Dropping gold and palladium selectively from thiourea solution

[domus1212]

Hi,

I'm new here and didn't find a topic with working on thiourea.

I've leach the gold in tiosulphate with catalizators (ph = 11,86) and later put it on weak-base resin. Later I rinse the resin with hot about 50°C water to dissolve some copper tiosulphate which occurs on the resin. Finally I took it up with thiourea in acid. It has the mayor part of cations such as silver and gold and some impurities of iron and copper. I recognize them with basic analitical methods.

As I know the thiourea is such a strong complex so it isn't easy to operate with it. It didn't precipitate AgCl in ph >1.

1. Could it precipitate platinum with NH4Cl?
2. Could it precipitate palladium with DMG?
3. Could it later precipitate gold with oxalic acid (100°C)? (I know that silver oxalate is dangerous, but I will control the temperature)
4. Finally I think I could take the rest of silver and impurities with NaOH and to reuse the solution adjust the pH to 3 using HCl.

I need help and thank you in advance.

 

[jimdoc]

Did you mean Thiourea?

 

[domus1212]

Did you mean Thiourea?

Yes, sorry, just corrected

 

[Lou]

Why don't you just plate the gold out of the solution?

 

[domus1212]

What do you mean?

I want to have a stabile method to extract noble metals from the solution under this conditions.

Lou do you know something more about the resins? I send you dm cause I found you knew something. I want to ask about color change. It went sandy color and now after naoh treatment it is gray and also some are whity-red granules. It it normal? If you know something about them write me dm.

Thanks

 

[Geo]

I believe you have to acidify the solution with HCl before the SMB will work. Personally, I would acidify and drop the gold with ferrous sulfate. Then cement the Pd on copper or steel wool.

 

[Lou]

It can be electronwon onto steel wool.

 

[Liquidau]

I believe you have to acidify the solution with HCl before the SMB will work. Personally, I would acidify and drop the gold with ferrous sulfate. Then cement the Pd on copper or steel wool.

Geo, what if there’s also copper and silver in there? Does Thiourea dissolve those too?

 

[Geo]

Geo, what if there’s also copper and silver in there? Does Thiourea dissolve those too?

Thio will dissolve silver, and copper if it's oxygenated.

 

[Liquidau]

Thio will dissolve silver, and copper if it's oxygenated.

So should ferrous sulphate or SMB be used first for gold, then DMG for palladium, then selective cémentation, or add HCl or salt to precipitate silver? What’s the best order in which to do it all?

 

[Geo]

Do you suspect all of that in your solution? What was the starting material? Thio needs to be acidified. Adding HCl will bring down any silver as silver chloride. If silver is in the mix, drop it first. If the solution tests positive for Au and Pd, drop the Pd first as SMB can drop some Pd. The gold will be last.

 

[Liquidau]

Do you suspect all of that in your solution? What was the starting material? Thio needs to be acidified. Adding HCl will bring down any silver as silver chloride. If silver is in the mix, drop it first. If the solution tests positive for Au and Pd, drop the Pd first as SMB can drop some Pd. The gold will be last.

I started with some cleaned black sand which came from incinerated, ground, sieved, and magnetically separated chips. Showed silver, copper and gold on a cheap XRF machine, but I suspect palladium as well. Added a couple of fingers as well and a broken up 486. Also added a few gold plated machine parts which seemed to strip everything pretty well. Then the zinc dropped some black powder.
I’m repeating the process but this time more methodically and precisely. The formula calls for ferric +3 ions, which might not have been there before.
I assume that Stannous works well here, as long as the solution is acidified?

 

[VK3NHL]

I started with some cleaned black sand which came from incinerated, ground, sieved, and magnetically separated chips. Showed silver, copper and gold on a cheap XRF machine, but I suspect palladium as well. Added a couple of fingers as well and a broken up 486. Also added a few gold plated machine parts which seemed to strip everything pretty well. Then the zinc dropped some black powder.
I’m repeating the process but this time more methodically and precisely. The formula calls for ferric +3 ions, which might not have been there before.
I assume that Stannous works well here, as long as the solution is acidified?

“Cheap XRF machine”
Pray tell us more

 

[Liquidau]

Sorry, that’s a bit of an exaggeration…it’s a Chinese desktop device the size of a toaster oven, and cost the lab US$5,000 (versus a typical American handheld gun device at $15K or a standalone machine the size of a small car at $100K). It is good for One decimal analysis of homogeneous samples, to detect 2 or 3 key elements….