Processing waste for PMs

Gold Refining Forum

Help Support Gold Refining Forum:

Rreyes097

Well-known member
Supporting Member
Joined
Mar 30, 2016
Messages
463
Location
Northern California
I didn't go with the sulphuric acid route. Do to safety concerns. As well as I didn't have any of it left. So I just put in 2ml of nitric acid with heat. As it warmed I eventually added 2-3 more ml of nitric. Kept warm. Then I tested with stannous and this is the result. After a few minutes. I'm not sure if it's clear enough but there was some darkening. As well as some reddish coloring but that since went away. What y'all think? Yes there is pms'? The other picture is of the waste material in a 1000ml beaker.
 

Attachments

  • 16692501075402917475409683428641.jpg
    16692501075402917475409683428641.jpg
    1.8 MB · Views: 0
  • 16692504520634482631666891921465.jpg
    16692504520634482631666891921465.jpg
    1.3 MB · Views: 0

Yggdrasil

Moderator
Staff member
Supporting Member
Moderator
Joined
Oct 30, 2015
Messages
2,692
Location
Norway
I didn't go with the sulphuric acid route. Do to safety concerns. As well as I didn't have any of it left. So I just put in 2ml of nitric acid with heat. As it warmed I eventually added 2-3 more ml of nitric. Kept warm. Then I tested with stannous and this is the result. After a few minutes. I'm not sure if it's clear enough but there was some darkening. As well as some reddish coloring but that since went away. What y'all think? Yes there is pms'? The other picture is of the waste material in a 1000ml beaker.
Hard to see from pictures.
Maybe maybe not, is all the sludge dissolved?

If not, siphon off the liquid and set it aside.
Then add a bit of HCl (forming AR) to the sludge and dissolve it, test it.
If positive for Gold, Precipitate it.

Keep the liquids as a start for a new Stock pot.
 

Rreyes097

Well-known member
Supporting Member
Joined
Mar 30, 2016
Messages
463
Location
Northern California
Sludge hasn't dissolved yet even after 2 hot HCl rinses. I also have approximately 6-8ml of nitric acid and the stannous thus far remains negative. So do you think it merits more nitric? In order for it to become aqua regia? I mean is there a certain percentage or amount it needs to become actually aqua regia? Or maybe another HCl rinse?
 

Yggdrasil

Moderator
Staff member
Supporting Member
Moderator
Joined
Oct 30, 2015
Messages
2,692
Location
Norway
No more Nitric I think.
8 ml Nitric will dissolve a significant amount.
Have you heated it?

So if it don't dissolve in HCl + 8ml Nitric I think you need to dry it and roast it.

Any amount of Nitric in HCl, will be AR in our perspective of it.
We use the Nitric as a booster/oxidizer for the HCl.
 

orvi

Well-known member
Supporting Member
Joined
Apr 13, 2021
Messages
1,242
Location
EU
I have experience with black sludge formed upon copper cementation of spent AR liquids from gold refining. And surprisingly, in black powders, no PGMs were to be found. It does not surprised me that there is no PGMs in the liquid - but it does surprise me why there is anything cementing. After XRF analysis, I found that black powder is likely to be mixed oxide powder, mainly some copper present... It was relatively heavy tho.. Never done any experiments with it and toss it into the waste...
 

Rreyes097

Well-known member
Supporting Member
Joined
Mar 30, 2016
Messages
463
Location
Northern California
Yeah every since the first stannous test that may or may not have had any positive findings. I know the nitric acid that I added was quite a bit. But I have no intention of adding more. Perhaps there simply isn't any pms cemented into the sludge? Very well could be the case no? And yes my friend I have heated. Via hot plate. But with all that sludge at the bottom I feel that it sometimes makes things too hot and I'm trying to not have glass shatter, because although it's one of my few remaining actual lab glass that could most likely take the heat. I rather not test it's limits. 🔥😵 Plus I just bought that 1000 ml beaker!
 

Yggdrasil

Moderator
Staff member
Supporting Member
Moderator
Joined
Oct 30, 2015
Messages
2,692
Location
Norway
Yeah every since the first stannous test that may or may not have had any positive findings. I know the nitric acid that I added was quite a bit. But I have no intention of adding more. Perhaps there simply isn't any pms cemented into the sludge? Very well could be the case no? And yes my friend I have heated. Via hot plate. But with all that sludge at the bottom I feel that it sometimes makes things too hot and I'm trying to not have glass shatter, because although it's one of my few remaining actual lab glass that could most likely take the heat. I rather not test it's limits. 🔥😵 Plus I just bought that 1000 ml beaker!
So do as told then, siphon off the liquid and pot it in the new stock pot.
Dry and roast the sludge for later processing.
 
Top