Oops, thiolsulphate leaching mistake!

[aussie_noob]

Mistakes were made.

Used thiolsulphate to leach gold plated pins, got a clear solution.
Then added hcl to get to a ph of 3-4 and added smb. And then realised smb doesn't work with thiolsulphate.
The solution turned a yellow murky colour, i suspect the ph caused the thiolsuphate to degrade, fine gold in solution, no longer dissolved.
Dunno how to get the gold now?
High salt from both HCL and NaOH that were added to adjust ph, can't tell ph from high salt.

 

[Yggdrasil]

Mistakes were made.

Used thiolsulphate to leach gold plated pins, got a clear solution.
Then added hcl to get to a ph of 3-4 and added smb. And then realised smb doesn't work with thiolsulphate.
The solution turned a yellow murky colour, i suspect the ph caused the thiolsuphate to degrade, fine gold in solution, no longer dissolved.
Dunno how to get the gold now?
High salt from both HCL and NaOH that were added to adjust ph, can't tell ph from high salt.

Well HCl and NaOH gives NaCl(Table Salt).
Salt is neutral and should not affect the pH to much I believe.

I'm not sure if SMB works with ThioSulfate or not, but it should be more in the range of 2-1 for best effect.
If the Gold are in particle form just add HCl and a little bit of Bleach and it will redissolve
and you can use SMB, Copperas, Ascorbic or what ever your preferences are.

What you do NOT do is start throwing chemicals at it in hope something works.
Ask first.

 

[aussie_noob]

What would happen if you just evaporate to a powder and furnace it? Dumb idea?

 

[Yggdrasil]

What would happen if you just evaporate to a powder and furnace it? Dumb idea?

One of the reasons ThioSulfate is not much used is that it is hard to get the Gold out.
Smelting might be a solution but might be riddled with heavy losses.
Not sure here, but smelting/decomposing salts always poses risks of losses.

The best bet is always to use the most common methods, they are most common for good reasons.

 

[nickvc]

Another idea is to use the charmin plug basically a toilet paper plug in a funnel , pour your solution through it and it should catch your fine gold particles if you still see particles in the solution you may need to do it again , rinse thoroughly with water , recover the plug and dissolve your gold using Hcl and bleach or HCl and peroxide , filter and precipitate your gold .

 

[Yggdrasil]

Another idea is to use the charmin plug basically a toilet paper plug in a funnel , pour your solution through it and it should catch your fine gold particles if you still see particles in the solution you may need to do it again , rinse thoroughly with water , recover the plug and dissolve your gold using Hcl and bleach or HCl and peroxide , filter and precipitate your gold .

Maybe I misunderstood. I thought it still was in solution?

 

[aussie_noob]

Tried adding hcl, went from clear, to murky yellow over a minute, then to orange and then dark orange / brown over minutes.

Think this is fine gold? It may look different to smb precipitated gold as smb grows larger gold particles, in this case it could be very fine.
After letting it settle for 20 minutes a brown layer is forming on the bottom with an orange brown murky solution. I'll estimate 10g gold should be in the beaker, just dunno if this is it in solid form or something else?

 

[Yggdrasil]

Tried adding hcl, went from clear, to murky yellow over a minute, then to orange and then dark orange / brown over minutes.

Think this is fine gold? It may look different to smb precipitated gold as smb grows larger gold particles, in this case it could be very fine.
After letting it settle for 20 minutes a brown layer is forming on the bottom with an orange brown murky solution. I'll estimate 10g gold should be in the beaker, just dunno if this is it in solid form or something else?

Did you find a procedure about this or did you just do it?
And no it is not Gold just by its color, to me it looks more like Iron.
Concentrated dissolved Gold in chloride form, looks vaguely similar in color, although a bit more on the reddish side.
Precipitated Gold has the same color independent of the precipitant, the only factors influencing this is purity and particle size.

 

[anachronism]

Tried adding hcl, went from clear, to murky yellow over a minute, then to orange and then dark orange / brown over minutes.

Think this is fine gold? It may look different to smb precipitated gold as smb grows larger gold particles, in this case it could be very fine.
After letting it settle for 20 minutes a brown layer is forming on the bottom with an orange brown murky solution. I'll estimate 10g gold should be in the beaker, just dunno if this is it in solid form or something else?

One way to find out. Filter that solution and dissolve a sample in regular AR or HCl/bleach and see if you get a positive stannous test.

In fairness it does look like fine gold powder at the bottom but this way you get to test and see.

 

[anachronism]

Did you find a procedure about this or did you just do it?
And no it is not Gold just by its color, to me it looks more like Iron.
Concentrated dissolved Gold in chloride form, looks vaguely similar in color, although a bit more on the reddish side.
Precipitated Gold has the same color independent of the precipitant, the only factors influencing this is purity and particle size.

I disagree Ygg. The powder does look like Gold, but if he tests as I suggested we will know. Wouldn't be the first time I've been wrong of course mate. Haha,

 

[aussie_noob]

There's some smart people here, can figure this out without physical tests. I will do them though, preparing stannous and other tests, but want to learn. Brain excercise. Imaginary trophy for the one who gets it right.

Composition of pins:

copper, zinc, silver, lead, gold by xray analysis. Mostly copper. No iron. Estimated 10g gold in the beaker sample based on number of gold plated pins.

Steps/observations:

1. Thiolsulfate leached the gold, possibly other metals leached too? Multiple days leaching with air bubbling, so maybe?
2. Added HCl to lower ph, panicked when metals fell out, murky solution.
3. Added NaOH to redisolve, went clear over days.
4. Added HCl again.
Initial change to murky yellow, then after minutes a possible secondary slower reaction occurred? Fine brown particles fell out.
Dense yellow on bottom, fine brown settled over hours.
20mL bottom yellow layer, 100mL brown layer. Clear solution at top.

What are the yellow and brown particles?

 

[anachronism]

My gut feeling is that you've dropped everything out.

 

[aussie_noob]

My gut feeling is that you've dropped everything out.

Yes I have dropped everything out. HCl low pH makes thiolsulphate drop everything.... I want to know what is dropped?
A different question with the same answer is, what do you think the thiolsulphate leached from the pins? How much copper, tin, lead vs gold? It likes gold, but there was a good 2 days of leaching with mostly exposed pins, little gold plating left.

Also, this isn't smb drop. Smb = big particles, denser gold sediment. Approx 1mL gold sediment expected.
Acid dropping from thiolsulphate = smaller particles, much less dense. Could have 10x to 100x more gold sediment volume.

Ummm, is it all gold? Is thiolsulfate that good of a selective leach? Sounds plausible based on the volumes observed.

 

[Yggdrasil]

There's some smart people here, can figure this out without physical tests. I will do them though, preparing stannous and other tests, but want to learn. Brain excercise. Imaginary trophy for the one who gets it right.

Composition of pins:

copper, zinc, silver, lead, gold by xray analysis. Mostly copper. No iron. Estimated 10g gold in the beaker sample based on number of gold plated pins.

Steps/observations:

1. Thiolsulfate leached the gold, possibly other metals leached too? Multiple days leaching with air bubbling, so maybe?
2. Added HCl to lower ph, panicked when metals fell out, murky solution.
3. Added NaOH to redisolve, went clear over days.
4. Added HCl again.
Initial change to murky yellow, then after minutes a possible secondary slower reaction occurred? Fine brown particles fell out.
Dense yellow on bottom, fine brown settled over hours.
20mL bottom yellow layer, 100mL brown layer. Clear solution at top.

What are the yellow and brown particles?
View attachment 65119

Hmm.
Jon is probably right.
How much pins did you dissolve?
10Kg, 1Kg ?
10grams of Gold would points to the first, depending the quality of the pins.

I do not like the way you operate,
adding chemicals without a clear knowledge of what is expected and then adding something else when things do not go as expected.

Formulate a clear plan, with what is expected and then have us review the plan then follow it.
If something do not go as expected, check it and review again before pushing on.