutes from Casein Hydrolysate Solution

The stability of a liquid membrane containing a solution of an ionic carrier (Aerosol OT, AOT) in oleyl alcohol and loaded on a commercial support, Celgard 2500, was examined. The experiments were conducted in this flat-sheet support to continuously remove hydrophobic solutes from a feed of casein hydrolysate solution with a strip solution of sodium chloride. Three approaches were investigated to study flux stability of the membrane; i.e., by 1) varying AOT concentrations (10-40% w/w), 2) using a different solvent (decanol instead of oleyl alcohol), and 3) applying an interfacial surface layer on the membrane support. At higher AOT concentrations the flux through the membrane was stable up to 40 hours; the flux declined rapidly beyond this period to about half the initial value and slowly decreased to low values after 120 hours. The use of decanol (100% pure) instead of oleyl alcohol (85% pure) as the membrane solvent increased the flux and improved the stability without significant loss of performance up to about 70 hours. The application of an interfacial gel layer at the feed, strip, or both interfaces did not improve the stability of the AOT/oleyl alcohol membrane. The generation of a polymerized layer at the interface between the organic and aqueous phases of the membrane showed better stability. However, the solute flux through the polymerized membrane was reduced to a low value.