Black particles in with gold foils

[hammerdown]

Hey Forum!

I've been recovering foils from very close trimmed boards for a few years now (yet to process-refine though), but with the last few batches I've been noticing quite a bit of dark grey-to-black fine powder-like particles filtering out with the foils once removed & rinsed from the CuCl2 solution. It even clouds up in the clean beaker once rinsed off the filters. My acid is used, but has only been used on close fingered material with no solder, components or iron bits... and is still a good amount of emerald green colored, so I know it's not becoming Iron Chloride (no browning color to the solution). I would like it if it was just super fine gold from ENIGed fingers, but I can't fathom why it would cloud up a beaker of water if it was just gold powder. It will settle over night about 80-90%, but the water still remains murkyish transparent. I know it could possibly be nickel from the barrier between the gold and copper layers, but this didn't use to be a problem before. Any ideas? Could it by chance just be from organics (like bugs) that found it's way into the solution while being processed in CuCl2? I haven't yet evaporated the water to HCL wash of the foils until I get a better idea what the very dark fine material could be first.

How I go about it is...

1st - I pull up the small bucket containing the material from the CuCl2 solution and allow as much solution to drain out of the drilled drain holes as I can, while giving a few sprays of distilled water to rinse the sides & handle of the material bucket, back into the CUCl2 bigger bucket.

2nd - I place the material bucket into a clean empty bigger bucket to drench distilled water over the material to rinse off as much lingering CuCl2 as I can and let drain.

3rd - I take the remaining material bucket into my shop for the daunting task of removing the material while making sure all stuck, but loose, foils come off each finger into a clean catch container at a later time... which will also now end up with the powder-like material too.

4th - I filter the copper laced rinse water to recover the foils that fell through the drain holes during marial rinsing. That's when I start noticing the black power building up... also after I'm done with material in the shop.

5th - If I don't have other finger batches to run, I filter out the CuCl2 acid to reclaim the foils released during processing. This too will now leave black powder-like material on the filter.

 

[hammerdown]

Beaker pics

 

[FrugalRefiner]

If you've been using the same AP solution for a while, it could be gold that went into solution when you first started the AP, which has now cemented out as a very fine powder. If it's a base metal, it will be eliminated when you refine the gold.

Dave

 

[hammerdown]

If you've been using the same AP solution for a while, it could be gold that went into solution when you first started the AP, which has now cemented out as a very fine powder. If it's a base metal, it will be eliminated when you refine the gold.

Dave

It's nothing for the powder to also pass through the 1st layer of filter onto the 2nd layer in good amounts.

So it is safe to assume that I can proceed with vaping off the water and then HCL washing the foils? I assumed at first to go ahead with it, but wanted to reach out first to avoid any possible hiccups to have to work through later from anyone who may know from experience. Thanks Dave!

 

[hammerdown]

A thought of inquiry I just had...

Perhaps this has been answered before, but I couldn't locate the threads if so, but can gold break down into fine powder, or even be digested, if left in a CuCl2 solution too long that has an air pump constantly aerating the solution? What made me think of this is, I've learned from many posts over the years that adding H2O2 can dissolve gold into the AP / CuCl2 if too much or too frequent of adding more is used. That being said, wouldn't a long-term (couple weeks or more) of constant air pump aeration add too much oxygen that would in turn cause the same issue as too much/often H2O2 adding? I typically leave my batches in for 2-4 weeks before retrieval. Probably way longer than it needs to be, but I'm in no rush-rush hurry of inpatients when I do recovery, plus I have my job and other life duties I tend to as well. But regardless, is it possible or even probable?

 

[cosmetal]

"That being said, wouldn't a long-term (couple weeks or more) of constant air pump aeration add too much oxygen that would in turn cause the same issue as too much/often H2O2 adding?"

I don't have a direct answer to your question. But, I have read that the addition of too much "oxidizer" will cause the gold to dissolve into the AP solution. When saying "oxidizer", are "they" referring to H2O2 or a 24/7 air pump?

Good question.

My money is on the H2O2. If a 24/7 air pump also adds too much "oxidizer", you will have to check your solutions (repeatably :shock: ) with the SnCl test. If the test ever shows a positive result, you have found the tipping point and, also, your answer.

Peace and health,
James

 

[hammerdown]

"That being said, wouldn't a long-term (couple weeks or more) of constant air pump aeration add too much oxygen that would in turn cause the same issue as too much/often H2O2 adding?"

I don't have a direct answer to your question. But, I have read that the addition of too much "oxidizer" will cause the gold to dissolve into the AP solution. When saying "oxidizer", are "they" referring to H2O2 or a 24/7 air pump?

Good question.

My money is on the H2O2. If a 24/7 air pump also adds too much "oxidizer", you will have to check your solutions (repeatably :shock: ) with the SnCl test. If the test ever shows a positive result, you have found the tipping point and, also, your answer.

Peace and health,
James

Thanks for responding James!

What prompted my random ? thought earlier is my growing predicament with fine black powder-like with my foils and my extended use of an air pump during the recovery period. And, "oxidizer" "O2 in H2O2" and "oxygen" all being of seemingly obvious relation to one another prompted me wonder. I soooo would hate for that to be the case, though, since I prefer to just let my process do it's thing in the CuCl2 jacuzzi for a couple weeks, or longer, during the hot months in the sun, while I tend to other things that also keep me busy. Me and SnCl sooooo don't get along in trying to make it, but I will just have to find a way that will work, for me anyways, at some point so I can use it in it's multitude of needs in this urban mining hobby. I too am leaning towards it being just with H2O2 being an oxidizer culprit for gold in AP rather than just "air", but thought I'd ask in case anyone might know.

 

[Lino1406]

2Au + 8HCl + 3/2 O2 = 2HAuCl4 + 3H2O is thermodynamically favorable, meaning gold can be dissolved with oxygen instead of hydrogen peroxide

 

[nickvc]

When washing your precipitated gold powder in HCl some gold will dissolve just in the acid so add oxygen to that mix and yes some of your gold can dissolve but it should cement out as you add more product.

 

[hammerdown]

2Au + 8HCl + 3/2 O2 = 2HAuCl4 + 3H2O is thermodynamically favorable, meaning gold can be dissolved with oxygen instead of hydrogen peroxide

So, in layman's terms, continuous 24/7 aeration of CuCl2 with an air pump, pumping regular atmospheric "air" oxygen, will in fact actually do the same as if adding hydrogen peroxide as far as gold digestion?

 

[Lino1406]

That what was said. If the aim is stirring choose another option

 

[hammerdown]

From everyone's responses, I feel a bit more at ease that the dark particles I'm beginning to get are more than likely gold, if not cemented base metals that would get re-dissolved during HCL washing, and that I ought not worry about proceeding as normal in fear of foreign contaminates being problematic. And also that I ought not fret too much about leaving my material in the CuCl2 jacuzzi for extended periods. Thanks everyone!