Rejection of inorganic salts by charged ultrafiltration membranes made of sulfonated polysulfone.

Abstract

A charged ultrafiltration membrane made of sulfonated polysulfone is used to separate 10 inorganic solutes. Rejections are high when solute concentration is low, and become lower with higher concentration, which is the typical trend of the charged membrane. Thus the charged membrane can remove low content of inorganic solute at low pressure of ultrafiltration range, resulting in energy saving. Reflection coefficients and solute permeabilities are determined as functions of concentration and these are compared with the values predicted by the theoretical treatment developed here on the basis of the frictional interpretation. The osmotic coefficients of membranes are determined by use of the reflection coefficient, and are then used to calculate solute permeabilities. Though the theory predicts lower permeability at low concentration, general coincidence of theory and experiment is good. By using this result the characteristics of the charged membrane can now be estimated.