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Metallus
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[*] posted on 17-7-2019 at 02:28
Chemistry of insoluble sulfides


Whereas the oxides and halogenides of transition metals have a rich aqueous chemistry, the corresponding sulfides are among the most water insoluble compounds (Eg CuS, Ag2S, HgS) and represent a dead end.

What are the typical approaches to extract transition metal compounds (oxides, chlorides, etc) from the corresponding sulfides that do not involve sulfide roasting? Is there any viable aqueous routes (eg acid digestion or redox reactions, or complex formation with chelant or even alkaline fusion) or these compounds are just for disposal?

For example, Ag2S can be reduced with Al in aqueous solution using baking soda as electrolyte (home method to remove tarnish from silverware).

If you have specific book chapters or papers or other threads/references involving this type of chemistry, they are very welcome.

Thanks

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fusso
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[*] posted on 17-7-2019 at 02:31


Oxidise with nitric. It works with CuS.

[Edited on 190717 by fusso]




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teodor
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[*] posted on 17-7-2019 at 02:45


I think that any good old book designated to the topic of cations analysis contains a plenty of information on this topic. Check Treadwell and Vogel. All systematic methods are based on precipitation of metals as sulfides and then getting them into solution again.


So,

Treadwell, Analytical chemistry, Vol 1, 2. (There are several editions and sometimes they are completely different in approach - my personal opinion is that the latest one is not the best).


Vogel, Textbook of Macro and Semimicro Qualitative inorganic analysis. Mostly based on the methods of Treadwell and his co-workers, this book nevertheless contains some very interesting remarks about underlying chemistry (also chemistry of sulfides). The last editions were reworked and the most interesting parts were thrown away, so use edition <= 5.

So, Ag2S is (according to Treadwell) is easily soluble in hot dilute nitric acid and HgS is dissolved by colourless (i.e., without polysulfides) sodium sulphide (according to Vogel).


[Edited on 17-7-2019 by teodor]
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yobbo II
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[*] posted on 17-7-2019 at 14:33



They will dissolve in molten NaOH. (danger)
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Bedlasky
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[*] posted on 17-7-2019 at 22:16


Ag2S should be soluble in Na2S2O3.

CuS is soluble in ammonia.

HgS maybe in thiourea or KI (I'd have to make a calculation but I haven't time just now).
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[*] posted on 18-7-2019 at 00:38


For example oxidative leaching. If you take chalcopyrite CuFeS2 and put it in hydrochloric acid, the kinetics of leaching copper is really slow. If you however combine it with persulfate or hydrogen peroxide you will be able to decompose it. So basically we are talking here about hydrometallurgy.



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Metallus
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[*] posted on 18-7-2019 at 01:05


Thank you guys, you gave me really nice answers.

@teodor thank you very much for the references. I'm currently reading Vogel's one and it contains a lot of reactions back to back with the systematic study of each cation/anion. Very easy and informative. I'll check Treadwell's one later, but so far I'm very satisfied with the info I got.

@Hegi yes, I also found that hydrometallurgy contains a lot of practical information on how to deal with metal sulphides, but many textbooks on it (such as "Hydrometallury in extraction processes" by Gupta) are very expensive or hard to find.

Keep the answers coming though, if you have more to add :)
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teodor
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[*] posted on 18-7-2019 at 04:22


Quote: Originally posted by Metallus  

@teodor thank you very much for the references. I'm currently reading Vogel's one and it contains a lot of reactions back to back with the systematic study of each cation/anion. Very easy and informative. I'll check Treadwell's one later, but so far I'm very satisfied with the info I got.


You are welcome. In case you will discover something interesting doing experiments with sulfides just create a topic here - I also work with them (now doing experiments with SnS2), so, we will be able to discuss.

It's also interesting that H2S (sulfides) method is only one practical method of systematic cations analysis. There were efforts to develop another methods but they were not widely accepted. So, probably the chemistry of metal sulfides is really unusual .
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[*] posted on 19-7-2019 at 05:21


Quote: Originally posted by Bedlasky  
Ag2S should be soluble in Na2S2O3.

CuS is soluble in ammonia.

HgS maybe in thiourea or KI (I'd have to make a calculation but I haven't time just now).

Regarding CuS, I assume you mean NH3 solution on water, right? And which products are formed? [Cu(NH3)4]2+ and S2-?
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yobbo II
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[*] posted on 19-7-2019 at 13:03



For some books (if you don't already know).

https://libgen.is/

Try chemistry of sulphides
also chemistry of sulfides
also sulphides
sulfides
etc

[Edited on 19-7-2019 by yobbo II]
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[*] posted on 20-7-2019 at 03:50


I thought I would throw some light on removing sulfides with no roasting using a non-traditional approach that may be of interest for inorganic and organic sulfides. Interestingly, lab light appears to produce remarkable decomposing ability on some sulfides, some of which that appear to be seemingly impervious to even pure oxygen treatment alone (hence the use of a combined O2/light protocol).

See, for example, commentary on Cadmium sulfide under lab light at https://books.google.com/books?id=GClzU2-Rj18C&pg=PA487&... with reports in some labs of 50% to 90% decomposition! The effect of the light is described as 'immediate' and 'variable'.

So, with the aid of UVC light, an acid of your choice and an air pump, I would propose a photolysis reaction system (see ‘Highly efficient method for oxidation of dissolved hydrogen sulfide in water, utilizing a combination of UVC light and dissolved oxygen’ by Yizhak Tzvi and Yaron Paz, in Journal of Photochemistry and Photobiology A: Chemistry, Volume 372, 1 March 2019, Pages 63-70, at https://www.sciencedirect.com/science/article/pii/S101060301... , in particular, Equations (1) to (10)).

To quote from the referenced source:

“Results were explained by the following mechanism:
HS− + O2 --Light--> HS• + •O2− (1)
HS• + O2 → HO2• + S (2)
HS• + •O2−→ HO2− +S (3)
HS− + (x−1)S → H+ +Sx2− (4)
where x can be 2-5.
Sx2− +S ⇌ Sx + S2− (5)
Sx2− + 1.5O2 → SO32− + (x−1)S (6)
Sx2− + 1.5O2 → S2O32− + (x−2)S (7)
S2O32− ⇌ S + SO32− (8)
SO32− + 0.5O2 → SO42− (9)
S2O32−+ 2.5O2 → 2SO42− (10)
Once polysulfide is formed, it readily reacts with oxygen, yielding thiosulfate (reaction 7) and sulfite (reaction 6). The elemental sulfur formed in reactions 2 Experimental, 3 Results is consumed by the growing polysulfide chain (reactions 4, 5). This ensures that under the right conditions, HS− is constantly consumed without releasing of elemental sulfur. The thiosulfate and sulfite are further oxidized to give sulfate, the final product (reactions 9, 10). “

Also, of possible interest, see 'Efficient Metal‐Free Aerobic Photooxidation of Sulfides to Sulfoxides Mediated by a Vitamin B2 Derivative and Visible Light' by
Tomáš Neveselý Eva Svobodová Josef Chudoba Marek Sikorski Radek Cibulka,2016. https://onlinelibrary.wiley.com/doi/pdf/10.1002/adsc.2015011... .

To quote part of the abstract:

"process for the aerobic photooxygenation of sulfides to sulfoxides mediated by riboflavin tetraacetate or riboflavin (vitamin B2) photocatalysts and visible light (450 nm) in an acetonitrile‐water (85:15 v/v) mixture. The optimised solvent system leads to both singlet‐oxygen and electron‐transfer pathways in photooxygenation, thus allowing oxidation of electron‐poor and electron‐rich thioanisoles, dialkyl sulfides and sterically hindered sulfides. Besides having a broad substrate scope, the method has very short reaction times and requires low catalyst loading (down to 0.1 mol%). These properties are due to the high photocatalyst stability and the extremely high quantum yields..."
--------------------------------------

Interestingly, once sulfite is created, some recycling of radicals to the system in the presence of light may be possible. To cite a source (https://pubs.acs.org/doi/abs/10.1021/ja00756a009 ):

SO3(2-) + hv --> •SO3- + e- (+ O2 --> •O2- )

[Edited on 20-7-2019 by AJKOER]
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Bedlasky
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[*] posted on 20-7-2019 at 11:28


Quote: Originally posted by Bezaleel  
Quote: Originally posted by Bedlasky  
Ag2S should be soluble in Na2S2O3.

CuS is soluble in ammonia.

HgS maybe in thiourea or KI (I'd have to make a calculation but I haven't time just now).

Regarding CuS, I assume you mean NH3 solution on water, right? And which products are formed? [Cu(NH3)4]2+ and S2-?


Yes.
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[*] posted on 20-7-2019 at 17:21


Quote: Originally posted by Bedlasky  
Quote: Originally posted by Bezaleel  
Quote: Originally posted by Bedlasky  
Ag2S should be soluble in Na2S2O3.

CuS is soluble in ammonia.

HgS maybe in thiourea or KI (I'd have to make a calculation but I haven't time just now).

Regarding CuS, I assume you mean NH3 solution on water, right? And which products are formed? [Cu(NH3)4]2+ and S2-?


Yes.


Sure about the S(2-) anion?

Some research claim that it is practically non-existent in solution! See, for example, 'Call to erase aqueous sulfide ion from chemistry - Spectroscopic developments question the existence of aqueous sulfide ions', by Alexandra Heaffey, February 2018 at https://www.chemistryworld.com/news/call-to-erase-aqueous-su... .

Perhaps a cuprous salt, like [Cu(NH3)2H2O)4]HS ?

Reference on the cuprous ammonium complex, see https://onlinelibrary.wiley.com/doi/abs/10.1002/bbpc.1963067... .

[Edited on 21-7-2019 by AJKOER]
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[*] posted on 21-7-2019 at 08:50


You will not get suphide ion forming in aqueous solution. It's too strong of a base.

The reaction is CuS + 4 NH3 + H2O = [Cu(NH3)4](2+) + OH- + HS-

However, the equilibrium constant for that is about 10^-24, so I'm skeptical of the claim that copper(II) sulphide will dissolve in ammonia. Hydrogen sulphide is often used to strip copper out of stable complexes.




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[*] posted on 23-7-2019 at 05:32


Quote: Originally posted by Metallus  
Thank you guys, you gave me really nice answers.

@teodor thank you very much for the references. I'm currently reading Vogel's one and it contains a lot of reactions back to back with the systematic study of each cation/anion. Very easy and informative. I'll check Treadwell's one later, but so far I'm very satisfied with the info I got.

@Hegi yes, I also found that hydrometallurgy contains a lot of practical information on how to deal with metal sulphides, but many textbooks on it (such as "Hydrometallury in extraction processes" by Gupta) are very expensive or hard to find.

Keep the answers coming though, if you have more to add :)


I think you can find many papers on this topic available on the internet. For example I did this transformation of stibnite (Sb2S3) into water soluble complex by reacting it with sodium sulfide and NaOH. It yieldid this Na3SbS4 yellowish crystalline solid.




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