Recovery of Zinc from Impure Silver Brick

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yoyo282

Member
Joined
Jan 25, 2023
Messages
8
Location
India
Hi all,

I have 30 kg of impure silver brick which has roughly 60 % silver 25% copper and 15% zinc. I am able to purify silver by nitic acid treatment followed by displacement reaction with copper, and I am able to recover copper using iron, however, I am struggling to separate zinc. Is there a way to separate zinc from the solution? I don't really want to use metallic-reducing agents to do it as this leads to a never-ending chain of reactions.

Any help will be really appreciated.

Thanks!
 
yoyo282 said:
Hi all,

I have 30 kg of impure silver brick which has roughly 60 % silver 25% copper and 15% zinc. I am able to purify silver by nitic acid treatment followed by displacement reaction with copper, and I am able to recover copper using iron, however, I am struggling to separate zinc. Is there a way to separate zinc from the solution? I don't really want to use metallic-reducing agents to do it as this leads to a never-ending chain of reactions.

Any help will be really appreciated.

Thanks!
Click to expand...
If you really want to, you can precipitate it as zinc hydroxide by adding sodium hydroxide solution slowly to the acidic waste until no more precipitate forms and the pH is between 5 and 7. Don't add it to excess, otherwise the zinc hydroxide will begin to dissolve again as the solution turns basic. Zinc hydroxide is practically insoluble in neutral or slightly acidic aqueous solutions.

You could also drop it as zinc carbonate.by treating the acid with calcium carbonate. ZnCO3 is only marginally soluble, about 1mg/L in water.

Be aware that the carbonate reaction will foam a LOT with the release of CO2 gas. The hydroxide reaction is much less messy, you just need to watch that the pH doesn't get too high.

Both zinc hydroxide and carbonate are white solids.
 
My only question is why?
The value you could possibly recover is not worth the effort , if you have environmental worries just use the section here for disposing safely of your wastes. We like to be consistent in pushing our members to be responsible in disposing safely of any waste they produce, this sounds like a university question to new students.
You can convert the zinc by making the solution more basic but I fear that is not the answer you want or need.
 
Hi,
I remember one person who was attempting to get pure silver from transition silver coins that were newer than the "old English standard Sterling" but still had a high silver content, If he did not remove the zinc he had problems pouring nice castings of anything out of the silver he recovered.
This culd be one reason Why, without making someone admit they are melting old coin which can be illegal in many different countries
 
AustAuScrap said:
Hi,
I remember one person who was attempting to get pure silver from transition silver coins that were newer than the "old English standard Sterling" but still had a high silver content, If he did not remove the zinc he had problems pouring nice castings of anything out of the silver he recovered.
This culd be one reason Why, without making someone admit they are melting old coin which can be illegal in many different countries
Click to expand...
According to himself he is trying to reclaim the Zinc.
The Silver and Copper he has control of.
 
Most smelters cook off the metallic Zinc to Zinc oxide, at around 850C. - 950C. The ZO is captured in a bag house, then converted back to metal separately. You don't want to do this indoors, and if outdoors, do not breath the fumes. It is then much easier to deal with the 2 metals appropriately.
 
goldshark said:
Most smelters cook off the metallic Zinc to Zinc oxide, at around 850C. - 950C. The ZO is captured in a bag house, then converted back to metal separately. You don't want to do this indoors, and if outdoors, do not breath the fumes. It is then much easier to deal with the 2 metals appropriately.
Click to expand...
I agree, Zinc fever is not something I consider as comfortable ;)
:cool:
 
Once you cemented copper out, you have iron in solution, this will also come out at a lower pH by adding soda or lye.
Try to raise pH slowly, filtering in between the steps of adding lye as soon as hydroxides form. They have different colors. You might be able to find a point where all iron is converted into hydroxides and a big part of the zinc is still in solution. There will be a pH level where both are insoluble.
Then it's a matter of smelting with a reducing flame and flux like carbon. Or redissolving with HCl and cementing back out on more reactive metal, if that works.
Lots of work for a small profit? Maybe yes, maybe no...
 
Hi,
apologies for my mistake/misunderstanding the question..
Good thing I pay more attention to detail and consequently safety in my actual operations.
Certainly in my processing I don't bother with anything worth less than copper, from a pure economics point of view. without even considering the actual risk you have mentioned.
 
I'm a bit confused. Am I right that you have ingots of silver, copper, and zinc - ingots - not presently dissoloved in nitric acid? You want to produce refined silver - starting from the ingot - right?
 
jobinyt said:
I'm a bit confused. Am I right that you have ingots of silver, copper, and zinc - ingots - not presently dissoloved in nitric acid? You want to produce refined silver - starting from the ingot - right?
Click to expand...
Hi,

Yes, I have an ingot that primarily contains silver, copper, and zinc. Extracting silver and copper is fairly straightforward however zinc is not. Are there any ion exchange/chromatography methods / electrolysis methods you guys are aware of for the extraction of zinc?

Alternatively, I will resort to making some zinc compound that sells well.( Any leads on this? )

Thank you for all the help!
 
yoyo282 said:
Hi,

Yes, I have an ingot that primarily contains silver, copper, and zinc. Extracting silver and copper is fairly straightforward however zinc is not. Are there any ion exchange/chromatography methods / electrolysis methods you guys are aware of for the extraction of zinc?

Alternatively, I will resort to making some zinc compound that sells well.( Any leads on this? )

Thank you for all the help!
Click to expand...
How many kilos of this ingot do you have?
 
yoyo282 said:
Hi,

Yes, I have an ingot that primarily contains silver, copper, and zinc. Extracting silver and copper is fairly straightforward however zinc is not. Are there any ion exchange/chromatography methods / electrolysis methods you guys are aware of for the extraction of zinc?

Alternatively, I will resort to making some zinc compound that sells well.( Any leads on this? )

Thank you for all the help!
Click to expand...
Well I don't know how much resources you are willing to spend for 4.5 Kg of Zinc, it is less than 15 USD in value minus the process and labor.
I'd let it go.
Reclaim the Silver and Copper and treat the rest as waste.
 
As a learning experience as this isn't economically viable at this scale. You could extract the zinc either with an acidic process based on sulfuric acid or a basic process using lye, both with an electrowinning step at the end to recover the metallic zinc.

A rough sketch of the processes...
1. Sulfuric acid : Recover silver by cementing on copper. Recover copper by cementing on zinc. Now you have a zinc nitrate solution. Add enough sulfuric acid (an excess isn't damaging) and distil off nitric acid leaving a solution of sulfuric acid and zinc sulfate. Electrowinning the zinc with a pure zinc cathode and a platinum anode. You get the sulfuric acid back and metallic zinc.
2. Lye : After you have recovered the copper, add lye to precipitate all metals but continue until zinc is redissolved, check the pH. Filter off the zincate solution. Electrowin the zinc on a nickel cathode and a platinum anode. The result is a very fine zinc powder that can catch fire if allowed to dry out... don't ask me how I know that, but I caught it in time. :)

Nurdrage on youtube have two very good videos on how to electrowin zinc from solution. Watch them for more details.

As this is a lot of equipment as well as a lot of work for little gain I only recommend these processes for learning about chemistry, but it might come in handy if you want to recover some of the nitric acid or have a hard time to get pure zinc. The sulfuric acid in the acidic process is recovered and can be used many times.

/Göran
 
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