Influence of the dilute-solution properties of cellulose acetate in solvent mixtures on the morphology and pervaporation performance of their membranes

The pervaporation performance of cellulose acetate (CA) membranes prepared from acetone (AC), acetone/tetrahydrofuran (AC/THF), acetone/chloroform (AC/CF), and acetone/cyclohexane (AC/CYH) was studied for separating MeOH/MTBE (methyl tert-butyl ether) mixture with 5 (wt) % MeOH. The dilutesolution properties and Huggins constant (KH) of CA dissolved in AC and AC/solvent mixtures with 15 vol % of the second solvent (tetrahydrofuran, chloroform, or cyclohexane) were examined. J and of the CA membranes were affected by the types of solvent mixtures used to prepare the casting solutions. Under the same conditions, the membrane with AC/CYH had the highest J value and the lowest (alpha)value, and it was followed by the membranes with AC/CF, AC/THF, and AC. The increasing value of J and decreasing value of (alpha)for the CA membranes from different solvent mixtures were in good agreement with the increasing value of KH of CA in corresponding solvent mixtures. Furthermore, differences in the morphology from scanning electron microscopy images of the cross sections or from atomic force microscopy photographs of the surfaces of the membranes existed, and they provided proof of the different pervaporation performances of the CA membranes prepared from AC and AC/solvent mixtures.