Visualization and modelling of the polarization layer and a reversible adsorption process in PEG-10000 dead-end ultrafiltration

Real-time holographic interferometry has been used to visualize the evolution of the polarization layer during dead-end ultrafiltration of PEG-10000. Several experiments at a constant pressure of 1 bar and varying the feed concentration of PEG-10000 (5–12.5 kg/m3) have been carried out. In all the experiments it has been possible to follow the appearance, evolution and disappearance of the polarization layer. Experimental results have also shown evidence of the existence of a reversible adsorption process on the membrane surface. A mathematical model has been proposed for the simulation of the dead-end UF process. This model, based on the convection–diffusion mechanism and the osmotic pressure theory, has been combined with an empirical equation for the adsorption process. The model has been validated, under the experimental conditions used, by a reasonable agreement between experimental and calculated results (concentration profiles and permeate flux).