1977 Volume 50 Issue 6 Pages 317-322
The permeation characteristics of cellulose nitrate (CN) -cellulose acetate (CA) blend polymer membranes were investigated by changing membrane preparation methods and permeation condition. The casting solutions were prepared from mixtures of CN-CA, acetone (A), and formamide (FA) in the proportion of 13 : 45 : 42 (wt%). When the CN/CA ratios were varied, there was a maximum value in pure water permeability, and the blend composition having the maximum permeation rate changed with the solvent evaporation period during membrane formation. However, when the aqueous solutions of poly (ethylene glycol) were used as feed, the permeation rates were increased with an increase in the content of cellulose acetate in the blend polymer. In the case of using the aqueous solution of poly (vinyl alcohol) as feed, the permeation rates had the maximum value at the ratio, CN/CA =1/2. From these results, it was found that the fine structures of blend polymer membranes were influenced by the ratio of blend polymer composition and the solvent evaporation period and the interaction between the membrane substrate and the solvent and solute in the feed, also affected the permeation characteristics. The permeation rate was increased with an increase in the operating pressure up to 4 kg/cm2but over 4 kg/cm2the rate began to decrease. The permeation rate was decreased with an increase of the feed concentration and increased with an increase of the operating temperature. These phenomena were discussed from a point of view of the physical and chemical natures of the membrane substrate and feed.