Preparation and characterization of novel acetylated cellulose ether (ACE) membranes for desalination applications

Acetylated cellulose ethers (ACEs), a new family of cellulosic polymers, were synthesized via the esterification of hydroxyl alkyl cellulose (HAC). The average molecular weight of the ACEs was in the range 220–280 kDa, much higher by an order of magnitude than that of cellulosic polymers commonly used for membrane materials, thereby giving rise to better physical and chemical properties than conventional cellulosic polymers. Dense ACE membranes were first prepared to study fundamental transport behaviors in terms of the permeability, the apparent diffusion coefficient and the solubility coefficients of water and salt (e.g., NaCl). The water permeability and salt passage in ACE membranes were comparable with other cellulosic polymers such as cellulose acetate (CA) and cellulose triacetate (CTA), based on the trade-off relation between water permeability and water/salt selectivity. Novel ACEs showed good solubility in common organic solvents such as dimethylformamide (DMF), dimethylacetamide (DMAC), and N-methyl-2-pyrrolidone (NMP), leading to easy membrane fabrications in various membrane structures, e.g., ACE thin-film composite (TFC) membranes (as a selective thin layer), and microporous asymmetric ACE membranes (as a microporous supporting layer). In this study, such various membrane structures were investigated by using novel cellulosic polymers, ACEs, and then they were evaluated for potential desalination applications such as reverse osmosis (RO) and forward osmosis (FO).