Separation of Aqueous Ethanol Solution by Pervaporation using Uniplanar-Oriented Carboxymethyl Cellulose Membranes

Abstract

Uniplanar Oriented carboxymethyl cellulose (CMC) membranes were prepared by the simultaneous-biaxial (SB) stretching method under swollen conditions in the wet process, where CMC molecules were randomly oriented within the membrane along parallel to the membrane surface, as reported previously. Then, separation of aqueous ethanol solutions by pervaporation through the uniplanar-oriented CMC membranes was investigated. Permeation rates (flux) of the uniplanar-oriented CMC membranes were considerably higher than those of unstretched membranes. On the contrary, separation factors decreased with increasing degree of uiplanar orientation. Furthermore, the effect of uniplanar orientation on pervaporation was discussed in relation to molecular structure of CMC and affinity of the CMC membranes to ethanol and water. CMC-H and CMC-H-SB membranes were prepared by converting CMC-Na and CMC-Na-SB to their H-type in aqueous ethanol solution. Similarly, CMC-Li. CMC-K, CMC-Li-SB and CMC-K-SB membranes were prepared from CMC-Na and CMC-Na-SB. These membranes were effective in selective separation of water from aqueous ethanol solutions by the pervaporation technique. Particularly, in the case of CMC-Na-SB membranes, the flux was similar to that of CMC-Na membranes, but permeation of ethanol from the aqueous ethanol solutions was not observed.