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[Clean up] What to do with aq. Layer after Extraction?

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Brennendes Wasser

Brennendes Wasser

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Senior member Chemical engineer
Hello!

So there are a lot of ideas how to make an Extraction more eco friendly.

Switching from Lye to other stuff and re-using the Naphtha of course.




But for me I have another question as

- I just dilute any Lye and toss it into the drainage

- I let the Naphtha fully evaporate instead of doing anything different with it



but what to do with the aqueous Layer, after you have fully extracted it?

So I proceed with the Naphtha layer (which will evaporate), but I still got that aqueous, which does not contain any goodies anymore.

Now one may say: Well ... then just toss it into the drainage too ?!

But when I put my nose closely to this, I can definetly still smell some Naphtha.

Probably because there is still are very very tiny amount which will never fully separate, so this aqueous solution still got Naphtha in it (but I do not know to what extent).

And as Naphtha is toxic for water organisms and overall not wanted in the sewage / waste water, I would feel uncomfortable to toss it into the drainage too.



What do YOU do with the aq. Layer?
 
I read here that evaporating naphtha is harmful for the environment and should be avoided but if you have no problem with it and evaporate all your naphtha then leave the container open, all the residual naphtha will evap eventually, then into the drain
 
I neutralize the soup with vinegar and toss the whole mess into the compost pile. I don’t worry about residual naphtha, I believe that microbes in the compost are plentiful enough to withstand the bits of it that end up there. I imagine most of it is evaporated before long anyways.

-Lover
 
With most acids and bases, "dilution is the solution". The ions in the water will sooner or later find their counterparts and neutralize.

I don't have much soup since I do A/B extraction with filtration and use separatory funnel to get last bits of naphtha out.

So I throw the bark in the trash and there is only about 1.6 l of basic soup.

I neutralize the soup with HCl (as it reacts with lye, forming a mere table salt, rendering the soup completely harmless) and boil it for some minutes to boil off any residual naphtha. Then I pour it down the drain.

As for the naphtha itself, I distill it off instead of evaporating (to concentrate the extract for faster crystallization). The naphtha poured from Pyrex dish so the is put in a metal container labeled "USED NAPHTHA" - when I have lots of it, I perform backsalting to recover any DMT left there, then re-distill for reuse.

I still lose quite a bit due to evaporation, but this can hardly be prevented.
 
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