# Galvanic Copper reduction with formaldehyde and NaOH



## Atto (May 29, 2015)

Hello everybody!

I work to a company that receives alot of galvanic waste. They press filter it then ship to germany, there they recover the copper and nickel in the "galvanic mud".

We are trying to do this process here to reduce costs, what is usually done is to add sodium hydroxide and formaldehyde to reduce it to copper and nickel metal.

We are having some trouble with the reduction, we add more formaldehyde than it's needed (because of this reaction auto-catalytic nature) and when filtering the solution still contains dissolved copper.

The copper and nickel waste is precipitated in the galvanic process with calcium oxide.

Anybody have experience with this process? Do you have a literature to indicate?

Thanks!


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## Lino1406 (Jun 4, 2015)

While optimal pH for Ni is 8, for Cu is probably
lower. Work in 2 stages: 1)Optimize pH for Cu
2)Precipitate Ni


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## Lou (Jun 5, 2015)

No.

Just take to pH 10.5. That'll get all of it. What doesn't come out is chelates so dose with hypochlorite until amine or sulfamate is oxidized.


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## Atto (Jun 14, 2015)

Lino1406:

With excess formaldehyde we could get the the copper and nickel, but it was an insane amount! Because of that I don't think the pH will modify the reduction of copper!


Lou:

We tried a small batch (~1kg), one that wasn't precipitated with calcium oxide, using 12% sodium hypochlorite and it worked wonderfully! Thank you!

but in another batch with the mud (precipitated with calcium oxide, the one I mentioned before) we didn't suceeded. I think we didn't add enought NaClO. 

Do you have any literature on how to titrate the amount of oxidizing amine and/or sulfamates? There's another way to measure other than titration?

I think that the pH must be at minimum 10.5 to work, higher pH's, like 13~14 should not interfere with the process, am I right?

I did not forget the platinum plated titanium anode, that you helped me! We suceeded in annealing with 100% hydrogen we will try with 100% argon, I will post on that topic, once I've had everything.


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## Lou (Jun 18, 2015)

Glad to know my advice helped you.

http://scholar.lib.vt.edu/theses/available/etd-042299-143911/unrestricted/thesis4.pdf

http://www.faqs.org/patents/app/20110280779
If it's not just the chelated waste water, but also the mud, you must account for the oxidation of those hydroxides of the metals to a higher oxidation state.

The product of the OCl- oxidation is usually black nickel (III) hydroxide, and copper (II) hydroxide. Hope this saved you money.

I'd forget the formaldehyde. 

Lou


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## Atto (Jun 20, 2015)

Thank you Lou! 

I will read it all as soon I have time! We are running some tests to find with the "hard way" the quantity of hypochlorite.

I searched for the best way to reduce these metal to the metallic state, and at the time, we decided to try the formaldehyde, because of it's price and availability.

Why wouldn't you use formaldehyde?
What would you use instead?


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## solar_plasma (Jun 21, 2015)

Lou said:


> http://www.faqs.org/patents/app/20110280779
> 
> 
> Lou



[0017] 2NH4++3NaClO→N2+3NaCl+3H2O+2H+

Would this be a way to make HCl (by distilling) for those who have easier access to NH4Cl and NaClO or Ca(ClO)2 than to HCl?

Wouldn't any produced HCl interact with unreacted ClO- and form chlorine?

If so, wouldn't this mix of compounds dissolve gold just like any other HCl/Cl-kindred method?


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## butcher (Jun 21, 2015)

Reactions of ammonia, ammonium compounds, and chlorine, or chlorites, can produce dangerous gases, and even possible explosive mixes, with or without metals in solution.

Not something you would want to be mixing without a very good understanding of the many different reactions that can take place in different circumstances.


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## solar_plasma (Jun 21, 2015)

Thanks butcher!


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## Atto (Jul 9, 2015)

> Glad to know my advice helped you.
> 
> http://scholar.lib.vt.edu/theses/availa ... hesis4.pdf
> 
> ...



Lou, why you would forget the formaldehyde?
What would you use instead? Hydrazine?

This Mud is the wash water from many plating baths (like copper, nickel, silver) that are concentrated, the cyanide oxidized and finally precipitated with either sodium hydroxide or calcium oxide.

Thanks!


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## Lou (Jul 9, 2015)

Hydrogen.


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## Atto (Jul 9, 2015)

> Hydrogen.



Because of it's price?

How would you do it? Just bubble it in the solution with the mud and sodium hydroxide?

Do you think of another alternative?

Thanks!!!!


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