THE EFFECT OF CHARGE-DENSITY ON THE PERMEATING FLUX OF AMINO-ACID THROUGH POSITIVELY CHARGED MEMBRANES UNDER PRESSURE-GRADIENT

Positively charged membranes having different charge densities were pr epared. Ultrafiltration of aqueous amino acid solution was performed a t various values of pH, concentration of amino acid in the feed soluti on, and operating pressure. The effect of charge density of the positi vely charged membrane on the solute flux was examined. Neither the vol ume flux nor the solute flux of amino acid at the isoelectric point wa s affected by the fixed charge of the membrane. On the other hand, bot h the volume flux and the solute flux in pH ranges below and above the isoelectric point decreased with increasing charge density of the mem brane. According to the transport equations with respect to the volume flux and the solute flux, the permeation properties as determined fro m experimental data were successfully evaluated by considering the eff ective charge density of the membrane and the degree of dissociation o f amino acid in pH ranges below and above the isoelectric point.