Transport of Components in the Separation of Ethanol from Aqueous Dilute Solutions by Forward Osmosis

Membrane-based technologies have been considered for separation of ethanol/water mixtures as an alternative to thermal based separations. In this work, we consider forward osmosis (FO) for ethanol separation from aqueous solutions using commercial cellulose triacetate (CTA) and thin film composite (TFC) forward osmosis membranes. Aqueous solutions containing ethanol were used as feed solution and sodium chloride was used as osmotic agent for the tests. The total permeate flux and the reverse salt flux are increased with the increase of the osmotic pressure difference, while the ethanol-water separation factor is decreased. CTA and TFC membranes presented similar total permeate fluxes (from 4 to 8 kg m-2 h-1), but CTA presented lower reverse salt flux (below 5 g m-2 h-1) and higher separation factor (αethanol-water between 1 and 2). Additional tests using reverse osmosis (RO) were conducted to compare with the FO results