Polar and steric effects in reverse osmosis

Abstract The effects of polar parameter Σσ * and steric parameter Σ E s on reverse osmosis separations of alcohols, aldehydes, ketones, and ethers (noncyclic) in aqueous solutions involving single solute systems and porous cellulose acetate membranes are discussed. The least‐squares and multiple‐regression analyses of solute transport parameter data show that the separation of aldehydes, just as that of alcohols, is predominantly a function of Σσ * , and that of ethers is predominantly a function of Σ E s , whereas that of ketones is best represented as a function of both Σσ * and Σ E s . The results also indicate that even where water is preferentially sorbed at the membrane solution interface, solute separation in reverse osmosis is affected by the nonpolar character of the solute molecule. A general expression for solute transport parameter in reverse osmosis is presented for further study.