Rejection of poly(ethylene glycol) molecules by an ultrafiltration membrane

The theory of reverse-osmosis separation was used to describe the rejection of poly(ethylene glycol) (PEG) molecules (molecular weight 1500–20 000) by ultrafiltration membranes.

Comparison of experimental data with theory allows us to obtain parameters such as the equilibrium partition coefficient γ, pore radius, thickness and porosity of the active layer of the membrane, coefficient of diffusion, and the thickness of the layer of concentration polarization. The optimum conditions for ultrafiltration are considered.

Rejection of PEG molecules may be explained in terms of the theory of surface forces by the action of forces of structural repulsion. Using the DLVO theory, the optimal pore sizes for charged membranes were estimated.