The effect of seasoning a membrane-forming solution on the separation properties of chitosan membranes

The ability to retain hi gh-molecular substances is a basic criterion of me mbrane applicability in the process of ultrafiltration. Separation of high molecular compounds on flat chitosan membranes was investigated. Membranes were produced by the wet phase inversion method, immediately after preparin g the solution and then seasoning for a month. Prior to membrane formation, the change of rheological properties of membrane-fitting solutions was det ermined. Prior to membrane formation, rheological properties of membrane-fo rming solutions were determined immediately after preparing the solution an d after a month seasoning. Testing substances were model proteins: albumin 69 kD, gammaglobulin 159 kD and dextrans 70 and 200 kD, as well as a real s ystem - 1% skim milk solution. The ability to retain proteins was determine d by a standard method which consisted in the determination of retention co efficient. Protein concentration was determined by a spectrophotometric met hod. Dextran separation was determined by the standard method which covered determination of dextran concentration by coulometric titration, and - bec ause of the linear structure of particles and their polydispersity - by gel chromatography through the analysis of molecular weight distribution in th e feed and permeate. Practically, chitosan membranes retain proteins above 69 kD, while dextrans of mass 70 kD are retained in 30%, and these of mass 200 kD in more than 75%. This depends on the linear structure of dextran pa rticles and their significant polydispersity which was confirmed by the chr omatographic analysis. (C) 2001 Elsevier Science B.V. All rights reserved.