EVALUATION OF DEAD-END ULTRAFILTRATION PROPERTIES BY ULTRACENTRIFUGATION METHOD

In protein ultrafiltration, solution environment factors such as pH an d solvent density are important in controlling the filtration flux. Al so. the properties of the filter cake of macromolecular solutes formed on the membrane surface play a vital role in determining the filtrati on flux in ultrafiltration. On the basis of the sedimentation velocity technique and the high-speed sedimentation equilibrium technique usin g an analytical ultracentrifuge, the influence of the protein solution pH on the time variation of the filtration flux in unstirred dead-end ultrafiltration was accurately described. It was clearly demonstrated that the low filtration flux around the isoelectric point is mainly d ue to the build-up of compact filter cake, which causes a large hydrau lic How resistance. Furthermore, it was shown that the solvent density rho has a large effect on the dynamically balanced filtration rate in upward ultrafiltration just as it does on the sedimentation coefficie nt in ultracentrifugation.