Boron rejection by cellulose acetate reverse osmosis membranes

Abstract The rejection of boric acid by different types of reverse osmosis membranes has been measured. At 102-atm applied pressure, the rejection was about 56% with modified cellulose acetate membranes of the Loeb-Sourirajan type and about 67% with cellulose triacetate membranes. Boric acid permeability measurements carried out with dense cellulose acetate membranes show that the transport properties of these membranes are somewhat different from those of the thin solute-rejection layer on the modified membranes, and that solvent-solute flow coupling is observable in this system. Certain additions to the feed solution were found to enhance boric acid rejection by complex formation, and results obtained with mannitol additions are consistent with the known complex-formation equilibria.