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Copper recover from acidified copper nitrate (etching with nitric acid)

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Mosaic

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I etch with dilute nitric about 3:1 mixdown from fuming HNO3. I like it because it's clear, doesn't stain and skin can tolerate it for up to 15 seconds with no irritation. Ask me how I know...been using it 30 years now.:rolleyes:

So rather than dumping the solution when it gets dark blue and slows etching...I decided to reconstitute the nitric acid by electroplating the copper out.

Using graphite plates I proceeded to execute this idea...it worked for a while (@ 3A/sq in current density) with good agitation from oxygen production on the anode until the solution heated up due to current flow...then the plated copper dissolved back into the solution at around 40°C.

So temperature accelerates the etching and defeats the plating.:banghead:

Trying to plate with low currents probably won't work too well as the etch vs plating balance would be found quickly and plateau out.:(

So phase 2. Place the electroplating cell in the freezer :cool: (I have a workshop fridge for preserving acrylic glue, PVC cement, solder paste etc), and try again...
 

large_ghostman

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I know when mixed with Sulphuric acid you can deposit the copper simply by placing iron in the solution, I have never tried with just Nitric acid. But copper Nitrate might deposit the copper onto iron. Having said that I rarely use dilute Nitric and my copper comes from metal recovery.

Actually dosnt sound right, let me check first.
 

large_ghostman

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Ok you can do with electro plating, both terminals carbon, remove the copper regularly from the cathode, you wont get 100% removal though.

You can displace with Iron or Aluminium, but you get Ferrous Nitrate or Aluminium Nitrate. The other ways are a bit more involved chemically.....

Heat the copper nitrate so that NOx brown gas comes off, feed that into cold water, isnt as pure nitric acid but its fine to remove copper, or you can distil it. The your left with Copper Oxide, this you can return to copper by heating with Hydrogen atmosphere.
2 Cu (NO3)2 → 2 CuO + 4 NO2 + O2
3NO2 + H2O → 2HNO3 + NO

CuO + H2 → Cu + H2O
Removed the Carbon monoxide route because I hadnt given it as an option.

OR

You could mix the copper Oxide with hydrochloric acid to make Copper chloride, thats a fairly good etchant itself.

CuO + 2 HCl → CuCl2 + H2O

I would drop the Amps to ~1 if you use electrolysis and the Voltage under 5V, 4.8 ish is about right. Actually drop to 4V and 3 A should do it. But you need to keep removing the copper from the Cathode.
 
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large_ghostman

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Wrong, wrong, and wrong. When did this forum devolve into utter nonsense?
At the same moment people stopped giving an explanation, and started just stating something was wrong without any further information, or around 5:01 Am looking at your post. Ok if I am wrong correct it, That is of far more use than stating something is wrong without explaining why.
 
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large_ghostman

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I couldnt be bothered to get a paper source, so hopefully you will except wiki!

For the copper nitrate to copper oxide
https://en.wikipedia.org/wiki/Copper(II)_oxide

And for the reduction of copper II oxide by Hydrogen (other gases can be used) this should do as a reference.

http://www.rsc.org/learn-chemistry/...copper-ii-oxide-by-hydrogen?cmpid=CMP00002420

So care again to actually explain what is wrong and why? Or you just wanted to up your poor post count?

Just in case your one of those really picky people, here is a reference for copper chloride as an etchant, I assumed considering the level of knowledge here, I didnt need to reference as most would be able to read the reactions etc. Anyway just incase you want to argue the copper chloride etchant

http://www.chemcut.net/wp-content/u...letin_8_Cupri_Chloride_Proces_-Parameters.pdf

Or maybe something else is wrong? Very hard to tell, it seems your using the old system of posting. The one where you give zero information as to what your referring too, normally practised by those who dont want to have to back anything up. You may of missed it, but we try very hard to give information rather than state something without giving a single to what your on about.
 
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Mosaic

Well-Known Member
Well...I desisted as passing current thru the copper nitrate (acidifed) heated it...by the time it reached 40C (in the fridge) it was active enough to remove the copper plated onto the graphite. O well...
 
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