Gold will not drop with SMB or Sulfamic Acid

[Rhpos]

Sometimes I'd just zinc everything out, rinse the residue, then heat lowly dilute PURE hn03 to selectively dissolve away undesirables ag pd pb sn

 

[Ag and Au]

Can you further explain this "then heat lowly dilute PURE hn03". Thank you.

 

[Martijn]

I think he means heat slowly in hot and diluted, thus not pure, HNO3.
But the 'rinse the residue' part is very important, or you will dissolve some gold. All HCl has to be gone.

 

[Ag and Au]

I slowly added zinc powder to the solution several weeks ago and had a series of controlled reactions. The reactions have subsided and I am left with a black, tar-like "paste" in my beaker. What rinse are you referring to? Distilled water?

 

[Martijn]

Here is exactly what I did to create this solution:
1) I added ~ 2-3 pounds of industrial grade circuit boards with high visable gold content (from the early 2000's) to the AP solution
2) Let sit for ~ 10 days with occasional stirring
3) Filtered out all of the solids (lots and lots of electronic components came off the boards)
4) Retained quite a "pile" of gold flakes/foils (and dark powder) in my filter
5) Dried out this pile
6) Added it to the Shor AR solution; all of it dissolved withing 1 - 2 hours, leaving a golden solution and a smile on my face
7) Added urea (no real fizzing observed), then used the Shor Quadratic precipitant and heated it.
8) Waited about 2 hours - no gold drop
9) Added SMB and heated to about 80 degrees C for about 1 hour - no gold drop.
10) Stannous test: instant dark brown and NO purple and a small trace of "white/silver".
11) Added some clean copper pieces - some residue dropped to the bottom of the beaker (didn't look like gold mud)
12) Added some sulfamic acid and heated then added more SMB - No gold drop.

My head is spinning and I am sure yours is too. I normally do not approach such processes like a "bull in a china shop" but this
one got away from me. My suspicions lie in the use of the Shor International products, as I have had dubious results in the past on much simpler, refining trials.

The high visible gold was probably an ENIG layer, if it was in between components.
Thick gold plating will have no purpose there, there is no contact point that can wear down, so why would a manufacturer waste gold on places it has no function other than corrosion resistance.

This ENIG plating is so thin, it disappears when you try to refine it.
As other said, I think your gold is/was in the flask, the solution looks to be holding suspended dust. And it may not be enough to collect and melt.

Next time, try to weigh those foils and be shocked by the lack of weight.

Did you weigh the small pile before AR?

Cemented gold looks more black to dark brown than a golden color or the light brown from washed pure gold powder. That bit of residue probably is your gold. Keep the copper in longer. Agitate a bit evey now and then or use an air bubbler. Stop when clean copper stays clean after a few days.

And yes, Shore is not very popular here.
What i always say: if the manual is not clear, or the manufacturer can't help you, don't use the product.
Did you ask shore for help?

If the amount is too small to melt, you could make a reference liquid with it to test your stannous.

You say you usually don't do it like this, have you dropped gold with SMB before or have you used this shor product before with succes?

Martijn.

Edited for correct spelling.

 

[Martijn]

I slowly added zinc powder to the solution several weeks ago and had a series of controlled reactions. The reactions have subsided and I am left with a black, tar-like "paste" in my beaker. What rinse are you referring to? Distilled water?

Lots of boiling distilled water rinses to get all chlorine out to avoid creating weak AR, with the risk of dissolving some gold again.
But i suspect you don't have nitric since you use the other thing.

What i forgot to add to my previous post:
https://goldrefiningforum.com/threads/when-in-doubt-cement-it-out.30236/

 

[Ag and Au]

Martijn: Thanks for the ENIG information and the rinsing information. I learn fast, so keep the info coming....As to your first question, I did not weigh the small pile before AR (but I will in the future).

Regarding your, "Cemented gold looks more black to dark brown" statement... I conducted a completely separate, smaller AP experiment and I successfully cemented the gold out (and yes, it did look more black than brown). I learned that I added too much H2O2 at that time. I took the black power and filtered it and rinsed it with HCL. Then I made a small amount of AR using the Shor International MX-3 Nitric substitute (plus HCL) and dissolved it in that beaker. Filtered it then added sulfamic acid (heated) then filtered it again. The solution was magnificently clear and bright green (pictures attached). Stannous test was purple. I added SMB this morning....I will check it tonight.

Shor International has a nice video and convinced me to begin with a safer alternative to Nitric. They have a product called MX-3 (nitric substitute) which seemed to work fine as an AR (mixed with diluted HCL). Then they recommended using UREA to denox then to use their version of SMB (called Quadratic Precipitant). Naturally several filter processes were involved in between steps. The jury is still out in my mind on their products. Their tech support was helpful, but nothing even close to this forum.

Regarding this question: You say you usually don't do it like this, have you dropped gold with SBM before or have you used this shor product before with success? I don't have a clear answer for you on this question yet (see picture #3).

 

[Martijn]

I would say your gold has dropped in picture 3. Let it settle for a couple of days and decant in the stockpot after a negative stannous test. If it does not settle, heat it with a couple ml's of sulfuric acid and it will clear up the solution, letting all gold dust settle.

Forget urea, it's for the garden.

Do you premix the HCL / MX3?
You might be able to add small amounts to the HCl and keep track of how much grams of gold foils you can dissolve with a certain amount of MX3, so you don't need to get rid of excess nitric.