DEXTRAN SEPARATION FROM SYNTHETIC RAW SUGAR SOLUTIONS BY ULTRAFILTRATION, AND ANALYSIS OF MEMBRANE FOULING MECHANISMS
Keywords:
Dextran, membrane separation, stirred cell ultrafiltration, cake compressibility, foulingAbstract
Dextran separation from synthetic raw sugar solutions was studied using regenerated cellulose and polyethersulfone membranes in stirred and unstirred batch ultrafiltration cells. It was found that the percent rejection of the 5000 molecular weight cut-off regenerated cellulose membrane is larger than that of other membranes investigated, and fouling of the regenerated cellulose membranes occurs more slowly than that of the polyethersulfone membranes. The percent rejection in the membrane separation can be improved by high speed agitation, which is likely due to lower levels of concentration polarization. The permeate flux decay for various transmembrane pressures in both unstirred and stirred filtration was used to predict the mechanism of the membrane fouling. A dextran cake layer is formed in unstirred dead-end filtration, with the cake compressibility in the range of 0.52-0.54, while the complete pore blocking model can be used to describe the fouling mechanism in stirred ultrafiltration. Membrane resistance determination was used for the initial flux data with the result that the resistances of the polyethersulfone membrane and the regenerated cellulose membrane are equal to 1.80 × 1013 m-1 and 3.36 × 1013 m-1 respectively.
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