Gold Plated EWaste Pins

[solar_plasma]

As far as I read in my books, there is no such thing as a CuCl₃ or CuCl₄ and I didn't talk about that in any way.

In no way I said, it should be brown and would still work. I even showed the reason, why it stops etching, the more brown it gets.

You can't understand what I meant as long as you use the simplified model, but you have to think of oxidation states and complexes.

This way to look at things is not necessary for those, who just want to make it work, but for those, who wants to know the "why" just for the curiosity. As far as I can see, this is the most advanced explanation given, but I am open for discussion.

 

[Geo]

From my understanding, there's only two ways to have brown copper in copper(II) chloride solution, (1) undissolved copper metal and (2) copper(I) oxide. If anyone comes up with a better explanation, please let me know. Either way, add more HCl.

 

[solar_plasma]

Both of them are not soluble. So, how can the solution be green-brown even after filtering and/or settling?

You know I do like you and I, too, don't want to sound harsh, but you are just telling Wiberg's Inorganic chemistry is wrong.

 

[Geo]

Hey, that's my point. :lol: It can't be brown. If CuCl2 turns brown, then the copper metal is coming out of solution. If it was dissolved, it is coming out as copper oxide. If the metal has been chewed up by the previous chemical action, undissolved copper can be free floating. Either way, the brown color is not a copper chloride salt.

Copper(I) chloride is a solid white crystal. copper(II) chloride is a green crystal or green liquid. Neither of these two chlorides are brown.

 

[solar_plasma]

concentrated CuCl2 in HCl acidic environment -> greenbrown [CuCl4]2^- <------this is still Cu⁺⁺!

Holleman/Wiberg Inorganic Chemistry, XXII. Copper group, 1.3 copper(II) compounds, copper(II)chloride

So, as long there is anything green in it, it will etch, but of course it will slow down, when the excess HCl is used up, since the copper chloride system only works as a catalyst, but it is the HCl that does the work on the long run.

It should not wonder if copper metal forms, especially if more reactive metals are present, but I looked at a pure copper system.

 

[Geo]

Electronics will seldom be pure copper.

If I placed some copper metal in a container and added a small amount of copper oxide, I would have created AP solution. If the solution is left undisturbed, either the copper will dissolve (if there's enough acid) or, only the amount of copper the solution can hold (saturation point) will dissolve. Any added energy, (temperature changes (heat) or stirring (vibrations) will effect how much copper the solution will dissolve. If the temperature rises, the solution dissolves more. As the solution cools, the excess copper will precipitate out as CuCl (a white powder). If the solution reaches it's saturation point and the reaction depletes the solution of hydrochloric by either heating and cooling or adding oxygen and then stopping the oxygen, brown copper oxide will precipitate out.

 

[solar_plasma]

I have no doubt about the phenomenon as it is perceived. About the reactions and compounds I am more cautious to jump at conclusions. Maybe I find a way to implement your point into the theory from the books.

 

[jeneje]

I never seen where he said they were copper pins (i think we all assume they are) they may be plated over iron. If they are, the solution will turn brown as the HCL used in the AP dissolves the iron into solution. If adding air with more HCL doesn't re-dissolve the copper then i would suspect iron. Just a thought. :|
Ken

 

[solar_plasma]

Most likely.

I can't see any reason, why a pure copper chloride system should reduce copper to anything else but CuCl or its complexes in solution.

Iron, nickel and zinc might, though. And a lot of brown iron compounds will possibly be involved,too.

 

[g_axelsson]

Hey guys! Slow down! Ten additional replies while I've been researching my answer... gee, talk about being left in the dust... :mrgreen:
I'm going to post this as it is and then read the rest of the replies.

Göran, I'm going to have to disagree with that. I've been using copper chloride for about four years and I've never seen brown copper chloride. There is brown copper chloride that I have found out but it is copper chloride anhydrous. Since copper(I) chloride is a white solid, and copper(II) chloride is a green liquid and green crystal, what copper chloride could it be if it's brown but still in solution. Green copper(II) chloride is what you want you etching solution to look like. It may get murky with copper(I) chloride when the solution gets saturated or if the PH rises above the limit of the solution to hold it in solution. Copper oxide will deposit then. I believe the brown is copper metal colloid in the solution. Not enough HCl to keep it dissolved.

Well, I have run copper chloride since Steve brought the process to the forum. I made some big mistakes from the beginning before it was realized that too much peroxide also dissolved gold. I might not run the fastest process since I've never bothered about speed and got scared of dissolving gold from my first runs.

Copper(I) chloride is not soluble in water, but in a high chloride matrix it is (for example HCl, NaCl or even AuCl₃ though I haven't tested that one yet!)

If you take a look at the _goldrecovery_documents_CuCl.pdf document at Lazersteves site you have on page 10 a nice picture of Cu¹⁺ ions in solution in a Cu²⁺ etchant. At 4g/liter it has a clear brown tone and at 10g/liter it is definitely brown.

CuCl can be dissolved in concentrated HCl to form colorless(!) H[CuCl₂] (this is Cu(I) or Cu⁺!)

(source: Holleman/Wiberg)

Now, let's think of all the possible combinations and the other metals involved...so, let's stay assuming a clean copper solution.

The brown color is obviously not CuCl, copper(I) is colorless, but from experience we know, the more Cu dissolves, the more dark the solution gets, while c_HCl decreases. More HCl in an oxidizing environment is needed, obviously to bring complexed Cu(I) back to Cu(II).

If we think of precipitated white/grey CuCl, it is easier to describe, what will happen:
CuCl + HCl -> H[CuCl₂]
then
H[CuCl₂] -> CuCl₂ (actually complexed) + e^-

So, saying the brown color is from dissolved CuCl is a simplification, which works well enough for our purpose. Saying CuCl is never brown, but colorless, is also correct. I think both of you are right and wrong from a point of view.

That last formula isn't balanced. Shouldn't it be
H[CuCl₂] -> H⁺ + CuCl₂^- (+something about complexed)

Anyhow, I had a hard time finding anything about the color except from Steves page. Then I found "Handbook of Copper Compounds and Applications" (Google books) and it states :
"The colorless solution contains essentially copper(I) ions. Small amounts of copper(II) ions in the presence of copper(I) ions darkens the solution significantly and it is suspected that a charge transfer between the copper(I)-copper(II) complex is responsible for the intense coloration."

Maybe the CuCl isn't responsible for the color by itself, but it seems it is an integral part of the coloring and that it can be used as an indicator of how high the concentration is.

After reading through many of these documents again I agree, running with high concentration of CuCl will slow the process down. Seems we all were correct in parts. 8)

Göran

 

[solar_plasma]

Hey you're right, I missed that H. Maybe something like that:

^-[CuCl₂] -> CuCl₂ (actually complexed) + e^-

Thanks for the link! It looks as if all of us are into some valuable points. And the synthesis of those points seems to bring us closer to the understanding of the whole as is.

 

[solar_plasma]

Take a look at p.69, electrolysis of CuCl:

It seems to be possible to dissolve base metals at the anode without chlorine evolution and deposit copper metal at the cathode. That leaves only the question, if gold plating will dissolve, too, because of the oxidizing environment. If not, this could be a nice CuCl₂-etchant modification.

edit: I think I'll try this as my next project with a concentrated, spent solution, very low voltage (0,679V?) and maybe some kind of diaphragm.

 

[g_axelsson]

Yes, I found out about that 2 CuCl -> Cu + CuCl₂ electrolysis process when researching electrowinning from a chlorine solution a couple of months ago. Just as you write, the problematic part is chlorine production and attack of the electrode. I was going to write about it but haven't had time to do any experiments yet.
I don't think the gold plating will dissolve if you use the CuCl₂ for etching and if it did it would end up with the copper and that we could run in a copper (sulfate) cell without problem after melting the pure copper.
You could pump the renewed copper(II) chloride into a leach vat and draw off spent solution of copper(I) chloride in a continuous operation or batch wise renew the etchant.

There isn't a lot written on electrowinning from chloride solutions but at least I found this article.

Have fun! 8)

Göran

 

[solar_plasma]

I love it! This text contains a lot of information I was longing for. Thanks!

I have to re-read it several times to see, in what direction it affects the idea of an electro-renewing CuCl2/CuCl reactor for the purpose of dissolving base metals under gold plating or even de-plating thick pieces.

Your idea with a second tank might be the way to go. A pipe with an air bubbler could be used as an acid resistant pump, just like in small cheap fish tanks. The flow back could be achieved by gravity. If just chlorine evolution can be completely suppressed...

But only using one chamber would have the advantage that the CuCl₂ would get used as soon as it evolves, dissolving the base metals of the gold scrap anode. And my stomach says, this could prevent chlorine evolution.

 

[Redsox1901]

View attachment Attachments_20141122.zip

I have included an attachment of pics so you can see what I am talking about. Any assistance would be greatly appreciated.

 

[kurtak]

solar, Geo, Goran

I just love reading the discussions you guys have - I learn a lot from them 8)

Kurt

 

[g_axelsson]

I love it! This text contains a lot of information I was longing for. Thanks!

I have to re-read it several times to see, in what direction it affects the idea of an electro-renewing CuCl2/CuCl reactor for the purpose of dissolving base metals under gold plating or even de-plating thick pieces.

Your idea with a second tank might be the way to go. A pipe with an air bubbler could be used as an acid resistant pump, just like in small cheap fish tanks. The flow back could be achieved by gravity. If just chlorine evolution can be completely suppressed...

But only using one chamber would have the advantage that the CuCl₂ would get used as soon as it evolves, dissolving the base metals of the gold scrap anode. And my stomach says, this could prevent chlorine evolution.

I don't think you should use air to transport the copper(I) chloride, you want it to remain unoxidized. If you allow oxygen to it then you get copper(II) chloride and that you can't electrowin without releasing chlorine gas.

If you have the electrowinning unit inside the leaching vat then you risk getting free floating gold foils to deposit on the copper and become embedded. A filter bag would solve that problem easily.

The electrolyte would need to be replenished regularly as zinc, iron, nickel.... and so on would rob it of copper, but this is a perfect way to use up all our old copper chloride waste. 8)

Göran

 

[Anonymous]

solar, Geo, Goran

I just love reading the discussions you guys have - I learn a lot from them 8)

Kurt

I was going to post something but Kurt you said it better than I could have done. So I didn't. I love the good natured disagreements and info gained from them. Thanks lads.

 

[Redsox1901]

So does anyone have any ideas on how I can fix my mistakes? I am not even quite sure what the problem is. Us there a way to test for problems? I have been reading threads all day and haven't found the answers.

Thank you

Joe

 

[Geo]

So does anyone have any ideas on how I can fix my mistakes? I am not even quite sure what the problem is. Us there a way to test for problems? I have been reading threads all day and haven't found the answers.

Thank you

Joe

It looks like the solution dissolved something but it's not copper. Decant the solution and take a piece of the metal and wipe it off good and make sure the gold plating is still intact. The amount of solution in the pictures is good. If the plating is still intact, add it all back to the container and add a small amount of H2O2 and watch for a color change in the solution. It should go clear and then some shade of green. Add an oxygen source like a fish aquarium pump. It wouldn't hurt to find some green copper oxide to add to the mix.