Abstract
To evaluate the high-performance of membrane materials in the concentration of an aqueous solution of dilute bioethanol under temperature-difference controlled evapomeation (TDEV), asymmetric porous cellulose nitrate (CN) and cellulose acetate (CA) membranes were prepared by a phase inversion method. In the concentration of dilute ethanol under TDEV, these membranes showed a high permeation rate and high ethanol/water selectivity. In membranes with almost the similar pore size, the ethanol/water selectivity was considerably higher for the CN membrane than the corresponding CA membrane. This result suggested that the affinity between the membrane material and the permeant is an important factor in the separation selectivity.
Highlights
Ethanol that can be produced by biomass fermentation is a clean energy source, but typically its concentration is about 10 wt% in aqueous solution
As the amount of non-solvent is increased, the average pore diameter of the asymmetric cellulose acetate (CA) membrane increases remarkably, whereas that of the asymmetric cellulose nitrate (CN) membrane hardly changes. These results suggest that the formamide added to the casting solution in preparation of the CA membrane is effective as a non-solvent in relation to CA
When asymmetric porous CN and CA membranes were applied to temperature-difference controlled evapomeation (TDEV) in the concentration of an aqueous ethanol solution, a high permeation rate and high ethanol/water selectivity were obtained
Summary
Ethanol that can be produced by biomass fermentation is a clean energy source, but typically its concentration is about 10 wt% in aqueous solution. We have been studying the permeation and separation characteristics of aqueous ethanol solutions passed through various hydrophilic and hydrophobic polymer membranes. Hydrophilic membranes can selectively remove water from aqueous solutions of high ethanol concentration [1,2,3,4,5,6], whereas hydrophobic membranes allow ethanol permeation from aqueous solutions of dilute ethanol [7,8,9]. We describe in detail the permeation and separation characteristics of asymmetric porous CN and CA membranes during TDEV of an aqueous solution of dilute ethanol, and discuss the results in terms of the physical and chemical structures of the cellulose ester membranes
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