Acetone-stable nanofiltration membranes in deacidifying vegetable oil

The separation of different vegetable oil/solvent. mixtures with two types of nanofiltration membranes was studied. One type had a PEBAX [poly(amide-b -ether) copolymer] top layer, and the other had a cellulose-type top layer. These membranes were stable in acetone, ethanol, 2-propanol, and hexane, a ll important to the oleochemical industry. Permeabilities were highest for acetone, +/-140 L/m(2) . h . MPa, and lowest for hexane, which had negligib le flux at 2 MPa. Permeabilities decreased with increasing triglyceride or free fatty acid (FFA) concentration. Rejection of triglycerides was constan t over the concentration range tested, about 80-95% +/- 5%, depending on th e type of membrane used. These properties make membranes applicable for sep arating triglycerides from acetone by enhancing acetone recovery. Deacidifi cation of triglycerides and FFA mixtures was possible (e.g., fatty acids we re retained less than triglycerides). The permeate consisted almost entirel y of fatty acids in acetone, and only small traces of triglycerides were fo und. This makes it feasible to selectively remove the fatty acids and reduc e toss of triglycerides normally associated with deacidification.