A NEW MODEL FOR THE CALCULATION OF THE LIMITING FLUX IN ULTRAFILTRATION

The occurrence of the limiting flux in ultrafiltration is elucidated w ith the formation of a cake (gel) layer on the membrane surface. Befor e cake formation, the pressure drop on the concentration polarization layer, as well as the permeate flux, increases with the applied pressu re. The pressure drop on the concentration polarization layer, however , will no longer change with the applied pressure after the formation of the cake layer. The limiting flux will be obtained if the hydrodyna mic conditions in the filtration channel are not affected by the cake layer. A mechanistic model for predicting the limiting flux in ultrafi ltration is developed. A procedure to correlate the model with experim ental ultrafiltration data is also presented. (C) 1998 Elsevier Scienc e B.V.