LIMITING FLUX IN MEMBRANE SEPARATIONS - A MODEL BASED ON THE VISCOSITY DEPENDENCY OF THE MASS-TRANSFER COEFFICIENT

A hydrodynamic theory is presented to describe the phenomenon of limiting flux in membrane processes. An analysis based upon a development of film theory shows that the variation of viscosity with concentration will, by its very nature, lead to a limiting flux. A previously used relationship between viscosity and concentration is then used to develop a practical version of the limiting condition. The flux-concentration relationship obtained from this relationship is in excellent agreement with the literature. The new model mimics the log-normal relationship over the range for which it is applicable without the need to assume a hypothesized condition such as a gel layer. At present, the model does not include the effect of fouling.