Very small concentrations can usually be separated by liquid/liquid extraction with multiple stages. The difficulty will be to find a solvent that takes up the ethanol but is not miscible with water. Secondly the solvent has to be food grade since you cannot be sure that the water will be totally immiscible with the solvent.

have you tried distillation? Distillation at the ethanol boiling point will allow ethanol to evaporate but how to collect the ethanol may be difficult in case you are interested with the ethanol otherwise you may allow the ethanol to evaporate in the atmosphere and get separated from water. Also note that the method will involve heat if you experiment is heat sensitive!

That is what i think.

I would also think that distillation should work as ethanol will evaporate

The use if rotary evaporator set at the temperature of the ethanol will make ethanol to evaporate first after some time

Thank you prof. Harald Schuchmann for your information.

Thanks Solomon Olum , Difo Voukang Harouna , Olusegun Abayomi Olalere . It doesnot work as ethanol concentration is very low.

The separation can be done via heating the alcoholic mixture. Generally alcohol boiling temperature is lower than that of water, it will become steam in a short time, then can be condensed into a separate container. You can also freeze the blended liquid (alcoholic mixture), which allows for partial removal of the nonalcoholic components; what remains will be richer in alcohol.

Ethanol can be separated from water through distillation/evaporation, irrespective of the concentration, due to different boiling points. Similarly, separation can be done using solvent extraction or membranes. However, most of the separation processes are regulated by equilibrium constraints, so you will always end up with poor removal rate/efficiency at low concentrations. Low concentration and poor separation also means you will face issues in analyzing ethanol concentration. If something doesn't work (membrane in this case), it could also mean your analytical methods are not appropriate. You should share more details: ethanol concentration, analysis method etc. .

Progressive freeze-concentration is a technology to separate water from solutions by freezing. In our experience, the freeze concentration of ethanol-water solutions is possible. In the present investigation, ethanol-water solutions were freeze-concentrated by the progressive stirred technique. The ethanol concentration was found to have increased by 1.3 and 2.1 times at the end of the freeze concentration process. . This technique proved to be valid with respect to the concentration of ethanol-water solutions, with better yields being obtained at low initial concentrations.

Eduard Hernandez

Is this technology, "Progressive freeze-concentration" based on change in the freezing point due to the presence of impurities ?

Progressive freeze-concentration is one type of Freeze Concentration (FC). FC is the removal of pure water in the form of ice crystals at subzero temperatures. FC process is based on the crystallization of water from the solution. Crystallization is highly selective in the removal of water. The process also operates at freezing temperatures and therefore is capable of maintaining the original composition balance and protecting heat sensitive components.

The FC process is dependent on two main characteristics of the concentrated products. The viscosity of the concentrate at its freezing point determines the maximum concentration obtainable by FC. The freezing point depression due to the solute concentration can be so great that the lower temperature límit for the refrigerant may be reached. This can be overcome by using specialty refrigerants and multistage refrigeration systems, but these are usually too expensive to be feasible.

For laboratory purposes, anhydrous ethanol is obtained by distillation with metallic sodium, or salts, which form a crystalline hydrate. The most affordable and cheap is copper sulphate. Its molecule binds 5 water molecules.

Even if the concentration of ethanol is low it can be separated by distillation.

you can try distillation.

dear Alaa El Din Mahmoud , when I have ethanol traces on my samples I add some acetone and then evaporate using a rotavapor until all the solvent evaporates.

best regards.

While aiming at the mentioned industrial separation of ethanol from dilute aqueous solutions, it seems mandatory to consider just techniques of a relatily low energy requirement. Distillation seems unsuitable, because a large amount of water would have to be vapourised along with ethanol, increasing the energy demand.

As you want to consider other approaches besides pervaporation, you may want to give some attention to the apparent possibility of selective gas stripping followed by condensation of the evaporated ethanol. Alternatively, you seemingly could consider solid-sate adsorption (column adsorption), by using some suitable ethanol-selective sorbent (e.g. silicalite), regenerated for its own recycling and ethanol recovery. Also liquid-liquid extraction of the aqueous ethanol by some convenient immiscible solvent (e.g. 4-decanol) could be considered.