Holographic Interferometry Applied To The Measurement Of Boundary Layers In Electrodialysis And Ultrafiltration

Holographic interferometry has been applied to the observation of mass transfer effects in two membrane separation processes : electrodialysis and ultrafiltration. In the case of electrodialysis, a mathematical model has been developed which predicts the form of the concentration profile between the ion-exchange membranes of an electrodialysis unit, as well as the limiting current which flows through the system when the solution concentration at the membrane surface approaches zero. The concentration profiles observed by holographic interferometry have been used to test the validity of the proposed model. Work on a similar comparison of a mathematical model with interferometric observations for the case of ultrafiltration is now under way. Here the results of the measurements are of particular interest, because the nature of the boundary layer is widely disputed.