Rejection of dairy salts by a nanofiltration membrane

Abstract

The rejection behaviour of a nanofiltration membrane during the permeation of a salt solution typical of that found in dairy ultrafiltration permeate is described. It was shown that there was no one dominating separation mechanism, but rather the rejection behaviour was a function of both charge interactions and solute size. In simple binary solutions of KCl, it was shown that the pH dependent ion rejection minimum was at a higher pH value than the previously measured surface isoelectric point. This result suggested that the isoelectric point of the internal pore structure was higher than that on the surface. Addition of CaCl2 resulted in the permeation of monovalent salts being highest at t..