Preparation and Characterization of Novel Acetylated Cellulose Ether Membranes for Desalination Applications

   Organic-soluble acetylated cellulose ethers (ACEs), a new family of cellulosic polymers, were synthesized via the esterification of hydroxyl alkyl cellulose, a water-soluble cellulose ether. The weight average molecular weight of ACEs prepared in this study is as high as 220 - 280 kDa, which is higher by an order of magnitude than that of common cellulosic polymers used for reverse osmosis and ultrafiltration membranes, thereby expecting better chemical and mechanical properties than conventional cellulose derivatives. Dense and asymmetric membranes using the ACEs were prepared to investigate the permeability, the diffusivity and the partition (solubility) coefficients of water and salt in ACE and also to evaluate the availability as microporous supporting layers for thin-film composite membranes. The fundamental transport properties of ACE membranes were compared with other cellulosic membranes such as cellulose acetate and cellulose triacetate usually used as desalination membranes, in terms of correlation between permeability and water/salt selectivity. Thin-film ACE composite membranes were also prepared and evaluated for reverse osmosis applications. The coated CA and ACE active layers followed the trade-off relationship. The coating solution concentrations of AMCs which shows similar water flux with CA were 4-5 times lower than CA due to high molecular weight and viscosity of AECs. From these results, we suggest that ACE is a good candidate for desalination applications with high water permeability and water/salt selectivity.