Effects of bentonite concentration on morphology and permeation characteristics of bentonite-doped polysulfone membranes were investigated. Solubility sphere for bentonite was constructed to estimate its solubility parameter. Thermodynamic modeling of phase inversion of this system was carried out using Flory-Huggins theory. The trade-off between thermodynamic and kinetic parameters was used to predict the membrane morphology for bentonite concentration varying from 0 to 5 wt %. The porosity of bentonitedoped membranes decreased up to 3 wt % that increased thereafter. Morphological analysis showed dense cross section with finger-like macrovoids at 3 wt % beyond which it changed to honeycomb structure with large circular voids. Permeability of 3 wt % membrane was the lowest (5.6 × 10 −12 m/Pa s) with 95% bovine serum albumin rejection. Contact angle of the membranes decreased from 83 to 66 with bentonite addition making the membrane more hydrophilic.
A coupled
concentration polarization and pore flow model was used
to predict the transport characteristics of a monovalent salt through
a nanofiltration membrane. The concentration polarization in the flow
channel was modeled using an integral method under the framework of
boundary layer analysis. The extended Nernst–Planck equation
was used to quantify the ion transport through the membrane pores.
Ion partitioning across the solution phase and in the membrane pore
was modeled using the Donnan exclusion principle including the steric
hindrance. The membrane pore charge density was calculated for different
membranes. The contributions of convection, diffusion, and electromigration
toward the solute flux within the membrane pore were estimated. The
calculated permeate flux and the solute concentration in permeate
were compared with the experimental data available in the literature
and were found to be in good agreement, indicating validation of the
developed model.
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