# Electrowinning instead of cooper cementing



## amesametrita (Oct 26, 2012)

What do dear forum members think about using electrowinning instead of cooper cementing from AgNO3 before refining cell?


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## butcher (Oct 26, 2012)

I do not see a benefit, cementing with copper is so fast and easy and does a great job, 

If electrowinning the silver, the cell if a graphite anode was used it would also push copper and most any other metal involved out of the solution with the silver, besides adding graphite carbon to the solution and the silver would be more contaminated with copper, giving you more copper in your silver than you would have if the silver was cemented out of solution using copper.


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## amesametrita (Oct 27, 2012)

butcher said:


> I do not see a benefit, cementing with copper is so fast and easy and does a great job,
> 
> If electrowinning the silver, the cell if a graphite anode was used it would also push copper and most any other metal involved out of the solution with the silver, besides adding graphite carbon to the solution and the silver would be more contaminated with copper, giving you more copper in your silver than you would have if the silver was cemented out of solution using copper.



One forum member posted a simple and clever design:

http://www.goldrefiningforum.com/phpBB3/viewtopic.php?t=13614

With cementation you loose Cu and nitric.
With electrowinning you can even reuse recovered nitric for digestion and cement with Cu well contaminated solution only.
Am I right?


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## goldsilverpro (Oct 27, 2012)

> What do dear forum members think about using electrowinning instead of cooper cementing from AgNO3 before refining cell?



The man with the cylindrical cell had Ag or Au cyanide solutions and you have a silver nitrate solution. Big difference.

I assume you have dissolved silver and a contaminant, most likely copper, in nitric acid and now you want to plate out all of the silver from this solution onto a cathode, using an inert anode such as carbon. Then you want to remove the silver from the cathode, melt it into bars, and purify it in a silver cell. Then you want to reuse the nitric. Is that all correct?

A possible scenario. In a silver/copper nitrate solution, depending on the ratio of the 2 metals, silver will tend to plate out first. When the silver is depleted to a certain level, copper will start co-depositing with the silver. With further plating, the percentage of copper in the deposit will be greater and greater. When all the silver has been deposited, all of the copper will also have been deposited. The end result will be that all of the silver and copper that you originally dissolved will be combined in the deposit and you will be back to square one.

Another possibility. At an inert anode, the current splits water into oxygen gas (which escapes) and hydrogen ion, H+ (which enters the solution). As the silver/copper deposits, the NO3- released will combine with the H+, producing nitric acid, HNO3. As the nitric builds up, it will, at some point, start dissolving the silver/copper that has been deposited. The result is that the total amount of metal deposited will tend to be limited. If there was unused nitric in the solution to start with, this condition would be worse.

A third. As the metals in the solution are depleted, the deposition at the cathode becomes less efficient and the current applied there starts splitting water. The lower the metal content, the more the water splitting. The result is that you will probably never be able to plate out 100% of the metal.

What actually happens will most likely be a combination of all of these things. In other words, what you want to do won't work, at least with decent efficiency. Cement the silver with copper - the silver will be 98-99% pure and you'll get all of it quickly. If you weren't heavy handed with the nitric, a pound of copper can cement 3.4 pounds of silver. Even if you paid $5/pound for copper, that's only $0.10 per oz of silver.


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## HAuCl4 (Oct 27, 2012)

Lazersteve has a thread about this exact topic including a discussion of the original patent and how he implemented it. I saved the link in another computer, but it should not be too difficult to find with a search.


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## amesametrita (Oct 27, 2012)

While I'm searching for Lazersteve post let me clarify the idea:
Step by step.
1) Digest Ag In nitric (inquartation in my case)
2) Run through series of cylindrical cells. In the end of the series the return pipe contains a long basket with granulated silver which redigest in released nitric.
3) As soon as liquid becomes too contaminated make normal copper cementation (much less copper involved).
4) Cemented and electrowinned goes through conventional cell.


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## goldsilverpro (Oct 27, 2012)

Good luck. To me, you are way over complicating the situation. If you want to just play around, that's one thing. If you want to make money, you keep it simple and fast. Both the cementation and the silver chloride method meet those requirements if you do them properly.


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## butcher (Oct 27, 2012)

Cement silver from AgNO3 with copper metal, the copper can be recovered from the weak nitrate solution using the graphite anode, copper powder can be reused, dilute nitric could also be reused for some processes, this Idea Laser Steve, He made some posts on this method.


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## goldsilverpro (Oct 27, 2012)

I think this is the thread of Steve's you're looking for. It's a sticky in the silver category
http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=50&t=2868

Here's the patent
http://www.google.com/patents/US4033838?dq=patent:4033838&hl=en&sa=X&ei=t2aMULf8MMS02wXWm4GIBA&ved=0CDEQ6AEwAA


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## butcher (Oct 27, 2012)

This gives me a chance to tell every one how much I appreciated the information GSP has provided on the forum concerning silver and gold recovery and refining, and also how much I like his book, which for me was money well spent.




http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=84&t=5810


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## goldsilverpro (Oct 27, 2012)

Thank you, Richard! Actually, I think you were the first person to buy my book (remember the hassle? I do.) and, for that, I will always ingratiate you. Who knew at the time that you were going to be a most important moderator?


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## Marcel (Nov 1, 2012)

I hope it is still within the topic, but I have a problem that has to do with the great ability of copper to precipitate Ag from Ag nitrate. I have a large number of silverplated copperwire.
If I would apply nitric to them, would that be a full process? I tested a few wires and I found that once I remove them from solution, the silver gets dissolved again (sorry I have littel experience with nitric). What would be the solution? Adding NaOH before removal until the ph does not allow the nitric to further dissolve any silver? Dilute the nitric to minimal?
What is the best way to avoid redisolving silverplated copperwire after imm. precipitation? And is the precipitation most likely complete? I also added a solid piece of copper. But each time I removed all solids the silver vanished into solution again.


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## goldsilverpro (Nov 1, 2012)

Use only enough nitric to dissolve the copper/silver. The only way I can see the cemented silver redissolving is that you used too much nitric and ended up with an excess.


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## Marcel (Nov 1, 2012)

Would - the other way around - adding more material to the solution solve the problem as well?


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## butcher (Nov 1, 2012)

Why would you have a whole pile of copper wires with some silver on them, sounds like you need a large buss bar, re-use the same copper wire until you have no more copper metal left, and find a thick buss bar.


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## nickvc (Nov 2, 2012)

Marcel if your silver plated copper wire has a very low silver yield it's probably not economically viable to recover it using nitric which is fairly expensive. Do you know the silver percentage in the wire?
If it is very low then my suggestion would be to melt the wire into bars and use them when you need to cement silver nitrate solutions, this is a win win situation as you recover the silver in solution and also the silver in the bars made from your wire so you get that silver back virtually for free.


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## Marcel (Nov 2, 2012)

@nickvc: That sounds clever to me. I will try that ! But I rather leave them as wires, so they have a larger surface for reaction.


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## butcher (Nov 2, 2012)

Some times I will use copper wire for cementing silver from silver nitrate, I like to use the very thin wire from unwinding transformers, I will take a some of this wire coiled around my fingers and lightly twist it together, hold the end with a pair of needle nose pliers over a light torch flame to burn off the varnish tap it to try and break off ash much ash as possible, wash it off with my garden hose, and put it into my silver nitrate solution a small roll at a time, with stirring well and crushing the copper plated silver now and then, before all of the silver is out of solution I will go to a larger thick bar of copper so I do not have small pieces of undissolved copper wire in the powdered silver, with this I do end up with a little ash from the varnish on the copper wire, but it has not been a problem, this silver is used in in-quartering gold so if a very small amount of copper wire was left It is not a problem (although I have not seen any sign of it as the copper wire is so fine it seems to easily be replaced by silver in the acidic solution).


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