Sodium acetate and water

ticklemylemon

hi,

i'm just wondering if there is a way to extract sodium acetate from water? the obvious one would be to evaporate water.. but that would be way too expensive on alarge scale. I was thinking maybe using some kind of extractant? But because these components are both soluble in water i'm not sure how to go about it.

Any ideas?

locum-motion

Water is H2O.
It has neither Sodium ions nor Acetate ions in it.
So: No; it is impossible to extract Sodium Acetate from water.

On the other hand, it would be possible to extract Sodium Acetate from an aqueous solution of Sodium Acetate. I suspect that that's the question you actually intended to ask.

As to the answer to that question, I'm afraid I'm not that kind of chemist. Someone else might be able to answer.

ticklemylemon

Yes, I have a solution that is a mixture of water and sodium acetate and im trying to separate them + trying to avoid evaporation route.

mawk

Why avoid the evaporation route? Works fine for several industries. Lithium mining for example evaporates whole lakes.

Otherwise, reverse osmosis and scrape the SA off the membrane?

Woodward

You could try drastically lowering the pH and try to separate it into an organic solvent

ticklemylemon

Woodward wrote: »

You could try drastically lowering the pH and try to separate it into an organic solvent

can you elaborate on that please?

Woodward

ticklemylemon wrote: »

can you elaborate on that please?

The pKa of a carboxylic acid is around 5 so at a pH below this the unionised form of the acid will prodominate. This will have a higher affinity for the organic layer than the ionised form so if you repeatedly extract an acidic solution of sodium acetate with an organic solvent you will get some of it in the organic solvent which you can then evaporate

ticklemylemon

What organic solvent would you recommend for me to use? Would toluene be ok?

Woodward

ticklemylemon wrote: »

What organic solvent would you recommend for me to use? Would toluene be ok?

Toluene would work but I would go with DCM. It is easier to evaporate afterwards and it forms the bottom layer which is more practical for an extraction

dirtyden

Just boil off the water. Tyring to extract sodium acetate from water with dichoromethane!

Do you realise you are trying to do something that wont work with a toxic solvent that will be soon be licensed for use, also requiring acid, it still wont work in any case.

Boil off the water, it is the most sensible option.

ticklemylemon

Tyring to extract sodium acetate from water with dichoromethane!

Difficulty I have is that sodium acetate is very soluble in water. If i add dichloromethane to a mixture of water and sodium acetate, I dont think CH3COONA will just go into the solvent layer, or will it?? :eek: (Would it not just sit in the water layer?)

Woodward

ticklemylemon wrote: »

Tyring to extract sodium acetate from water with dichoromethane!

Difficulty I have is that sodium acetate is very soluble in water. If i add dichloromethane to a mixture of water and sodium acetate, I dont think CH3COONA will just go into the solvent layer, or will it?? :eek: (Would it not just sit in the water layer?)

Thats why you lower the pH. It generates acetic acid (pKa about 5) which does not dissociate at a pH below 5 and is somewhat soluble in organic solvents. Every time you extract it you will get some going into the organic layer and by repeating this you will get acetic acid which you can then convert to sodium acetate when you are using it with sodium bicarb assuming you want to use it in solution

ticklemylemon

Ah I see. And is there a way to separate water from acid afte extraction???

dirtyden

Your problem here is acetic acid is soluble in water. It wont preferentially migrate to an organic solvent easily.

You are trying to overcomplicate this. Why would you extract to an organic solvent, which would only be done with great diffculty as what you have done is effectively dissolved an acid in acid, there is little driving force to get it into the organic solvent. You would need an immense amount of solvent which you still have to distill to remove.

Or you could just distill the water, rather than a three step process requiring gargantuan amounts of solvent for limited recovery, a pH adjustment and a distillation.

I dont understand how you feel extracting will be cheaper it would significantly add to the expense.

Woodward

dirtyden wrote: »

Your problem here is acetic acid is soluble in water. It wont preferentially migrate to an organic solvent easily.

You are trying to overcomplicate this. Why would you extract to an organic solvent, which would only be done with great diffculty as what you have done is effectively dissolved an acid in acid, there is little driving force to get it into the organic solvent. You would need an immense amount of solvent which you still have to distill to remove.

Or you could just distill the water, rather than a three step process requiring gargantuan amounts of solvent for limited recovery, a pH adjustment and a distillation.

I dont understand how you feel extracting will be cheaper it would significantly add to the expense.

I never said it would be cheaper or that it is the best way. The poster said they would rather avoid evaporation of water at all costs. I presented them with the only other alternative that doesnt involve chemically derivatising it

Adamcp898

Tbh OP, if you are indeed actually just separating sodium acetate in water, there is literally no reason why you shouldn't boil it so long as you are able to heat the water to 100 degrees safely i.e. own a suitable container and a hot plate.

However, if you are in fact trying to separate the sodium acetate from solution because you inadvertently added it when you shouldn't have, and you need to separate it because there is another compound in the solution that you actually need to keep and heating would degenerate it then just tell us what it is or at least what family/related compounds it comes from and someone will be able to help.

It's easier to separate things once we know what chemistry we're working with.

ticklemylemon

Woodward wrote: »

The pKa of a carboxylic acid is around 5 so at a pH below this the unionised form of the acid will prodominate. This will have a higher affinity for the organic layer than the ionised form so if you repeatedly extract an acidic solution of sodium acetate with an organic solvent you will get some of it in the organic solvent which you can then evaporate

What I did was i added HCl to sodium acetate(+water) and pH went down to ~2.3 and i proceeded to do extraction with DCM.

I tried testing the organic layer for acetic acid, however no test gave positive results for its presence

So i presume acetic acid is still stuck in aqueous layer... ? It would make sence as acids would much rather prefer water than organic solvents, so my question is why did you think it would go into organic solvent???

ticklemylemon

Adamcp898 wrote: »

Tbh OP, if you are indeed actually just separating sodium acetate in water, there is literally no reason why you shouldn't boil it so long as you are able to heat the water to 100 degrees safely i.e. own a suitable container and a hot plate.

However, if you are in fact trying to separate the sodium acetate from solution because you inadvertently added it when you shouldn't have, and you need to separate it because there is another compound in the solution that you actually need to keep and heating would degenerate it then just tell us what it is or at least what family/related compounds it comes from and someone will be able to help.

It's easier to separate things once we know what chemistry we're working with.

I'm actually working on a waste sample which contains water and sodium acetate and some other components(less than 4%), which im not really worried about.

I'm trying to reduce amt of waste leaving the plant so im looking at ways to reduce the the volume that is brought to incinerator.

dirtyden

Woodward wrote: »

I never said it would be cheaper or that it is the best way. The poster said they would rather avoid evaporation of water at all costs. I presented them with the only other alternative that doesnt involve chemically derivatising it

It simply wont work to any extent.

Osmosis or some kind of membrane filtration might work but boiling water is the cheapest way of doing it.

SOL

If all you are trying to do is reduce waste volume and there are no harmful volatile components in the waste stream evaporation would seem like the ideal way to do this. Can you leave the waste somewhere with good airflow for a while?

As you have discovered it is not going to be possible to extract acetic acid from water and I suspect that adding more things to your waste stream (such as HCl solution and DCM) is going to cost way more than any potential saving.

One other question, what is the other 4%? this is probably very important because if it were just a simple sodium acetate solution it would be possible to dispose of it in normal sewage...