Gold Plated EWaste Pins

[Redsox1901]

Hello I am really new to the site but have a great interest in refining metals. I have tried to look for any information on removing the gold plating from computer ewaste. I understand the concept of using AP for removing the foil fingers from boards and why that is done. I would really just like some guidence on where on the forum to look or some information regarding if AP and then acid/clorox would be the best technique for disolvong the plating from the pins. I was thinking about using AP to make sure that the pins are free of copper and then soak them in acid/clorox to dissolve the gold in solution. Once that is done I will precipitate it out. Please let me know if this makes sense.

Thank you!

 

[Pantherlikher]

Hello and welcome to the forum.
Before touching any acid, please learn the right way to do what you are hoping to do from start to finish...
Meaning read through the forum until you know what to do when acid splashes all over you or fumes take your breath away...
Also what to do with spent acids when you are done.

Below is 2 links? URLs I found simply by typing Pins into the google custom search up top.
There you can type anything in and will show links to posts on the subject.
What you find is older posts first and has loads of good background on subject of choice.
Reading through them you will find that the processes have become fine tuned to work best.
These 2 links covered using acid to remove all base metal from pins but this is Not the best way to do most pins.
Good reading though.


http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=37&t=1545
http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=39&t=13815

Good luck and hope you learn the right way.

B.S.

 

[Redsox1901]

Thank you so much for the very useful links. I have a lot to learn but safety always comes first. I have a lot of pins from 3 main sources. Hard drives, mother boards and cd/dvd roms. So I am figuring probably copper with a coating of nickel with the gold plate? Will continue to read but if you have any hints please let me know.

 

[g_axelsson]

Just one tiny detail, it should be copper based mostly, brass or bronze. Pure copper is too soft for a normal connector and would bend easily. Pins can also be iron based, for example covar pins on IC circuits.

You are correct when you note there is a nickel barrier layer between the gold and the base metal, at least on copper based pins.

Göran

 

[Redsox1901]

The AP should dissolve the brass/bronze in solution. The crock pot will probably be the fastest correct? Also, what should I use to dissolve the nickel?

 

[kurtak]

be sure not to use to much peroxide in your AP or you will dissolve gold before you want to - the peroxide is only used (small amount) to kick start the reaction of copper 2 chloride

Kurt

 

[Redsox1901]

Thank you. I was planning a 3:1 solution HCL to Peroxide. From everything I have read this sounded reasonable. Do you concur?

 

[FrugalRefiner]

Cover your scrap with HCl. Add a capful of H₂O₂. Be patient while the reaction gets started. Then, add an aquarium bubbler.

Dave

 

[Redsox1901]

I will certainly try that! Thank you so much for the suggestion. I am also taking a neodymium magnet to the pins to confirm there is no ferrous materials as a base metal. From what I have read any ferrous material can really foul up the AP bath? What would be an alternate solution for gold plate over ferrous? And would you also take a magnet to it?

Thank you!

 

[maynman1751]

If you use a powerful magnet it will also attract the non ferrous pins because of the nickel plating which is somewhat magnetic. If you are going to use a magnet to separate, use a weaker one.

Do a search for an electrolitic cell. It's the best way to do pins. Be careful with this method as it uses a very dangerous acid (sulfuric). Know what you're doing before attempting this method!!!!!!

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=18365&hilit=sulfuric+cell

 

[Redsox1901]

I want to thank everyone for their help. I am going to start the process and will let you all know. Thank you again.

 

[Redsox1901]

Ok, so i have covered the pins with the HCL and added a little H2O2. I gave it 2 days to get going at which point it was the nice emerald green everyone talks about. I then added an aquarium bubbler which has been in for 3 days now. The solution is now a brown color. I understand this to be the Copper dissolving in the solution. Just to be on the safe side I tested the solution with Stannous Cloride to confirm if any gold was dissolved (even though i only used a small amount of H2O2). Is it the correct thing to do to add more HCL to allow for more copper to be dissolved.

 

[Geo]

Ok, so i have covered the pins with the HCL and added a little H2O2. I gave it 2 days to get going at which point it was the nice emerald green everyone talks about. I then added an aquarium bubbler which has been in for 3 days now. The solution is now a brown color. I understand this to be the Copper dissolving in the solution. Just to be on the safe side I tested the solution with Stannous Cloride to confirm if any gold was dissolved (even though i only used a small amount of H2O2). Is it the correct thing to do to add more HCL to allow for more copper to be dissolved.

Brown is not good in AP solution. Add more HCl even if you have to move it to a bigger container.

 

[Redsox1901]

Geo,

So I've moved it to a bigger container and added more HCL. Should I expect the solution to turn back to green or just a lighter brown?

 

[g_axelsson]

I think brown is okay, it is CuCl in solution. The only thing it tells you is that the solution is working and dissolving copper but it is lacking in oxygen. If you get a white sediment then it is undissolved CuCl and you need to add more HCl. CuCl needs free HCl to dissolve so the fact that the solution is brown without sediments shows it is enough HCl for the moment.
Either add more air or more patience, the copper chloride process needs a lot of the latter.

The solution turns brown with just a little bit of CuCl in solution, look at the documents on Lazersteves homepage for a color guide to the copper chloride process.

Göran

 

[Redsox1901]

Well I guess its a good thing that I do not have any white sediment at the bottom. I have noticed a lot of gold foil floating in the solution so that is also pretty good. I really think my problem is that a lot of the pins I put to solution had a lot of the base metal remaining which is now dissolved. The extra base metal would add more dissolved copper to the solution causing the browning. I have had the aquarium bubbler going 24 hrs a day for 3 days now so the amount of base metals being dissolved should be quite a bit. Please let me know if anyone has any suggestions on how I should proceed.

 

[Geo]

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.

 

[solar_plasma]

It is oversimplified only to think of CuCl + Cl^- <=> CuCl₂, when it comes to the colors of the solutions.

In fact there are a lot of different complexes forming, depending on the concentrations, pH, ORP and the amount of excess HCl.


dilluted CuCl₂ -> slightly blue [Cu(H₂O)₆]²⁺
medium concentrated CuCl₂ -> green [CuCl₂(H₂O)₄]
concentrated CuCl₂ in HCl acidic environment -> greenbrown [CuCl₄]^2-

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] (complexing)
then
H[CuCl₂] -> CuCl₂ (actually complexed) + e^- (oxidation)

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.

 

[Geo]

Notice that I said that if the PH rises above the point that the copper in solution precipitates as an oxide, what color is copper(I) oxide? http://en.wikipedia.org/wiki/Copper(I)_oxide To adjust the PH back down to where the solution can hold the added copper, add more HCl. Copper(I) chloride (CuCl) and copper(II) chloride (CuCl2) and that's it. There's debate about the possibility of CuCl3 and CuCl4 but it's so unstable, for all intents and purposes, there's no reason to suspect it. If the solution is brown, it is not doing it's job as an etchant. The chemistry is off and something has gone wrong. The attitude that the brown color is as it should be bothers me because it is such a simple process. I don't mean to be harsh but copper(II) chloride (CuCl2) etchant, is what it is, and it should be promoted for what it is and as it should be. If we tell people that AP is working when it is brown is not true and is misinformation. I have friends that whisper in my ear when I make mistakes and I very much appreciate it but I also get called out on the things I say that are incomplete or completely wrong. Even a process as simple as AP can be chocked full of problems and dangers. Why stress over a high profile process like dissolving gold and so little effort into something like dissolving copper.

 

[solar_plasma]

Sorry, I added some lines for better explanation before I saw, you already answered.

I think now it should be better to understand. Yes, we can look at it using a simplified model. Everybody knows, this model is enough for doing our work.

BUT you guys raised the question about the color and this is quite not that trivial.