-1
$\begingroup$

I want to remove phenol from wastewater so I used the cyanex923 as an extractant or carrier to extract phenol from the wastewater (the name of the process is non-dispersive solvent extraction) but the problem is that I don't know what to do at the last step when the complex cyanex923-phenol is formed. I know that I need a stripping step to separate these two components and when I googled, I see some people said that NaOH can be used and some people said NaCl but I don't know exactly how it works, like what happens when NaOH or NaCl is added, please can anyone help me to explain the process because I'm totally lost

$\endgroup$
7
  • 2
    $\begingroup$ Wouild help if you told us what cyanex923 is, and what it dissolves in $\endgroup$ – Waylander May 24 '19 at 12:34
  • $\begingroup$ I want to remove phenol from wastewater so I used the cyanex923 as an extractant or carrier to extract phenol from the wastewater but the problem is that I don't know what to do at the last step when the complex cyanex923-phenol is formed. I know that I need a stripping step to separate these two components and when I googled, I see many people said that NaOH can be used but I don't know exactly how it works, like what happens when NaOH is added, please help me $\endgroup$ – Park Chimchim May 24 '19 at 14:38
  • $\begingroup$ Phenol is acidic enough that it will form the water soluble sodium salt when treated with NaOH $\endgroup$ – Waylander May 24 '19 at 14:40
  • $\begingroup$ So you mean that when NaOH is added to the complex cyanex923-phenol, water soluble sodium salt will form? Can you please explain a bit more? I'm not good at chemistry $\endgroup$ – Park Chimchim May 24 '19 at 15:02
  • $\begingroup$ Phenol is really pretty acidic with a pKa 10, so any basic solution over pH11 or stronger will completely form the sodium salt. Dissolve your complex up in a water-immiscible solvent (see my answer below) and wash that solution with aqueous sodium hydroxide $\endgroup$ – Waylander May 24 '19 at 15:12
3
$\begingroup$

So far as I can see from Google, Cyanex 923 is a liquid mixture of trialkyl phosphine oxides. This should be soluble in the standard range of organic solvents (ethyl acetate, diethyl ether, methyl t-butyl ether) so washing a solution of the cyanex923-phenol complex with aqueous sodium hydroxide will remove phenol without the cyanex going into aqueous. Usual drying, filtration and solvent evaporation under reduced pressure will give the cleaned cyanex

$\endgroup$
2
$\begingroup$

Based on the original question, I can only speculate if further detail about the composition of cyanex923 may be helpful for the OP, or not.

On the other hand, there is at least one scientific publication about this complexant's compositon by a Polish group deploying GC-MS. (Sounds like determining the secret of WD40.) To paraphrase the publication, 18 peaks were identified, four of them about these major components: trihexylphosphine oxide (8.5%), octyldihexylphosphine oxide (30.4%), dioctylhexylphosphine oxide (37.4%), and trioctylphosphine oxide (16.1%) summing up to 92.4%, and mostly n-alkyl groups.

Beside cyanex923, sibling formulations cyanex925, 921 and Topo -- at time of the study all tradenames of products by then American Cyanamide Company (defunct since 1994) are equally surveyed.

Reference: Dziwinski and Szymanowski in Solvent Extraction and Ion Exchange, 16, 1998, 1515-1525, doi 10.1080/07366299808934592 at Taylor & Francis (or here at ResearchGate).

Addition

  • There is an open-access publication by the same group about properties of cyanex923, including the determination of extraction isotherms for various phenols between water and octane or toluene like depicted in the following figure (unsubstituted phenol is described by the squares):

enter image description here

(reference: Polish Journal of Chemical Technology, 12, 2010, 19-23, doi 10.2478/v10026-010-0027-9)

  • Still by same group, the extraction performance of cyanex923 deployed in membrane extractors was compared with amberlite and trioctylamine in hollow fiber modules. Cyanex923 performed much better than the other two, as for example depicted in the following figure:

enter image description here

(reference: Environmental Science & Technology, 36, 2002, 2088-2093, doi 10.1021/es010910w)

$\endgroup$
1
$\begingroup$

After I've done some researches I think it works like the following:

We need an extraction module and a stripping module. The organic stream in the extraction module containing the phenol–cyanex complex is sent to the stripping module. The complex diffuses across the microporous wall filled with organic solution to the stripping–organic interface and I think in the stripping module we have NaOH which reacting to the phenol and form PhONa (sodium phenolate) (according to the article, this step occurs in a hollow fibre membrane contactor and I wonder why can't we just use a tank?).

This means that at the interface cyanex is regenerated and recycled back to the extraction module. The solute (sodium phenolate) is then released into the aqueous stripping solution. I'm not sure what they mean by "the aqueous solution" but anyway, we have the PhONa and need to be converted back to the phenol so that we can use phenol again and I think we can do it in acidification condition.

Some study researches mentioned that we can add HCl to lower pH and when the the pH drops the phenol associates and forms an organic phase separated from a saline aqueous phase.

This is what I've understood from some articles that I've read, please correct me if I'm wrong

$\endgroup$
1
  • $\begingroup$ Among the papers around the original one co-authored Szymanowski, there are at least two potentially relevant to your question. Have a look at them. $\endgroup$ – Buttonwood May 26 '19 at 14:39

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.