Crossflow ultrafiltration of cake forming solutes:: a non-steady state model

The aim of this work was to check the validity of a non-empirical non-steady state model, which was initially developed to predict permeate flux for dead-end ultrafiltration, in the crossflow ultrafiltration of macromolecules. All the model parameters were theoretically calculated. Consequently, the model is capable of making predictions without the need of experimentation. The results estimated by the model were compared with those experimentally obtained in an ultrafiltration pilot plant. Tests were performed with Carbosep M2 ceramic membranes (Orelis, France) at different transmembrane pressures (0.1, 0.2, 0.3 and 0.4 MPa) and crossflow velocities (1, 2 and 3 m/s). Polyethylene glycol of 35,000 g/mol was used as a standard macromolecule in the fouling experiments. The validity of the model is restricted to the case when cake layer formation is the fouling mechanism. Model predictions are in agreement with experimental results for a crossflow velocity of I m/s, when the fouling mechanism is more likely to be cake formation. For other fouling mechanisms the predictions are not so good.