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

Abstract

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.

Theoretical Pathway toward Improved Reverse Osmosis Membrane Selectivity for Neutral Solutes: Inspiration from Gas Separations

“…Figure shows preliminary calculations of the diffusivity selectivity ( D w / D s ) of example trace organic contaminants with traditional TFC membranes versus CMS membranes. The diffusivity selectivity was calculated using Maxwell–Stefan equations to convert permeation experimental data for various contaminants in polyamide thin-film composite membranes. − In general, diffusivity selectivity predictions of various contaminants in thin-film composite membranes decrease (move away from the upper bound) as contaminants become smaller and more neutrally charged. The diffusivity selectivities of water versus 2-butanone, ethanol, and o -xylene as estimated with reasonable values based on small pore zeolites using this model are shown as a comparison to those removed with TFC membranes, containing a polyamide layer.…”

Engineered osmosis – sustainable technology for water recovery, product concentration and energy generation

“…Moreover, the process can tolerate feeds with a high level of suspended solids (pulp) and possess better dewatering capacity with lower membrane fouling. 19,20,21 The first recorded FO application in liquid food processing dates back to 1966 for concentrating grape juice using NaCl as the DS. 18 Recently, FO has been explored for concentrating betacyanin from Opuntia ficus-indica, 22 orange juice, 23 watermelon juice, 24 nine different polyphenols, 25 lycopene carotenoid (from watermelon juice), 26 xylose, 27 sugarcane juice.…”

Forward Osmosis as Concentration Process: Review of Opportunities and Challenges

“…This study performed with lower initial alcohol concentration in the feed (5%) described how draw selection can impact relative alcohol/water passage through the membrane, organic draw solutes being preferred to favour alcohol permeation [ 69 ]. The same research team also investigated the impact of membrane type (CTA and TFC membranes from HTI) on the separation process [ 70 ]. The TFC membrane, which comparatively rejected better ethanol, proved to be less relevant in the context of dealcoholisation.…”