# Recycling nitric acid from copper nitrate



## Mbosco0 (Feb 18, 2014)

Hello to all!!
This is my first post on this amazing forum full of great people and knowledge. I have been refining silver now from electrical contacts for a couple months now. I am using a very simple process to do so. I have just been dissolving the contacts in 50/50 solution of nitric then cementing the silver out with copper after the reaction has stopped. Now my question I have is how to recycle nitric acid from the left over copper nitrate. Now I know my solution of copper nitrate is most likely contaminated with other base metals. I was reading on the forum lazersteve talking about recycling nitric from copper nitrate via electrolysis. I was wondering if anyone can tell me how to do that. Creating a cell is not a problem. I have some knowledge in electrolysis due to my job as a toolmaker. Also is there a better way to recycle the nitric?? I was thinking of distillingbthe copper nitrate. Possibly setting up a distilation rig to heat up the copper nitrate and bubble the NOx gasses into distilled water or hydrogen peroxide. Once again I'm not 100% sure of this process. If anyone can help or comment that would be greatly appreciated. Thanks everyone.


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## bmgold2 (Feb 18, 2014)

I'm not sure if it works the same for nitrate as it does for sulfate but here's a video on making sulfuric acid from copper sulfate. He ended up using a platinum coated titanium electrode which isn't real cheap but if it worked to recover nitric acid from used solutions (which I don't know if it will), it might be worth buying one. You could probably try the carbon electrode and filter out the junk from the carbon rod just to test if the process might work. Sounds like a great idea if it worked.

[youtube]http://www.youtube.com/watch?v=5dUSF9Gl0xE[/youtube]


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## butcher (Feb 18, 2014)

Mbosco0,



It would not be easy to distill the copper nitrate solution to make a nitric acid, because copper nitrate crystallizes to a salt before it decomposes to gases.

Using electrolysis to deplete solution of the copper is a good method to reuse the copper solution.

But you still have a couple of options that will work.

The copper nitrate crystals can be heated, driving off NOx gas which can be bubbled into water (a bit of H2O2 to provide oxygen in solution) to form nitric acid and copper oxide powders.

Another option is to reuse the copper nitrate solution in a chemical reaction, dissolving metals (even more copper), and making nitric acid by distilling off the NOx gas and bubbling it into water and H2O2, at the same time you make a copper sulfate (which you can reuse in some other process or recover the copper and sulfuric acid...).
In the reaction the sulfuric acid takes the copper and with heat the nitrates decompose to NOx gases that can be distilled from solution to make nitric acid.
By adding sulfuric acid, and pieces of metal like copper (copper gold plated pins...) and then distilling off the NOx gases.

Killing two birds with one stone uses this option:
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=38&t=6199&hilit=killing+two+birds+one+stone


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## Mbosco0 (Feb 19, 2014)

Thanks for the response guys. I am definitely going to try the two birds one stone method. I will let you guys know my results.


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## Lou (Feb 19, 2014)

I think the most convenient way is to put it into a reactor, add sulfuric and distill the nitric acid for re-use. The copper sulfate can then be sold or cemented and sold as copper.

Kind of expensive though!


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## Mbosco0 (Feb 20, 2014)

Lou said:


> I think the most convenient way is to put it into a reactor, add sulfuric and distill the nitric acid for re-use. The copper sulfate can then be sold or cemented and sold as copper.
> 
> Kind of expensive though!



Hey Lou. Thanks for a response. Quick question. How much sulfuric are you adding to the solution. I understand that it all depends on the purity of the copper nitrate. Or do you just slowly add sulfuric to the solution until the reaction stops?


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## Lou (Feb 20, 2014)

I think it would be wise to know what you started with reagent-wise and where you're trying to go.

One mole sulfuric acid will give you two moles of nitric acid back from copper nitrate, at least theoretically. There will be some decomposition to NOx.


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## bmgold2 (Feb 20, 2014)

I was wondering around on this forum and found this topic. Processing Sterling Silver without nitric acid

http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=50&t=2868

Might be just what you are looking for. I think Lasersteve is making nitric acid from copper nitrate in a cell to be used for refining silver in the cell.


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