Clean Technology 2010

Ion Rejection Properties of Nanofiltration Membranes With Inhomogeneous Charge Distribution

A. Szymczyk, H. Zhu, B. Balannec
University of Rennes, FR

Keywords: nanofiltration, modelling, charge distribution, ion rejection

Abstract:

Ion rejection properties of NF membranes with inhomogeneous fixed charge distributions are investigated theoretically. It is shown that the occurrence of spatial inhomogeneities in the fixed charge concentration may lead to an enhancement of the salt rejection with respect to a homogeneously charged membrane. Moreover, membranes with appropriate bipolar charge distributions can lead to similar rejections for both 2-1 and 1-2 asymmetric electrolytes. These performances cannot be achieved with homogeneously charged membranes since the Donnan theory predicts that the membrane strongly rejects electrolytes with divalent coions but is much more permeable to electrolytes with divalent counterions. These findings suggest that designing advanced membranes with controlled distribution of surface groups could be of great interest for desalination and water treatment.
 
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