Mystery salt

[JBo]

Hello Forum,

I just completed one of my gold recoveries from e-waste and I’m seeing a mysterious salt form at the bottom of my waste solution.

Initially, I thought that the solution was just the water rinses of my e-waste after treating the raw scrap with 68% nitric acid to quickly release the gold foils so it was a pail green color. However, upon testing it with some stannous chloride, I got an orange stain indicating platinum in solution. I thought I must have accidentally poured my post gold precipitation solution into it so I put a piece of copper in there overnight to try and cement out any precious metals.

Next morning the solution is dark, deep blue with a mixture of brownish precipitate and some salt-like crystals. It’s hard to tell if the salt crystals themselves are blue or if is just because they’re sitting at the bottom of a blue solution.

I know the blue liquid is probably CuCl2 Copper(II) Chloride. But any ideas what the salt may be?

 

[Yggdrasil]

Hello Forum,

I just completed one of my gold recoveries from e-waste and I’m seeing a mysterious salt form at the bottom of my waste solution.

Initially, I thought that the solution was just the water rinses of my e-waste after treating the raw scrap with 68% nitric acid to quickly release the gold foils so it was a pail green color. However, upon testing it with some standouts chloride, I got an orange stain indicating platinum in solution. I though I must have accidentally poured my post gold precipitation solution into it so I put a piece of copper in there overnight to try and cement out any precious metals.

Next morning the solution is dark, deep blue with a mixture of brownish precipitate and some salt-like crystals. It’s hard to tell if the salts crystals themselves are blue or if is just because they’re sitting at the bottom of a blue solution.

I know the blue liquid is probably CuCl2 Copper(II) Chloride. But any ideas what the salt may be?

CuCl₂ is green so no.
And how do you expect a Chloride to come from Nitric and Copper?
Copper Nitrate is blue.
The pail green is probably to blue/yellow mix from the Copper Nitrate and Nitric in solution.
When you added Copper the blue took over.

The only way Pt can be in solution with Nitric is if you have an PdPt alloy, then the Pt may follow the Pd into solution.
Since this is E-waste there should be no Pt.
Anyway it should be practically non visible, so most likely you have one of the false positives.
It is Stannous Chloride by the way.
The brown

 

[JBo]

CuCl₂ is green so no.
And how do you expect a Chloride to come from Nitric and Copper?
Copper Nitrate is blue.
The pail green is probably to blue/yellow mix from the Copper Nitrate and Nitric in solution.
When you added Copper the blue took over.

The only way Pt can be in solution with Nitric is if you have an PdPt alloy, then the Pt may follow the Pd into solution.
Since this is E-waste there should be no Pt.
Anyway it should be practically non visible, so most likely you have one of the false positives.
It is Stannous Chloride by the way.
The brown

To answer your first question: As I said above, I thought I might have accidentally poured my post Au precipitation waste into my container containing water rinse solution of Copper Nitrate since the stannous chloride test showed an orange stain (indicating Pt). If that were the case, there would have been a much higher concentration of HCl in the solution from the left overs of the aqua regia. That’s why I thought the salt might be Copper Chloride.

But I can’t really tell exactly what color the salt is since it’s in a deep blue solution.

How would I able to tell for sure what the salt is? What would the brown sediment be? (I didn’t add stannous into the solution).

 

[Yggdrasil]

To answer your first question: As I said above, I thought I might have accidentally poured my post Au precipitation waste into my container containing water rinse solution of Copper Nitrate since the stannous chloride test showed an orange stain (indicating Pt). If that were the case, there would have been a much higher concentration of HCl in the solution from the left overs of the aqua regia. That’s why I thought the salt might be Copper Chloride.

But I can’t really tell exactly what color the salt is since it’s in a deep blue solution.

How would I able to tell for sure what the salt is? What would the brown sediment be? (I didn’t add stannous into the solution).

First of all you need to review you lab routines.
Next you need to study so you understand what to expect from your process and your mistakes.
The brown mud will be Copper and what ever PMs was in solution.
The crystals is not possible for us to say anything about.
You are the one in there and the one with the info.
Where did the "waste" come from?

And we never pour or put Stannous into the solution, we always use dropper on paper or cotton bud.

And as said there is no reason to expect Pt if it did not come from very old/ military/ space grade equipment and even then it is rare.

Must likely some reaction with Iron or other false positive.