Ultrafiltration of macromolecular solutions at high polarization in laminar channel flow

Abstract The limiting flux for the ultrafiltration of a macromolecular solute is obtained by a boundary layer integral method for a laminar channel flow with a concentration dependent diffusivity. A simple analytic expression is obtained for this flux which closely parallels the widely used formula of Michaels but with the diffusivity evaluated at the gelling concentration rather than the bulk concentration. Comparison of values given by the analytic result with numerical solutions and experiments show excellent agreement. Flux augmentation experiments carried out with strip type promoters show that at the same flow rate limiting fluxes can be increased to about 3 times the empty channel values.