February 22, 2024, 09:55:17 AM
Forum Rules: Read This Before Posting


Topic: Puzzling result: Liq. Liq. extraction using toluene  (Read 2511 times)

0 Members and 1 Guest are viewing this topic.

Offline curiouscat

  • Chemist
  • Sr. Member
  • *
  • Posts: 3006
  • Mole Snacks: +121/-35
Puzzling result: Liq. Liq. extraction using toluene
« on: February 11, 2015, 12:49:26 AM »
I'm trying to understand this observation: We had organics-contaminated-effluent-water with 3.5% organics (rest NaCl  16% & NaOH 1%). Extracted it with toluene & the organics extracted out poorly. Final organics content 3.3%.

Next, we treated original contaminated water with H2SO4 & re-extracted with toluene (pH~1). Magically organics are down to less than 1%.

Is this sort of behavior known? Does pH have a huge effect on extractibility of organics?

*Organics are being assayed using Chemical Oxygen Demand as a surrogate.

Offline discodermolide

  • Chemist
  • Sr. Member
  • *
  • Posts: 5038
  • Mole Snacks: +405/-70
  • Gender: Male
    • My research history
Re: Puzzling result: Liq. Liq. extraction using toluene
« Reply #1 on: February 11, 2015, 01:11:54 AM »
May be that some of the organics were present as the Na salt(s). Acidification re-protonated them and they extracted.
Development Chemists do it on Scale, Research Chemists just do it!
My Research History

Offline curiouscat

  • Chemist
  • Sr. Member
  • *
  • Posts: 3006
  • Mole Snacks: +121/-35
Re: Puzzling result: Liq. Liq. extraction using toluene
« Reply #2 on: February 11, 2015, 01:48:30 AM »
May be that some of the organics were present as the Na salt(s). Acidification re-protonated them and they extracted.

Interesting. Is there any easy way to test this hypothesis. Out of academic interest purely. To the process it doesn't matter. But deeper understanding never hurts. :)

Another motivation to know what's happening is that we are still stuck around 1% organics. Ideally we'd like to go lower than that.

Any tricks up your sleeve?

Offline discodermolide

  • Chemist
  • Sr. Member
  • *
  • Posts: 5038
  • Mole Snacks: +405/-70
  • Gender: Male
    • My research history
Re: Puzzling result: Liq. Liq. extraction using toluene
« Reply #3 on: February 11, 2015, 02:32:05 AM »
Well remembering some of the processes you have described here finding out what is going on may be difficult assuming the waste comes from them!
Give it two extractions or try extractions at a higher temperature.
Chlorinated solvents may be a better option, but that may be too expensive and may generate more waste than you are treating.
Development Chemists do it on Scale, Research Chemists just do it!
My Research History

Offline Arkcon

  • Retired Staff
  • Sr. Member
  • *
  • Posts: 7367
  • Mole Snacks: +533/-147
Re: Puzzling result: Liq. Liq. extraction using toluene
« Reply #4 on: February 11, 2015, 08:16:55 AM »
As I understand it, the partitioning coefficient will have to be determined experimentally.  So under controlled conditions, determine how much is extracted out of a defined (i.e. prepared in the lab) sample of contaminated water, or a certain volume into a certain volume of toluene.  Once you know that, it should scale, percentage-wise, with a real world sample of much great volume, proportionally.

That's a lot of caveats, but when you get to planning it out, you should see how it all fits.

N.B.  your treated effluent still has organic in it.  You've compensated for the toluene that has now dissolved in your treated effluent after extraction, right?
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline DrCMS

  • Chemist
  • Sr. Member
  • *
  • Posts: 1295
  • Mole Snacks: +210/-81
  • Gender: Male
Re: Puzzling result: Liq. Liq. extraction using toluene
« Reply #5 on: February 11, 2015, 09:16:28 AM »
From memory toluene has a solubility in water of ~0.05% which I think is about 50% more than the solubility of water in toluene.

Sponsored Links