CIELO - Washing used solvent after storing a few years

[shroombee]

I have some unwashed ethyl acetate (used for CIELO extractions) stored in their original plastic bottles. One bottle contains used solvent from extractions over three years ago, and the second bottle contains solvent from extractions over one year ago. The used solvent now smells like ethyl acetate mixed with a little vinegar. Would there be complications trying to reclaim the solvent after such a long time?

I'm in the middle of washing some of the 3-year old solvent now. After 12 hours the solvent is clear, but the pH is exactly the same as the unwashed solvent. I adding another teaspoon of sodium carbonate and a teaspoon of water and will wait another 12 hours.

 

[Loveall]

You can test the pH strips on new EA, make sure it looks neutral. Since pH strips are designed mostly for water, neutral point may look a little different depending on brand of pH strip.

Because you may have vinegar/ethanol after all this time in acidic conditions perhaps a few water washes will help remove all of that. The vinegar should convert to sodium acetate during neutralization and while don't know how soluble sodium acetate is in ethyl acetate, I imagine it is easy to move into the water. Ethanol may need more water washes to remove.

 

[shroombee]

Thanks for your response, Loveall. For my future processing runs on these old solvents, do you suggest water washes before or after doing the sodium carbonate steps?

What do your pH strips look like after reclaiming the solvent? For my orange paper pH strips, new EA shows basically no color change except a very faint red line at the edge of where I dipped the pH strip.

For the reclaimed solvent, after multiple additions of sodium carbonate and water, and decanting to new jars twice to begin new cycles, the pH strips still show a prominent red line at the edge of where the strip was dipped into the reclaimed solvent. They also have a faint greenish tint where the strip was fully dipped. The greenish tint matches the tint on a strip of pH paper dipped in purified water. I can't seem to get rid of the red line regardless of how many cycles I run and after many hours of mag stirring.

Note the pH strips for the unreclaimed, used solvent are very obviously red.

 

[Transform]

Bit of a footnote here, but I use just a small square torn off the pH strip and moisten it with a tiny bit of DIW before testing a drop of nonaqueous solvent using the corner of a (clean!) spatula or some fine tweezers to save on pipettes as well, what with being a massive tightwad and all.

This means the dipping of test papers into solvents or solutions can be avoided completely. (I'm clumsy and sometimes drop them in )

Looking at the pic a bit, I wonder if the red line is from ethanol turning the strip into a mini-chromatogram. The greenish colour of the strips seems to fade as more carbonate washes are performed, if I'm understanding your picture correctly.

I'd be tempted to test the ethanol hypothesis by adding a small, measured amount of it to a sample of the EA and testing it once more.

Thinking about the greenish response of the strips, perhaps it can by lessened by drying the EA with something like anhydrous SC or even just a brine wash.

 

[Loveall]

Wow, so detailed.

I do remember seeing that red line and simply proceeded after the bulk of the pH strip was neutral (I'll add the info about the red line to the TEK). Sorry that I didn't mention it!

 

[shroombee]

Bit of a footnote here, but I use just a small square torn off the pH strip and moisten it with a tiny bit of DIW before testing a drop of nonaqueous solvent using the corner of a (clean!) spatula or some fine tweezers to save on pipettes as well, what with being a massive tightwad and all.

This means the dipping of test papers into solvents or solutions can be avoided completely. (I'm clumsy and sometimes drop them in )

Looking at the pic a bit, I wonder if the red line is from ethanol turning the strip into a mini-chromatogram. The greenish colour of the strips seems to fade as more carbonate washes are performed, if I'm understanding your picture correctly.

I'd be tempted to test the ethanol hypothesis by adding a small, measured amount of it to a sample of the EA and testing it once more.

Thinking about the greenish response of the strips, perhaps it can by lessened by drying the EA with something like anhydrous SC or even just a brine wash.

Interesting... I'll test the ethanol hypothesis and also try drying the reclaimed EA. Currently, the TEK finishes by adding water so the sodium carbonate clumps, and there is a water layer between the SC and the EA.

Wow, so detailed.

I do remember seeing that red line and simply proceeded after the bulk of the pH strip was neutral (I'll add the info about the red line to the TEK). Sorry that I didn't mention it!

Okay, so your results imply I successfully reclaimed the EA, even though it sat around with dissolved citric acid for a few years. I'll someday do a test extraction with this reclaimed solvent versus new EA to prove it is still effective.

 

[shroombee]

I was able to mostly get rid of the red line by washing the reclaimed solvent with water. There is still a very faint red line which matches the faint red line from the pH strip tested on new, unused ethyl acetate.

For the final step, I added a tablespoon of sodium carbonate to dry the reclaimed solvent. After mag stirring for an hour, then letting it rest overnight, I poured the solvent through a coffee filter. The solvent has a faint cloudiness and there are very fine particles of (presumably) sodium carbonate at the bottom of the jar. Which of these options is best:

1) Add excess sodium carbonate to dry the solvent, in which case there will be traces of sodium carbonate in the solvent which were not caught by the coffee filter;
2) Add excess water and decant so the solvent will be clear and there will be no traces of sodium carbonate. In this case, the ethyl acetate will likely be saturated with water.

The TEK seems to imply option #2 is best, as the last step is to add excess water until the solvent is clear.

 

[doubledog]

I would expect that small particles should settle at the bottom with sufficient time. At least that is the method which worked for me in such cases ( but I do not work with EA).
Another option is filtering through some fine sand, bentonite, diatoma or similar material.

 

[Loveall]

I was able to mostly get rid of the red line by washing the reclaimed solvent with water. There is still a very faint red line which matches the faint red line from the pH strip tested on new, unused ethyl acetate.

For the final step, I added a tablespoon of sodium carbonate to dry the reclaimed solvent. After mag stirring for an hour, then letting it rest overnight, I poured the solvent through a coffee filter. The solvent has a faint cloudiness and there are very fine particles of (presumably) sodium carbonate at the bottom of the jar. Which of these options is best:

1) Add excess sodium carbonate to dry the solvent, in which case there will be traces of sodium carbonate in the solvent which were not caught by the coffee filter;
2) Add excess water and decant so the solvent will be clear and there will be no traces of sodium carbonate. In this case, the ethyl acetate will likely be saturated with water.

The TEK seems to imply option #2 is best, as the last step is to add excess water until the solvent is clear.

I think you mean traces of sodium citrate?

#2 is what I do, but doesn't need to be excess water. It can be a few drops of water until the fine un filterable sodium carbonate quickly clumps up into larger filterable chunks.

Also, to more quickly remove all the citric acid next time, a little bit more water added with sodium carbate also works. It's not dissimilar from crashing mescaline citrate - some water is needed to form a hydrated salt. In the early neutralization bubble stage you can see a boost in bubble production after adding a teaspoon of water.

Or, wait and use a finer filter system to catch the finer sodium citrate that forms under slower drier conditions like doubledog mentions.

 

[shroombee]

I would expect that small particles should settle at the bottom with sufficient time. At least that is the method which worked for me in such cases ( but I do not work with EA).
Another option is filtering through some fine sand, bentonite, diatoma or similar material.

After waiting longer, the solvent is clear with a very light layer of (presumably) sodium carbonate at the bottom of the jar (probably a few mg).

I think you mean traces of sodium citrate?

Wouldn't it be traces of sodium carbonate that got through the coffee filter? All of the citric acid should have been neutralized after multiple cycles of adding sodium carbonate, water, decanting, repeating multiple times, etc. Recall that I ran the reclamation steps many times, trying to get rid of the red line on the pH paper, until washing with water finally turned out to be the key step.

#2 is what I do, but doesn't need to be excess water. It can be a few drops of water until the fine un filterable sodium carbonate quickly clumps up into larger filterable chunks.

I'll experiment with adding drops of water, as well as trying doubledog's suggestion of filtering through bentonite.

Also, to more quickly remove all the citric acid next time, a little bit more water added with sodium carbate also works. It's not dissimilar from crashing mescaline citrate - some water is needed to form a hydrated salt. In the early neutralization bubble stage you can see a boost in bubble production after adding a teaspoon of water.

Or, wait and use a finer filter system to catch the finer sodium citrate that forms under slower drier conditions like doubledog mentions.

The TEK says to add one teaspoon of sodium carbonate plus one teaspoon of water for each teaspoon of citric acid used during salting. For faster citric acid removal, are you suggesting a little more water (such as an extra 1/2 teaspoon of water), or a little more water plus a little more sodium carbonate (for example 1.5 tsp of sodium carbonate and 1.5 tsp of water)?

 

[Loveall]

Yes, more water helps speed the neutralization reaction.

It seems your EA was very dry for some reason.

Excess water will also clump up fine particles of sodium carbonate.

I think your issues (slow neutralization and hard to remove fine sodium carbonate) happened because you were low on water for some reason.