Abstract
For the purpose to standardize method to determine molecular weight (Mw) cutoff characteristics of ultrafiltration (UF) membrane using aqueous polyethylene glycol (PEG) solutions, the effect of operating conditions of linear velocity and transmembran pressure (TMP) on PEG retention was investigated. Thin channel type cells were made, of which dimensions were width 4 [min], length 79-118 [mm], depth 0.7-1.4 [mm] and effective membrane area 3.48-4.72 [cm2], Based on velocity variation method, mass transfer coefficients on the surface of membrane (k) were calculated, which agree well with that based on boundary layer theory when Mw of PEG is less than 3 [kg·mol-1] and with that obtained by Leveque's equation when more than 7.5 [kg·mol-1]. Using the calculated k, intrinsic retention of membrane was obtained, which is increasing with the increase of TMP, but which is independent on linear velocity on the surface of membrane.
NTU-3150 which is made of polysulfone and supplied from Nitto DENKO Co. has intrinsic retention of 95% at Mw 15 [kg·mol-1] at 20kPa of TMP. DUS-40 which is made of polyethersulfone and supplied from Daicel Chemical Ind. Ltd. has intrinsic retention of 95% at Mw 10 [kg·mol-1] at 35 kPa of TMP-and 20 [kg·mol-1] at 10 kPa. With the increase of TMP, curves of intrinsic retention vs Mw shift to the left and becomes upright.
