Effect of Moisture on and Kinetic Features of the Ultrafiltration Rate of Dialysis Membrane

The kinetic features of ultrafiltration of cellulose dialysis membrane stored under various humidity and temperature conditions were studied to obtain basic information of shelf-life characteristics of dialyzers. The ultrafiltration rate (UFR) decreased with time and the UFR-time curve suggested that the UFR would approach a certain equilibrium value. This phenomenon could be simulated well by the following equation: UFR = a.b.t/(1 + a.t) + c, where a, b, and c are constants and t is time. The effect of moisture adsorption onto the membrane on the UFR is discussed. A hypothesis is that in the amorphous region of cellulose, adsorbed water molecules would serve as molecular crosslinks through hydrogen bonding, and as this would reduce size of fine pores in the amorphous region, the UFR decreases.