Application of charged membranes in water softening: modeling and experiments in the presence of polyelectrolytes

In this paper theoretical and experimental results for water softening by b ipolar membranes in the presence of polyelectrolytes have been presented. A modified capillary model is introduced for flow of a multiion solution thr ough the membrane. The most important modifications are: an integral bounda ry condition in Poisson equation and a coupling coefficient in the convecti ve molar flux by using the modified Faxen equation. In addition, electrical permittivity of solution has not been considered as a constant. The predic tions of the model were compared well with the experimental data obtained b y using bipolar membranes in a recirculating test system in the presence of polyelectrolytes. (C) 1999 Elsevier Science B.V. All rights reserved.