SIEVING PROPERTIES OF HEMODIALYSIS MEMBRANES

The ability of hemodialysis membranes to sieve or reject solutes during ultrafiltration has been measured for several solutes and three membranes. The membranes tested included Cuprophan 150 PM, Rhone-Poulenc RP-AN69, and an experimental cellulose acetate (Celanese CA2-3X). Measurements were made in a laminar-flow rejection cell at several transmembrane volume fluxes Jv. Rejection data were corrected for concentration polarization using a thin-film theory. p]Data for Cuprophan were well correlated by the Kedem-Spiegler equation, an exponential form which relates rejection to Jv via the parameters PM (diffusive permeability coefficient) and σ (Staverman reflection coefficient). Another rejection equation, based on linear flux equations, was moderately successful in correlating the data. A pore theory analysis using measured values for σ and PM for Cuprophan implied an effective pore radius of 23 x 10-8cm and an effective area/thickness ratio of 67.4 cm-1. These numbers successfully predicted the observed hydraulic conductivity for Cuprophan. © 1979.