An improved method is presented for describing the apparent intrinsic pore properties (mean pore size and pore size distribution) of ultrafiltration membrane from solute rejection curves. To obtain the apparent intrinsic pore properties, firstly the mean pore diameter is determined from the solute rejection curve by correcting the steric and hydrodynamic hindrance effect of pores on molecules, and secondly the effects of operating conditions (pressure, feed concentration and recirculation velocity) on the pore properties are examined by ultrafiltration of seven solutes using SEPA-PS-0 membrane and are eliminated by extrapolating to “zero” operating conditions.
The pore property parameters (μ, D_p and θ) obtained from the solute rejection curve are affected by two factors: 1) the plugging of membrane pores by the solute and 2) the deformation of solute due to the variation of pressure and feed concentration. But the recirculation velocity does not affect the pore property parameters. the mean pore diameter is about 60 Å and the pore diameter distribution range is from 30 Å to 103 Å for SEPA-PS-0 membrane at the “zero” operating condition state.