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Evaluation the reflection coefficient of polymeric membrane in concentration polarization conditions
Kornelia Batko1, Izabella Slezak-Prochazka, Andrzej Slezak
1Department of Informatics for Economics, University of Economics in Katowice. kornelia.batko@ue.katowice.pl
Polimery W Medycynie
|July 2, 2013
Summary
The membrane reflection coefficient (sigma) is influenced by solution concentration and boundary layer hydrodynamics under concentration polarization. This finding is crucial for understanding membrane transport where solution homogeneity is challenging.
Area of Science:
- Membrane science and technology
- Physical chemistry
- Biomaterials
Background:
- The reflection coefficient (sigma) is a key parameter in polymer membrane transport.
- Classical methods for determining sigma require eliminating concentration polarization effects, which is difficult in real-world conditions like biological systems.
- Concentration boundary layers form on membranes, complicating transport parameter determination.
Purpose of the Study:
- To investigate if the reflection coefficient (sigma) is affected by solution concentration and hydrodynamic conditions during concentration polarization.
- To assess the influence of concentration boundary layers on membrane transport parameters.
Main Methods:
- Utilized a cellulose acetate hemodialysis membrane (Nephrophan) and aqueous glucose solutions.
- Employed the formalism of nonequilibrium thermodynamics and Kedem-Katchalsky equations.
- Derived mathematical equations to describe the ratio of reflection coefficients under concentration polarization (sigmaS) versus homogeneous conditions (sigma).
Main Results:
- Developed equations relating reflection coefficients under concentration polarization (sigmaS) to those under homogeneous conditions (sigma).
- Identified a bifurcation point in calculated ratios, above which sigmaS depends on solution concentration, membrane configuration, and hydrodynamics.
- Demonstrated that below the bifurcation point, the system's behavior was independent of gravitational direction.
Conclusions:
- The reflection coefficient (sigmaS) of hemodialysis membranes is dependent on solution concentration and hydrodynamic state of boundary layers.
- The value of sigmaS varies with convection type: highest in forced convection, lower in natural convection, and lowest in diffusion.
- The derived equations are applicable to interpreting membrane transport processes where solution homogeneity assumptions are not met.
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