Polymer membranes with differing degrees of hydrophilicity were prepared from mixtures of cellulose acetate butyrate and cellulose acetate hydrogen phthalate. The degree of hydrophilicity was determined from measurements of water uptake and the apparent water diffusion coefficient. The transport properties of sodium dodecyl sulfate through these membranes were studied by measuring permeability using the time-lag technique. The mutual differential diffusion coefficients of the surfactant are 1-2 orders of magnitude lower than in aqueous solution. The permeability and partition coefficients between the aqueous subphase and membranes were found to depend on the hydrophilicity of the polymer blend, but to be virtually independent of temperature. Possible applications of these systems in surfactant purification are suggested.