(227c) Modeling Permeate Flux in Ultrafiltration of Non-Newtonian Polysaccharide Solutions

Michelle C.
Almendrala^*, 1,  Shang-Tian
Yang², Jonathan L. Salvacion³

¹School of Chemical Engineering and Chemistry,
Intramuros, Manila, Philippines 1002
²Department of Chemical and Biomolecular Engineering,
Columbus, Ohio, USA 43210
³Department of Chemical Engineering, University of the
Philippines, Diliman, QC, Philippines^*e-mail: michael.almendrala@yahoo.com

Abstract
           

The development of mathematical  models for permeate flux behavior  of non-Newtonian polysaccharide solutions in
ultrafiltration has been studied using hollow fiber membrane modules. The gel
polarization model was modified to express the permeate flux as function of the
operating parameters. The modified gel model integrating the average wall shear
stress per unit length of the membrane (g_W /L) has been
proposed to predict permeate flux. Two empirical equations based on the
modified gel polarization model were also developed to express the dependence
of the resulting permeate flux on the properties of the solution and
operational variables. These correlations were able to predict the permeate
flux behavior on the assumptions made for the constant and variable gel layer
concentrations. An empirical model was also developed incorporating the factors
affecting flux. The developed model is capable of predicting the dependence of
the permeate flux on operating conditions and solution properties. It was
demonstrated in this model that the effects of temperature, concentration,
transmembrane pressure, shear rate and pH on permeate rate are interdependent.
For all these models, the resulting permeate fluxes have been shown to be
controlled primarily by the wall shear rate or the feed flowrate. Achievement
of high fluxes depends therefore, upon operating at flow conditions that
maximize the rate of mass transfer from the membrane surface. In laminar flow
systems, this is achieved by operating at high fluid velocities across the
membrane surface.The predicted results based from the mathematical models were
similar and found to be in good agreement with the experimental data.
Keywords: ultrafiltration; permeate
flux; gel polarization