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Author: Subject: Questions about piranha solution.
CycloRook
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[*] posted on 9-12-2021 at 11:49
Questions about piranha solution.


I have watched several videos on this mixture. I have some questions.

Does this solution destroy all organic molecules ?

To what degree does this solution destroy organic molecules ?

What is the mechanism of action on organic molecules ?

If you put a sample of aspirin or Tylenol into piranha solution what would happen ?

I would like to know how all this works but can't find any mechanism of action online.

Thanks
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B(a)P
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[*] posted on 9-12-2021 at 12:29


This is a bit simplistic, but not a bad start.
Piranha solution
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CycloRook
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[*] posted on 9-12-2021 at 16:12


Yeah. It seems like there solution wasn't as concentrated as some videos I've seen. I doubt the berry would have lasted longer.
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macckone
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[*] posted on 9-12-2021 at 20:10


There are a bunch of reactions going on, one is dehydration of organics with OH groups,
Another is addition of sulfate groups in place of other groups.
Then there is persulfate which is one of the most potent oxidizers known.
It will oxidize pretty much anything, including carbon.

answering the other questions

does this destroy all organic molecules? I haven't found any that it doesn't with the exception of fluorocarbons and things like carbon tetrachloride.

To what degree does this solution destroy organic molecules? To CO2 and H2O and what ever hetero atom oxides, with the exception of fluorocarbon groups and some chlorine compounds like phosgene and carbon tetrachloride.

Mechanism was already discussed. It is oxidation, like fire.

Paracetamol and acetyl salicylic acid will be completely oxidized.
With paracetamol, there is a nitrogen, It will leave as either nitrogen or form nitrosylsulfuric acid.
With nitrosylsulfuric acid being an oxidizer in its own right.

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CycloRook
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[*] posted on 27-12-2021 at 11:26


I just had a thought. Can piranha solution used to recover precious metals like platinum palladium or gold ?
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Tsjerk
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[*] posted on 27-12-2021 at 11:32


Quote: Originally posted by cycloknight19  
I just had a thought. Can piranha solution used to recover precious metals like platinum palladium or gold ?


From what?
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arkoma
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[*] posted on 27-12-2021 at 13:19


Quote: Originally posted by cycloknight19  
I just had a thought. Can piranha solution used to recover precious metals like platinum palladium or gold ?
HCl + clorox work pretty well




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CycloRook
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[*] posted on 27-12-2021 at 18:52


Quote: Originally posted by Tsjerk  
Quote: Originally posted by cycloknight19  
I just had a thought. Can piranha solution used to recover precious metals like platinum palladium or gold ?


From what?
anything I guess. Catalytic converters or anything that's an organic mix
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Bedlasky
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[*] posted on 27-12-2021 at 19:28


Catalytic converter isn't organic mix. It's mixture of various oxides and precious metals (Pt, Pd, Rh). And I personally never heard about organic mixture containing precious metals.

And to your question - no, piranha solution isn't suitable for extracting precious metals. For extraction of Pt, Pd and Au you need presence of chlorides, Rh and Ir can't be recovered by aqueous methods (Rh can be dissolved in molten NaHSO4, Ir in molten hydroxide with some strong oxidizer like KNO3 or Na2O2) and Ru and Os cannot be dissolved in acids, but they are attacked by highly oxidizing alkaline solutions or melts (NaClO etc.).

If you are interested in precious metals recovery, read something about industrial process of separation of precious metals.




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CycloRook
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[*] posted on 27-12-2021 at 22:05


I really need to do more reading on this. My thought was that piranha solution would essentially oxidize everything except the precious metals. Thanks
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Dr.Bob
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[*] posted on 28-12-2021 at 10:27


I have tried Piranha solution for some frits and other very dirty glassware, and it works on somethings, but not on everything, some frits it barely cleans at all. But they are dirty from a wide variety of things, and I don't know which ones are dirty with what, which makes things harder.
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macckone
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[*] posted on 31-12-2021 at 08:28


piranha is good for organics.
It is bad for inorganics as a lot of oxides and sulfates are insoluble.

For inorganics peracetic acid is my go to followed by nitric and aqua regia.
Obviously aqua regia can't be used on lead or silver contamination.
Those need straight nitric.

Peracetic acid is basically glacial acetic with 30% hydrogen peroxide.
It will convert most things to the acetates.
It is very good with insoluble hydroxides and carbonates.

Nitric acid will work on a lot of stuff and aqua regia will work on the rest.

Some insoluble oxides require chloric or perchloric acid (chrome oxide)
If you have sulfates stuck in a frit things get more complicated.
calcium sulfate requires soaking and drying to work it out of the frit.
barium sulfate, good luck with that. Don't use a frit for barium sulfate.

Na-EDTA can be used to dissolve really stubborn stuff.

Good paper on cleaning frits from back in the days before computer aided analysis (GC/MS, OES-ICP, etc).

https://pubs.acs.org/doi/pdf/10.1021/ac60044a602

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unionised
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[*] posted on 31-12-2021 at 16:58


Quote: Originally posted by macckone  

Peracetic acid is basically glacial acetic with 30% hydrogen peroxide.




No it isn't.
For a start, it smells different.
Also it's capable of oxidising manganese salts to permanganate.

The real problem with trying to use peroxides to get precious metals into solution is that they typically catalyse the decomposition of the peroxide before it has a chance to do any oxidising..
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macckone
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[*] posted on 4-1-2022 at 00:20


Unionised,

peracetic acid really is glacial acetic acid with hydrogen peroxide.
That is one of two methods for making it.

Notice I specifically mentioned using it with carbonates and hydroxides.
precious metals are better handled with nitric or aqua regia depending on the metal.
But gold and silver work with peracetic acid, numerous videos available on the process.
I don't work with platinum very often, I don't have that kind of money.

You really need to know what is on the frit before cleaning it.
If you don't then the order peracetic acid, nitric, aqua regia will work for all but the sulfates and water will work on a number of those.

Na-EDTA will work on sulfates according to the linked paper but a frit clogged with sulfates might be a total loss.
Lead and calcium can be slowly worked out with water, but barium sulfate is very stubborn.
It depends on how clean you need it and how much time you have.

Another trick is soaking with sodium bicarbonate, then hitting the frit with acetic acid.
You can get a small mount of sulfate to convert to carbonate and then the carbonate to acetate since these are equilibrium reactions.
But these take time.
It may be cheaper to buy a new fritted funnel if you factor in the time cost, the reagents are generally cheap.

Back to your manganese to permanganate, permanganate is pretty soluble while manganese oxide is not.
Peracetic acid has removed manganese oxide from glass for me.
Patent where manganese oxide is removed from denim with peracetic acid which leaves the blue dye in place:
https://patents.google.com/patent/WO1992013987A1/en

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Triflic Acid
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[*] posted on 4-1-2022 at 08:38


Manganese oxides also react with hydrochloric acid but produce Cl2 gas, so this must be done outdoors or in a well-ventilated area. This is how I clean my manganese-oxide-covered glass, by adding some HCl and then letting it sit in a plastic box with liquid hydroxide drain cleaner at the bottom outdoors for a couple of days. It removes the stains pretty well, and there is practically no chlorine smell.



Hope is not a reagent
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macckone
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[*] posted on 5-1-2022 at 11:45


Quote: Originally posted by Triflic Acid  
Manganese oxides also react with hydrochloric acid but produce Cl2 gas, so this must be done outdoors or in a well-ventilated area. This is how I clean my manganese-oxide-covered glass, by adding some HCl and then letting it sit in a plastic box with liquid hydroxide drain cleaner at the bottom outdoors for a couple of days. It removes the stains pretty well, and there is practically no chlorine smell.

Peracetic acid is really better for this one.
It is very fast and no Cl2 gas.
Just good old oxygen and manganese acetate.

Sulfuric acid is also good for manganese oxide.
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