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j_sum1
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[*] posted on 28-7-2016 at 03:02
Selenium sulfide and selenium extraction


I was going to post this in the short questions thread but I think it deserves its own thread -- that is if it has an answer at all.

I noted recently an anti-dandruff shampoo -- that it contained 1% selenium disulfide. I knew that there was some selenium in there but never imagined that it was that much. For a 1L bottle that means that there is probably about 5.5 grams of elemental selenium in there; which is a reasonable lump.

So it got me wondering if there was some way of isolating the selenium sulfide from the unholy mix that is a modern shampoo. I note that SeS2 is something of an approximation and that the actual chemical is a mixture of 8-atom rings of the form SenS8-n and a mixture of isomers with an average ratio of 1:2.

Wikipedia tells me that it is soluble in ammonium monosulfide -- whatever that is. (NH4)2S I assume. But that is unstable and decomposes before melting. I cannot imagine it functioning as a solvent and so I assume that the statement is one of those inaccuracies that wikipedia is famous for. But maybe there is a solvent that is at least partially selective for the selenium compound.

So, is there a way of separating the SeS2 or a selenium compound or even elemental Se from shampoo?


Let me say at the outset that I doubt that shampoo would be a useful or economic source of Se. But the idea presents a challenge to me and I was unsure whether it would be feasible at all and unsure where to start.




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[*] posted on 28-7-2016 at 04:32


Isn't ammonium sulfide the compound used in stink bombs? Maybe it's soluble because of the free hydrogen sufide it releases.
While I cant find info about selenium disulfide solubility, selenium hexasulfide appears to be soluble in carbon disulfide. Not sure if SeS2 is also soluble.




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[*] posted on 28-7-2016 at 06:20


Well, you'd think that it would be soluble in CS2. Sulfur is, and selenium disulfide would have the same structure as octasulfur, except with selenium taking the place of some of the sulfurs.



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[*] posted on 28-7-2016 at 16:43


I probably should not post new threads late at night. Thoughts are clearer this morning.

CS2 I think will be problematic. It dissolves so much that is non-polar. I would expect adding it to a shampoo would be inviting all sorts of mess and I doubt the separation would be that good. Not to mention the quantity (and cost) of the CS2 needed to process a litre of shampoo.

So, perhaps hot xylene? Working on the notion that SenS8-n isomers will behave similarly to S8, I would expect solubility in xylene but probably a bit less soluble. And sulfur in xylene has a very useful steep solubility curve that is good for crystallisation.

That then leads to the following suggested procedure:

  • Dessicate the shampoo to get rid of as much moisture as possible. This will likely lead to a thick goo or paste. But a powder would be nice.
  • Dissolve as much as possible in hot xylene -- hopefully extracting the selenium compound into the solvent.
  • Filter hot to remove the crud. (I expect this to be difficult. Gravity filtration will be too slow and likely to become clogged with polymeric goo. OTOH, I can see it clogging up a fritted glass too. Might have to be a buschner with paper.)
  • Slowly cool to allow the SeS2 to crystallise. I would expect crystals to be very fine. There are a lot of different isomers involved and large regular crystals seem unlikely.
  • Filter and recrystallise.

By now I would expect the smell to be a bit whiffy. This might not be a wonderful process. The idea is there though. At this stage I think I will leave it as a thought experiment. Anything wrong with what I have suggested so far???




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[*] posted on 28-7-2016 at 17:03


You could also possibly take your boiled down "shampoo extract" and strip off most non-polar things with a solvent like chloroform or maybe even just acetone. From there, CS2 or hot xylene would be much more selective.



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[*] posted on 29-7-2016 at 05:33


SexSy ... do you have a trouble with aliens?
Evolution 2001 Movie :D;):P:)




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[*] posted on 29-7-2016 at 05:46


Quote: Originally posted by zts16  
You could also possibly take your boiled down "shampoo extract" and strip off most non-polar things with a solvent like chloroform or maybe even just acetone. From there, CS2 or hot xylene would be much more selective.

Chloroform or aceton are not stricto senso a-polar and so they may dissolve also polar things. Better use benzene, toluene, CCl4, CS2, C2Cl4 ...

The main problem also is that into the shampoo mix, you have amphipilic molecules very happy to dissolve in both polar and apolar media following a micellar process (polar head inside, apolar queue outside ... or reverse apolar head inside and polar queue outside).

The best idea to me would be to red heat burn the dried shampoo goo with air flow and allow the fumes to pass into a captation solution or collumn.
In principle into the fumes CO2, H2O and the most interesting part H2S, H2Se, SO2, SO3, SeO2 and SeO3.




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[*] posted on 29-7-2016 at 06:22


What about


  • boil to dryness
  • roast the residue to destroy organics


then one or more of


  • extract w/CS2?
  • treat w/pirhana to further destroy carbonaceous residues?
  • treat w/HCl to reduce the Se?
  • treat with chlorine and sublime off the selenium chlorides?


these are the first things that come to my mind, as a person with no familiarity with Selenium chemistry




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[*] posted on 29-7-2016 at 06:41


Quote: Originally posted by PHILOU Zrealone  
Quote: Originally posted by zts16  
You could also possibly take your boiled down "shampoo extract" and strip off most non-polar things with a solvent like chloroform or maybe even just acetone. From there, CS2 or hot xylene would be much more selective.

Chloroform or aceton are not stricto senso a-polar and so they may dissolve also polar things. Better use benzene, toluene, CCl4, CS2, C2Cl4 ...

The main problem also is that into the shampoo mix, you have amphipilic molecules very happy to dissolve in both polar and apolar media following a micellar process (polar head inside, apolar queue outside ... or reverse apolar head inside and polar queue outside).
That wouldn't be a problem. The acetone or chloroform washes would be discarded regardless of what they contain. The point was that they would not dissolve the selenium sulfide.



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[*] posted on 29-7-2016 at 16:08


Quote: Originally posted by PHILOU Zrealone  
SexSy ... do you have a trouble with aliens?
Evolution 2001 Movie :D;):P:)

I did think of that reference too. Your humour is better than mine.


Re roasting -- to destroy organics - I don't have any confidence that the target compound won't simply go up in smoke. I think I'll avoid this.
Ditto pirahna. I think it likely that it will oxidise the SeS2 along with the carbon compounds with no practical gain.
Bubbling Cl2 gas through seems like an interesting idea. Of course that would result in SCl2 and S2Cl2 being formed -- along with the chlorination of whatever else is in the shampoo. I sense extraction issues.
Solvent selection... My thoughts were to select a non-polar solvent that would dissolve the selenium compounds selectively rather than a polar solvent that would dissolve much of the other junk. The problem is always going to be the surfactants that will interact with both, and also the emulsifiers that prevent separation.


Is there a good test for selenium that can be used to indicate where it is? It would not be much fun to go through a complex extraction process only to discover the selenium is still in with the junk to be discarded.

I stress that this is a thought experiment at this stage. There are easier ways to get Se. And I am led to believe that any Se chemistry is a bit hard on the olfactory system.




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[*] posted on 29-7-2021 at 16:27


Revisiting this topic as I cannot find any reasonably priced selenium ($2/g is more than shampoo).

Selenium sulfide boils at about 112C.

But selenium sulfide is an emulsion in selsun blue (and other shampoos).
It should be possible to break the emulsion with calcium chloride which is notoriously brutal on soaps.
Centrifuging will cause the selenium sulfide to aggregate toward the bottom of the solution.
As users of selsun blue will note, it aggregates into orangish yellow flakes if allowed to stand for a long time on a store shelf.
If you can remove the selenium sulfide from most of the solution, it should be possible to allow it to desiccate and then
heat to boil off the selenium sulfide.

I am sure there are other methods. But this seems the most reasonable at first glance.
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[*] posted on 29-7-2021 at 20:47


Quote: Originally posted by macckone  
Revisiting this topic as I cannot find any reasonably priced selenium ($2/g is more than shampoo)


Se 99,995% 25 g 5 EUR
https://chemcraft.su/product/23224

SeO2 99% 10 g 4 EUR
https://chemcraft.su/product/22044

H2SeO3 98% 10 g 1,77 EUR
https://chemcraft.su/product/22934

H2SeO4 pure, 80% in H2O, 50 g 14 EUR
https://chemcraft.su/product/22935

Na2SeO3 98% 10 g 1,48 EUR
https://chemcraft.su/product/21810

anyway the extraction from shampoo would be nice experiment




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[*] posted on 30-7-2021 at 00:30


Quote: Originally posted by macckone  

But selenium sulfide is an emulsion in selsun blue (and other shampoos).
It should be possible to break the emulsion with calcium chloride which is notoriously brutal on soaps.
Centrifuging will cause the selenium sulfide to aggregate toward the bottom of the solution.
As users of selsun blue will note, it aggregates into orangish yellow flakes if allowed to stand for a long time on a store shelf.


I sometimes get prescriptions for a cream / ointment that contains 4% SeS2
Never seen it aggregate into the tube even though I kept some for years.
It clearly has the color of SeS2 that I got from Onyxmet though (red-orange).
Next time pityriasis versicolor shows up I will be armed and will make the cream myself :)




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[*] posted on 30-7-2021 at 01:22


Interesting thread. Sulfur and selenium sulfide dissolve in solutions of sulfides, also in a solution of the so-called ammonium sulfide. Ammonium sulfide does not exist, it actually is ammonium hydrosulfide together with free ammonia in a 1 : 1 stoichiometric ratio, dissolved in water. In the past, such solutions were used in the lab quite a lot for analytic purposes (distinguising different metal ions, based on different precipitation-behavior with H2S, HS(-) and NH3/HS(-)).

Sulfide ion does not exist in water, but it does form in the solid state. In water, sulfide ion hydrolyses: S(2-) + H2O --> HS(-) + OH(-). This reaction is almost completely to the right, S(2-) is such a strong base that it is not present in water. Alkaline solutions, containing HS(-) dissolve selenium and selenium sulfide, giving nice red/brown solutions of polysulfide/selenium ions:

HS(-) + OH(-) + S --> S2(2-) + H2O
HS(-) + OH(-) + Se --> SSe(2-) + H2O

This reaction can continue:
S2(2-) + Se --> S2Se(2-)
SSe(2-) + Se --> SSe2(2-)
Even more selenium atoms and sulfur atoms can be absorbed. IIRC up to 5 atoms total of sulfur and selenium in the anions.

SeS2 behaves a lot like S, it indeed (as j_sum1 stated) is very similar to rings of S8, but with S-atoms replaced by Se-atoms in the rings and having average molar atomic ratios [S] : [Se] = 1 : 2.

I also have some SeS2 from Onyxmet and it is a fairly interesting compound, but elemental Se is more useful and of similar price.




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[*] posted on 31-7-2021 at 08:34


Fery,
Those are pretty good prices.
US customs is holding everything up.
My last russian shipment was sitting in chicago for 3 months.
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[*] posted on 31-7-2021 at 10:59


macckone, that's sad
my friend sold some reagents to MidLifeChemist into California, I suggested him to write that the parcel contains Polishing for optics samples or second choice Photographic materials, the field in the form at postal office was very small to fit there the first choice so he wrote there the second one. In my country both are custom free so custom officers do not check the parcel and immediately pass it further to be delivered by postal service. I expected that the same could be similar in USA, but was not sure, every country different customs. Maybe that helped. You know, when clerks have well filled document they are satisfied and do not care anymore.




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[*] posted on 3-8-2021 at 06:58


Fery,
The problem is they are just delayed, nothing to do with the inspection which they usually do not do.
They usually just stamp the paperwork and pass it on but it is taking months for that to happen.
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