A method for prediction of the gel concentration in macromolecular ultrafiltration

A method is proposed for a priori estimation of the important 'gel' concent ration in macromolecular ultrafiltration, which, historically, has always b een calculated by fitting a mathematical model to experimental ultrafiltrat ion data. The method based on the lattice-fluid-hydrogen-bond (LFHB) theory for phase behavior is shown to predict the same qualitative behavior of th e variation of poly-ethylene-glycol (PEG) osmotic pressure with molecular w eight of PEG and its concentration as the experimentally measured trend rep orted in the literature. The solubility limit (lower branch of the binodal envelope) for PEG (6000 kDa) is predicted to be similar to 340 kg/m(3). The corresponding high polymer concentration branch of the binodal is predicte d to be at a polymer volume fraction of 0.84 which is the predicted 'gel' c oncentration for PEG. (C) 2000 Elsevier Science B.V. All rights reserved.