Can ethanol be purified by reverse osmosis?

Dave - I don't want to comment on the legality of this so let's stick to the science!

What is reverse osmosis in the first place? This is used quite often for purifying water, to get salt out of it. Essentially, you have a membrane, which will let water through but not salt, for example.

So, if you apply pressure to the side with the salt water, the water molecules are forced through the membrane but the salt can't get through. So you end up with more salty water on one side, and fresh water on the other side.

Essentially, what the questionner is attempting to do is get a membrane which will let water through but not alcohol; then apply pressure to it, and that pumps the water out leaving a stronger solution of the alcohol behind (and all the other stuff in there).

I imagine it would end up tasting very, very strong, because very few of the taste molecules are going to get through so it's going to end up with a very, very flavoursome brew.

I also think it depends on the membrane. I've looked up that some membranes are better at this than others. You'd have to pick one which is particularly good at noticing a difference between the alcohol and the water. And if you get one which works, if you pick the right membrane, there's no reason why it wouldn't work...