Study on Reverse Osmosis. The Permeation Behavior of Amino Acid Solutions through Cellulose Acetate Membranes

Transport phenomena of some aliphatic amino acids and aminobenzoic acids were investigated with Loeb type membranes annealed at 60–80°C. The quantitative relation between permeability through the membrane and dissociation of amino acid was examined. The charged species are rich in the solutions of amino acids such as l-leucine, l-alanine, and l-glutamic acid, regardless of the pH of solution, thus making the rejection by membranes large; the rejection of l-leucine which had a rejection of 35% for NaCl, was 63.2% even for the membrane cured at 60°C. On the other hand, for aminobenzoic acids, the number of uncharged species in solution varied with the change in pH, and the rejection varied with pH. The fluxes of aminobenzoic acids were in linear relation to the calculated amount of uncharged species. The results of adsorption experiments indicate that the amounts of adsorbed aminobenzoic acid to cellulose acetate were in logarithmic relation to calculated amounts of undissociated species. The results support the view that dissociated species are more difficult to be distributed in membrane than undissociated ones.