SPECIFICATION, SELECTIVITY, AND PERFORMANCE OF POROUS CELLULOSE ACETATE MEMBRANES IN REVERSE OSMOSIS

The general specifications of the Loeb-Sourirajan type porous cellulose acetate membranes are given in terms of the pure water permeability constant, A, and the solute transport parameter, (DAM/Kδ), for sodium chloride at different operating pressures. A scale of membrane selectivity is presented for 12 inorganic and two organic solutes in terms of their relative values of (DAM/Kδ) for several membranes covering a wide range of surface porosities. Using the data on membrane specification and selectivity, and the applicable mass transfer coefficient, k, obtained from a generalized correlation, the performance data for different membranes, solution systems, and operating conditions have been calculated. These data relate membrane specification to membrane performance expressed in simple terms of solute separation and product rate. The effects of variation of (DAM/Kδ), feed concentration, feed flow rate, operating temperature, A-factor (membrane compaction), and chemical nature of solute on membrane performance are illustrated and discussed. The order of solute separation with respect to any two solutes does not always correspond to that of their relative values of (DAM/Kδ), and the former is a function of the latter and the operating conditions of pressure, feed concentration, and the mass transfer coefficient, k. © 1969, American Chemical Society. All rights reserved.