Non-Chemical Your take on this method for processing pins

[jason_recliner]

You're talking about two different processes. Dissolving base metals in copper chloride leach, or cementing gold out of solution using copper metal. Both can happen together, but they are different. Let me see if I can explain.

In the former, your "AP" leach will be dark as long as there is copper left to dissolve. Air pumped into it will help keep it trending to green, but the copper will keep pushing it to black. Given my personal setups, it's a battle copper generally wins. Once the last of the copper (or other base metal) is dissolved, the black effort stops and the green effort takes over. CuCl2 leach, itself, will not dissolve your gold.

But! If you initially added H2O2, some gold may (will) have been dissolved and will quickly cement out again once it comes across some copper. So you need to dissolve all base metal, then you are left with foils and a little brown dirt, which is also gold.


The other, entirely different, process you mentioned is cementing gold, where you add solid copper bar to a solution of gold. You don't do this with pins in leach.
The copper replaces gold in solution. As the copper dissolves, you'll see it turn darker as the copper dissolves faster than it only cements copper. If you have agitation, and again an air bubbler is good for this, the process will go faster. The aim is not to dissolve all the copper, but to determine when the gold is removed from solution. It stops building up on the copper as powder. Then a stannous chloride test tells you for sure.

 

[FiP]

You're talking about two different processes. Dissolving base metals in copper chloride leach, or cementing gold out of solution using copper metal. Both can happen together, but they are different. Let me see if I can explain.

In the former, your "AP" leach will be dark as long as there is copper left to dissolve. Air pumped into it will help keep it trending to green, but the copper will keep pushing it to black. Given my personal setups, it's a battle copper generally wins. Once the last of the copper (or other base metal) is dissolved, the black effort stops and the green effort takes over. CuCl2 leach, itself, will not dissolve your gold.

But! If you initially added H2O2, some gold may (will) have been dissolved and will quickly cement out again once it comes across some copper. So you need to dissolve all base metal, then you are left with foils and a little brown dirt, which is also gold.


The other, entirely different, process you mentioned is cementing gold, where you add solid copper bar to a solution of gold. You don't do this with pins in leach.
The copper replaces gold in solution. As the copper dissolves, you'll see it turn darker as the copper dissolves faster than it only cements copper. If you have agitation, and again an air bubbler is good for this, the process will go faster. The aim is not to dissolve all the copper, but to determine when the gold is removed from solution. It stops building up on the copper as powder. Then a stannous chloride test tells you for sure.

Thank you for this answer!
All this seems to make sense, thanks.
For continuity sake, if i have questions or obseravtions regarding cementation, i'll move these to another section in the forum.
I'll just get back to the process i was asking for feedback upon
My bests

 

[FiP]

Here is what i did:
Very small experiment (6 or 8 pins)
1st: A bath of 30% hydrogen peroxyde for 1 week with shaking and leaving outside to sunlight in closed clear container.
2nd: emptying the spent Hydrogen peroxyde, allowing time to dry.
3rd: Second bath with copper chloride + fresh Hcl with regular shaking with same storage conditions as above

Results: on the third day (today) i have nice foils

And 2 days later all the base metals had dissolved.

So in all it took around 12 days (7 days in H2O2 30% + 5 days in CuCl+HCl) to dissolve all base metals.
The results gave only floating foils and no sediments or dirt at the bottom.

The quantities recovered are too tiny to get tested and weighed.
As this method doesn't mix H2O2 and CuCl HCl, it's not AP.

For those who have experience using AP on pins does this look average speed or does it look fast? Just for comparison.

Thank you to all to let me know what you think.

I'm thinking to do a 100 g batch with this process and record and weigh everything to see if it's worthwile.

I have a batch of mixed pins from boards, IDE, and mobile phones. Anyone has an idea of an average yield to be expected?

My bests to all

 

[g_axelsson]

Even if you don't mix hydrochloric acid and hydrogen peroxide it's still the process that's called AP. It's just a bad name on a process that should be called the copper chloride process.

Göran

 

[jason_recliner]

So in all it took around 12 days (7 days in H2O2 30% + 5 days in CuCl+HCl) to dissolve all base metals.
The results gave only floating foils and no sediments or dirt at the bottom.
...
For those who have experience using AP on pins does this look average speed or does it look fast? Just for comparison.

It's my opinion that this is about normal, considering the batch. It's faster than mine, but though you didn't have an air bubbler, you also had a unusually low ratio of volume to surface area; this would take on oxygen quite well.

I don't really think your peroxide pre-processing added anything. If you want to be sure, just for science sake, run a control test identically in every way except the peroxide. Or preferably two new tests, with the CuCl2 leaching done side by side.

 

[FiP]

So in all it took around 12 days (7 days in H2O2 30% + 5 days in CuCl+HCl) to dissolve all base metals.
The results gave only floating foils and no sediments or dirt at the bottom.
...
For those who have experience using AP on pins does this look average speed or does it look fast? Just for comparison.

It's my opinion that this is about normal, considering the batch. It's faster than mine, but though you didn't have an air bubbler, you also had a unusually low ratio of volume to surface area; this would take on oxygen quite well.

I don't really think your peroxide pre-processing added anything. If you want to be sure, just for science sake, run a control test identically in every way except the peroxide. Or preferably two new tests, with the CuCl2 leaching done side by side.

Hello,

This seems to make a lot of sense! Low ratio volume to surface area could explain this very well.
And making 2 tests with the same set up seems to be a wise way to know for sure.

Thanks for your help and input.

My bests

 

[FiP]

That colour is characteristic. If you were to add oxygen, through a fish bubbler, you'd likely find it turn green again.
As long as there is any undissolved base metal, that metal will keep using up the free CuCl2 and keeping your solution dark.
So my recent take on this is that it's only after it finally turns green - and is oxygenating again - that you can be really sure all base metal is dissolved.

Thanks for that
I'm not so sure about this aspect since i have cemented some solutions and with copper tubing in them they went completely clear (see through green), and when i took it out it went dark again... Maybe it has something to do with exposure to light?

My bests

Hello Jason,

I found this aspect interesting so i tried to investigate and experiment.
I asked around but got no proper explanation.

In my experiment i did this: take some green CuCl2 solution. Added some copper to it. After some time it got clear (no color at all). I removed some of the solution to a clear, empty, container. I could then observe from the surface of the solution that it started to get a green colour.
My conclusions: when "saturated" with copper, a solution turns clear.
Contact (or maybe forced contact with air (probably O2)) will bring the colour back (green).

As to the use of a CuCl solution with that much copper in it, i found it to be less reactive: to get it to leech to a "normal expected rate" it needs to be combined with a consequent amount of fresh HCl.

These were my findings, where are at you a with this?
If anyone has any light to shed on this, i'm eager!

Best to all!

 

[jason_recliner]

In my experience, the typical behaviour of CuCl2 is that if you add more copper metal it will turn from green to a very dark brown.

But one of my early errors was to throw everything I had into a pickle jar of acid. There, I noticed a distinctive stratification; a completely clear layer under the dark brown layer. This clear layer was likely saturated with zinc or tin or something else more reactive than copper. Could this be happening to you?

 

[goldsilverpro]

That colour is characteristic. If you were to add oxygen, through a fish bubbler, you'd likely find it turn green again.
As long as there is any undissolved base metal, that metal will keep using up the free CuCl2 and keeping your solution dark.
So my recent take on this is that it's only after it finally turns green - and is oxygenating again - that you can be really sure all base metal is dissolved.

Thanks for that
I'm not so sure about this aspect since i have cemented some solutions and with copper tubing in them they went completely clear (see through green), and when i took it out it went dark again... Maybe it has something to do with exposure to light?

My bests

Hello Jason,

I found this aspect interesting so i tried to investigate and experiment.
I asked around but got no proper explanation.

In my experiment i did this: take some green CuCl2 solution. Added some copper to it. After some time it got clear (no color at all). I removed some of the solution to a clear, empty, container. I could then observe from the surface of the solution that it started to get a green colour.
My conclusions: when "saturated" with copper, a solution turns clear.
Contact (or maybe forced contact with air (probably O2)) will bring the colour back (green).

As to the use of a CuCl solution with that much copper in it, i found it to be less reactive: to get it to leech to a "normal expected rate" it needs to be combined with a consequent amount of fresh HCl.

These were my findings, where are at you a with this?
If anyone has any light to shed on this, i'm eager!

Best to all!

You didn't think this out very well. Did you notice any whitish powder?

The solubility of CuCl2 in water (~700g/l) is about 11,000 times greater than the solubility of CuCl in water (~.06g/l). Were you to add solid white CuCl to water, the solution (super weak - .06g/l) would be essentially colorless. CuCl will dissolve in free HCl, forming the green CuCl2. The Cu you added to the CuCl2 reduced the CuCl2 to CuCl and that's why it cleared up - most all of the CuCl precipitated.

In a wrong way, you are right. The copper, as CuCl, was "saturated" in the clear solution. However, it would take ~6 gallons of water to dissolve 1 gram of Cu, as CuCl. Were you to "saturate" water with the yellow CuCl2, it would pick up a couple of waters of hydration and become, in solution, the green CuCl2.2H20. If you crystallized this out gently, you would likely have green CuCl2.2H2O crystals. In that case, at saturation, 6 gallons of water would contain ~41 pounds of copper. When Jason added copper, it might have reduced the Cu-2 further than Cu-1 to Cu metal powder, which is a reddish-brown color. Note that red and green make brown.

 

[g_axelsson]

That colour is characteristic. If you were to add oxygen, through a fish bubbler, you'd likely find it turn green again.
As long as there is any undissolved base metal, that metal will keep using up the free CuCl2 and keeping your solution dark.
So my recent take on this is that it's only after it finally turns green - and is oxygenating again - that you can be really sure all base metal is dissolved.

Thanks for that
I'm not so sure about this aspect since i have cemented some solutions and with copper tubing in them they went completely clear (see through green), and when i took it out it went dark again... Maybe it has something to do with exposure to light?

My bests

Hello Jason,

I found this aspect interesting so i tried to investigate and experiment.
I asked around but got no proper explanation.

In my experiment i did this: take some green CuCl2 solution. Added some copper to it. After some time it got clear (no color at all). I removed some of the solution to a clear, empty, container. I could then observe from the surface of the solution that it started to get a green colour.
My conclusions: when "saturated" with copper, a solution turns clear.
Contact (or maybe forced contact with air (probably O2)) will bring the colour back (green).

As to the use of a CuCl solution with that much copper in it, i found it to be less reactive: to get it to leech to a "normal expected rate" it needs to be combined with a consequent amount of fresh HCl.

These were my findings, where are at you a with this?
If anyone has any light to shed on this, i'm eager!

Best to all!

You didn't think this out very well. Did you notice any whitish powder?

The solubility of CuCl2 in water (~700g/l) is about 11,000 times greater than the solubility of CuCl in water (~.06g/l). Were you to add solid white CuCl to water, the solution (super weak - .006g/l) would be essentially colorless. CuCl will dissolve in free HCl, forming the green CuCl2. The Cu you added to the CuCl2 reduced the CuCl2 to CuCl and that's why it cleared up - most all of the CuCl precipitated.

In a wrong way, you are right. The copper, as CuCl, was "saturated" in the clear solution. However, it would take ~6 gallons of water to dissolve 1 gram of Cu, as CuCl.

I'm with GSP on this, just one slight detail I'm objecting to and would like to expand on...

CuCl will dissolve in free HCl, forming the green CuCl2 when you have excess oxygen. When you are in an oxygen free environment it only complexes with the chloride ions and usually forms the brown CuCl in solution.
Your initial dissolving of the copper tube gave you CuCl that used up the oxygen in the solution to form more CuCl₂, that dissolved more copper until the supply of oxygen and CuCl₂ was depleted and the dissolving halted.
When you put it in a separate beaker the oxygen from the air diffusing into solution turned the small amout of CuCl into CuCl₂ when it reacted with the oxygen, giving the green color.

Fip, if you have had a lot more HCl in solution it would have turned brown instead of clear. Then done the transformation into a much more deeper green when sitting in a separate beaker as there would have been a lot more copper in solution. Just like your initial observations when removing the bubbler turned the solution dark.

Göran

 

[goldsilverpro]

Goran,

CuCl will dissolve in free HCl, forming the green CuCl2 when you have excess oxygen. When you are in an oxygen free environment it only complexes with the chloride ions and usually forms the brown CuCl in solution.

I disagree.

CuCl2 is yellow, not green. Only the hydrated form is green. I can't see how oxygen enters into it. CuCl isn't brown unless it's contaminated with something like copper powder or dirt. CuCl is white. It's been awhile but, when you add an excess of SMB to an AR soln, you often get an off-white (white plus dirt probably, CuCl precipitation.

I will edit my first post to correctly read: forming the green CuCl2.H20 (in place of CuCl2). CuCl2 is yellow.

The compounds, colors, and solubilities all came from the CRC Handbook. This book is about the "last word". In that book, white always means white, yellow means yellow and green means green - not, for example, off-white, brown, and blue-green.

EDIT: I found this interesting. I just read that, with concentrated HCl and a little potassium chlorate, copper turnings are dissolved, forming a black solution at first, which ultimately becomes completely colorless. On dilution, the salt precipitates as the snow-white pure CuCl, which turns greenish in moist air (CuCl2.H2O). In other words, CuCl is fairly soluble in concentrated (only) HCl. Reminds me of Lou's HCl, AgCl removal from Au powder method, sort of.

 

[g_axelsson]

Goran,

CuCl will dissolve in free HCl, forming the green CuCl2 when you have excess oxygen. When you are in an oxygen free environment it only complexes with the chloride ions and usually forms the brown CuCl in solution.

CuCl2 is yellow, not green. Only the hydrated form is green. I can't see how oxygen enters into it. CuCl isn't brown unless it's contaminated with something like copper powder or dirt. CuCl is white. It's been awhile but, when you add an excess of SMB to an AR soln, you often get an off-white (white plus dirt probably, CuCl precipitation.

I will edit my first post to correctly read: forming the green CuCl2.H20. CuCl2 is yellow.

The compounds, colors, and solubilities all came from the CRC Handbook.

I won't argue against CRC, that's a good book...
...but I would assume that CuCl₂ in solution is quite hydrated. :mrgreen:

Oxygen enters into the equation as...
4 CuCl + 4 HCl +O₂ = 4 CuCl₂ + 2 H₂O
You need something to take the excess H or the copper wouldn't go from +1 to +2 oxidation state. That's why people uses a bubbler to oxygenate copper chloride leach.

Precipitated (solid) CuCl is white. The color of CuCl in solution, when complexed with a high Cl^- ion solution is dark brown as can be seen when running low on oxygen. If enough CuCl goes into solution some is oxidized into CuCl₂ but when the oxygen is gone it is starting to color the solution dark brown / black.
Since you only need a lot of Cl^-, even saturated NaCl solution will dissolve quite a lot CuCl. So basically a strong CuCl₂ should be able to dissolve a lot of CuCl too.

But I agree, in pure water the solubility of CuCl is very low. It can be seen when you have a dark brown solution close to saturation and add a bit of water. That precipitates a cloud of white CuCl.

The effect of CuCl in the CuCl₂ can be seen in the document on Lazersteve's site.
http://www.goldrecovery.us/%5Cgoldrecovery%5Cdocuments%5CCuCl.pdf (login is required)
On page 10 there is a nice series of concentrations, showing the color change.

Göran

 

[goldsilverpro]

According to this article
http://www.rsc.org/suppdata/ta/c2/c2ta00138a/c2ta00138a.pdf

the CuCl complexes with the HCl according to the following equation
CuCl + xHCl = H_xCuCl_1+x, Where x is 1 or 2, HCuCL₂ or H₂CuCl₃

That's where the H goes. No oxygen involved. You're right, though, in that oxygen is required if you want to produce CuCl2 (actually CuCl2.H2O) from CuCl in the presence of HCl.

The more I look at this, the more I think we're approaching this from 2 totally different angles. Sort of like apples and oranges.

 

[g_axelsson]

According to this article
http://www.rsc.org/suppdata/ta/c2/c2ta00138a/c2ta00138a.pdf

the CuCl complexes with the HCl according to the following equation
CuCl + xHCl = H_xCuCl_1+x where x is 1 or 2

That's where the H goes. No oxygen involved.

But that's still only CuCl + HCl in a complex, you posted CuCl₂ above and to get to that oxidation state you need an oxidizer. Most people here use oxygen or peroxide (but you could also use Cl₂). You need to keep track of the oxidation state of that copper atom.

CRC says that CuCl is soluble in HCl (or NH4OH), not HCl + O2. If oxygen were required, it would have said so.

I never said you needed oxygen to dissolve CuCl. The oxygen is used for turning CuCl into CuCl₂ in the step that refreshes the leach to be able to dissolve more metallic copper. The only thing needed to dissolve CuCl is a solution rich in free Cl^- so even concentrated NaCl can do it. This I have tried and it worked, but HCl is more effective.

If the only step needed to turn CuCl into CuCl₂ is addition of HCl we would get a reduction of the H⁺ to balance the oxidation of copper. That would release H₂ as gas and I've never seen that happen. We need an additional oxidizer for that step, CuCl and HCl doesn't have enough energy to do that by themselves.

Göran

 

[goldsilverpro]

I finally see what you were saying about my statement of CuCl + HCl = CuCl2. I erred and will correct it.

What is brown CuCl?

 

[g_axelsson]

I finally see what you were saying about my statement of CuCl + HCl = CuCl2. I erred and will correct it.

What is brown CuCl?

Then we are on the same page.

Did you have a look at the copperchloride document on Lazersteve's site?
This is the picture on page 10 that I was talking about.


That document is for copper chloride etching what Hoke is for refining. It doesn't tell you exactly what you need but gives enough background for you to understand what is happening.
First time you read it you probably don't recognize what it tells you, but coming back to it while experimenting and suddenly you get it, how good it actually is.

Göran

 

[FiP]

Hi,

I thank you all for having taken the time to expand on that and shared the knowledge.
I'm still curious about one aspect: i see that when i remove solid copper from the clear solution, it goes back to green-brown. Anybody knows why, i found that funny.

My bests

 

[g_axelsson]

Hi,

I thank you all for having taken the time to expand on that and shared the knowledge.
I'm still curious about one aspect: i see that when i remove solid copper from the clear solution, it goes back to green-brown. Anybody knows why, i found that funny.

My bests

When you have a copper tube in it, all CuCl₂ is used up dissolving copper. In solution is only CuCl. Oxygen is depleted by oxidizing CuCl into CuCl₂ but dissolving copper stops the CuCl₂ to build up.

When you remove the tube the oxygen oxidizes CuCl into CuCl₂ and the CuCl₂ starts to build up, which you see as a change in color.

Göran

 

[FiP]

Hi,

I thank you all for having taken the time to expand on that and shared the knowledge.
I'm still curious about one aspect: i see that when i remove solid copper from the clear solution, it goes back to green-brown. Anybody knows why, i found that funny.

My bests

When you have a copper tube in it, all CuCl₂ is used up dissolving copper. In solution is only CuCl. Oxygen is depleted by oxidizing CuCl into CuCl₂ but dissolving copper stops the CuCl₂ to build up.

When you remove the tube the oxygen oxidizes CuCl into CuCl₂ and the CuCl₂ starts to build up, which you see as a change in color.

Göran

Thanks,

Following the reasoning from above posts, i understand.
With the solid copper in, my solution has vitually no color though.

FiP

 

[goldsilverpro]

I have a copy of the article that Goran mentioned (CuCl.pdf) and have posted it here, along with 2 other articles in my files.

I have never used the AP method (or even played around with it) and probably never will, at least as long as I can buy cyanide (1st choice, without a doubt). With no cyanide, I would probably buy a barrel plater (tumbler) and use the sulfuric stripper (2nd choice) or nitric (3rd or 4th choice). I might even give a KI/I2 or KBr/Br2 stripper a shot. I find it hard to even consider a process if I don't think it will be profitable on a large scale.