Metastannic acid discovery?

[Xsvfan1]

I'm not sure if this was a one time thing or something that actually works.

Well I was doing a test batch on pins and it created the gray goo... so I set it off to the side to finish up some other stuff... well I threw a chunk of copper into to see what it would do... the next day all the metastannic acid was gone and only coated the chunk of copper with a black coating.

Does metastannic acid leach onto the copper and go back into a solid? Like if it's that easy to deal with I think it would be a miracle

 

[Xsvfan1]

I don't have any before pictures but it was mostly grey goo. That's what it looks like after pulling the copper chunk out

 

[Elemental]

I was looking for some more information on tin removal during processing and stumbled onto this research paper. It doesn't really answer your question specifically, but has some good insights. Enjoy

Article
Hydrometallurgical Process for Selective Metals
Recovery from Waste-Printed Circuit Boards

Authors: Željko Kamberovi´c , Milisav Ranitovi´c, Marija Kora´c, Zoran Andji´c, Nataša Gaji´c, Jovana Djoki´c and Sanja Jevti´c

Abstract: This paper presents an experimentally-proved hydrometallurgical process for selective
metals recovery from the waste-printed circuit boards (WPCBs) using a combination of conventional
and time-saving methods: leaching, cementation, precipitation, reduction and electrowinning.
According to the results obtained in the laboratory tests, 92.4% Cu, 98.5% Pb, 96.8% Ag and over 99%
Au could be selectively leached and recovered using mineral acids: sulfuric, nitric and aqua regia.
Problematic tin recovery was addressed with comprehensive theoretical and experimental work,
so 55.4% of Sn could be recovered through the novel physical method, which consists of two-step
phase separation. Based on the results, an integral hydrometallurgical route for selective base and
precious metals recovery though consecutive steps, (i) Cu, (ii) Sn, (iii) Pb and Ag, and (iv) Au,
was developed. The route was tested at scaled-up laboratory level, confirming feasibility of
the process and efficiencies of metals recovery. According to the obtained results, the proposed
hydrometallurgical route represents an innovative and promising method for selective metals
recovery from WPCBs, particularly applicable in small scale hydrometallurgical environments,
focused on medium and high grade WPCBs recycling.

Elemental

 

[Yggdrasil]

Hmm I will definitely read this.
Thanks for sharing Elemental.
Regards Per-Ove

 

[Geo]

Metastannic acid is not gray. It is white and has a light, fluffy appearance. It will stay suspended in solution for hours or even days depending on a few factors. The hydrated tin oxide can be colored from the solution it's in.
To completely remove the metastannic acid from trapped foils (the most common problem), drain and add distilled water well over the material allowing room for expansion of the reaction in your reaction vessel. Add sodium hydroxide until the PH is neutral. Drain all solution and allow the mass to dry completely . Drying on heat causes an adverse effect on the process. Desiccating is best. Once the mass is dry, add acetic acid (market brand will work) until all reaction stops. This creates stannous acetate. Add HCl slowly and in small increments until all of the stannous acetate is dissolved. Now you can filter the foils from the solution. You have effectively removed the tin from the gold.

 

[Lino1406]

No way tin will coat on copper, wise versa

 

[Xsvfan1]

I'm going to take pictures and show. I'm working on recreating it to see if it was a one time deal or not.

I had quite a bit of it in the bottom of a beaker due to multiple tests on variety of pins.
In the original container it looked like the copper had a dark black coating with a small black puddle next to it like it had melted. So I decanted the liquid to get down to the copper peice. I pushed it around in the bottom of beaker rather vigorously until it broke free and got cloudy. Acted exactly like other things I have cemented out

 

[DHarr]

Metastannic acid is not gray. It is white and has a light, fluffy appearance. It will stay suspended in solution for hours or even days depending on a few factors. The hydrated tin oxide can be colored from the solution it's in.
To completely remove the metastannic acid from trapped foils (the most common problem), drain and add distilled water well over the material allowing room for expansion of the reaction in your reaction vessel. Add sodium hydroxide until the PH is neutral. Drain all solution and allow the mass to dry completely . Drying on heat causes an adverse effect on the process. Desiccating is best. Once the mass is dry, add acetic acid (market brand will work) until all reaction stops. This creates stannous acetate. Add HCl slowly and in small increments until all of the stannous acetate is dissolved. Now you can filter the foils from the solution. You have effectively removed the tin from the gold.

I hope this saves my project. I have been racking my brain for weeks now and searching for recommendations on this that don't seem hard/messy and this seems genius if it works. Don't have to buy anything, don't have to use up more of the expensive acids, no special equipment needed. I am going to try a test tube batch next time I am in the lab and if it looks good I will give the full run the treatment. Good looking out Geo!

Attached is a good picture showing the complexity of the metastannic acid settling out.

 

[DHarr]

Once the mass is dry, add acetic acid (market brand will work) until all reaction stops. This creates stannous acetate. Add HCl slowly and in small increments until all of the stannous acetate is dissolved. Now you can filter the foils from the solution. You have effectively removed the tin from the gold.

I do have some question. When you say add acetic acid, how pure does it need to be? Are we talking vinegar, or some 99.85% food grade? Does it matter if it is glacial or not?

Thanks

 

[Geo]

I do have some question. When you say add acetic acid, how pure does it need to be? Are we talking vinegar, or some 99.85% food grade? Does it matter if it is glacial or not?

Thanks

No. It doesn't matter. Market brand clear vinegar will work well.

 

[Wonka]

Metastannic acid is not gray. It is white and has a light, fluffy appearance. It will stay suspended in solution for hours or even days depending on a few factors. The hydrated tin oxide can be colored from the solution it's in.
To completely remove the metastannic acid from trapped foils (the most common problem), drain and add distilled water well over the material allowing room for expansion of the reaction in your reaction vessel. Add sodium hydroxide until the PH is neutral. Drain all solution and allow the mass to dry completely . Drying on heat causes an adverse effect on the process. Desiccating is best. Once the mass is dry, add acetic acid (market brand will work) until all reaction stops. This creates stannous acetate. Add HCl slowly and in small increments until all of the stannous acetate is dissolved. Now you can filter the foils from the solution. You have effectively removed the tin from the gold.

Will this work for gold powder aswell?

 

[Yggdrasil]

Will this work for gold powder aswell?

It only affects the MetaStannic acid, not the foils or powder, why do you ask.

 

[Wonka]

It only affects the MetaStannic acid, not the foils or powder, why do you ask.

I have a bunch of it, and think there might be gold powder trapped in it.

 

[Wonka]

I have a bunch of it, and think there might be gold powder trapped in it.

Also, like an idiot. I thought is was silver chloride at first and added it to my silver chloride bucket. Is there any good trick to separate the two?

 

[Wonka]

Also, like an idiot. I thought is was silver chloride at first and added it to my silver chloride bucket. Is there any good trick to separate the two?

You can clearly see the separation line between the two. I thought about just trying to suck the top layer off.

 

[Yggdrasil]

You can clearly see the separation line between the two. I thought about just trying to suck the top layer off.

Well if it is indeed Silver Chloride and MetaStannic acid.
Silver Chloride will not react at all with Acetic acid.
Mind you, I have not tried nor tested with Acetic acid.
But if it works, what will be left, are Silver Chloride and other insolubles.

 

[Thomas M Joseph]

Metastannic acid is not gray. It is white and has a light, fluffy appearance. It will stay suspended in solution for hours or even days depending on a few factors. The hydrated tin oxide can be colored from the solution it's in.
To completely remove the metastannic acid from trapped foils (the most common problem), drain and add distilled water well over the material allowing room for expansion of the reaction in your reaction vessel. Add sodium hydroxide until the PH is neutral. Drain all solution and allow the mass to dry completely . Drying on heat causes an adverse effect on the process. Desiccating is best. Once the mass is dry, add acetic acid (market brand will reactionork) until all reaction stops. This creates stannous acetate. Add HCl slowly and in small increments until all of the stannous acetate is dissolved. Now you can filter the foils from the solution. You have effectively removed the tin from the gold.

Dear Geo, could you further explain these reactions so that I may explore the chemistry involved. First, the reaction of metastannic acid and sodium hydroxide and secondly, that product(sodium stannate?) and acetic acid. Thank you.

 

[Yggdrasil]

Dear Geo, could you further explain these reactions so that I may explore the chemistry involved. First, the reaction of metastannic acid and sodium hydroxide and secondly, that product(sodium stannate?) and acetic acid. Thank you.

He says nothing about Sodium Stannate. He says neutralize the solution which means bring to pH 7.
Then dry it and add Acetic acid.
Sodium Stannate forms when you dissolve the Tin with Sodium Hydroxide.
When you add Acetic acid you form Stannous Acetate.
On can also dry it and roast it to a low ref glow and then dissolve the Tin Oxide with HCl.

 

[Thomas M Joseph]

Dear Yggdrasil, you misunderstand my question. I was assuming that the reaction of metastannic acid and sodium hydroxide produced sodium stannate. Then the addition of acetic acid produced stannous acetate. Correct me if this is wrong. Balanced equations would help me...especcially for the stannous acetate. Thanks for your input.

 

[Yggdrasil]

Dear Yggdrasil, you misunderstand my question. I was assuming that the reaction of metastannic acid and sodium hydroxide produced sodium stannate. Then the addition of acetic acid produced stannous acetate. Correct me if this is wrong. Balanced equations would help me...especcially for the stannous acetate. Thanks for your input.

Unless he push the pH past 7, he would just convert the HCl to NaCl and water.
HCl + NaOH gives NaCl and H₂O

Then he dries it and add acetic acid which dissolves the Meta Stannic Acid H₂O₃Sn
by creating Tin Acetate, which is soluble in HCl.

If you roast it after the neutralization you will create a mess by melting the NaCl.

On the other hand if you roast it without adding NaOH you will convert the
Meta Stannic Acid H₂O₃Sn to SnO2 which also is soluble with HCl.

Anyway the easiest is to not make Meta Stannic Acid in the first place.