Regening AP - am I doing it right?

[Wingedcloud]

Hello everyone,

I recently used an AP solution to get gold from RAM fingers. When I started the fingers batch, it was already a used brown AP solution, so it already had a high concentration of Cu+ ions in it. Since I didnt want to start a new AP solution just for the fingers, I used the old one and managed to get all the fingers done. I was careful to add small quantities of HCl here and there to keep the solution going, while always having the air pump on too.
After I was done, I moved the solution to a new container to keep it stored and kept the bubbling going. I read that to optimize your AP solution, one should keep it aerated between batches, to promote the regening of the solution, turning Cu+ ions into Cu2+ ions.
It's been 2 weeks or so since I finished the fingers batches, and despite being aerated, the solution color didn't changed much.
My question is this: since it was so saturated in Cu+ ions, I should keep the solution on "standby" for longer, or is it already beyond any possible recovery?

I started a new batch today with some material I have collected, but, for this one, for 2000 mL of AP, I used 800 mL of old AP solution and the remaining (1200 mL) of fresh HCl. Is there a better/appropriate ratio to use in this cases or is it just a matter of gaining experience while working?

Thanks in advance for any help provided.

Kind regards,
Winged

 

[Geo]

Take a small sample in a glass container. Note the amount. Add fresh HCl until the solution goes back to green. This will give you an idea of how much HCl you need to add to reactivate the solution.

 

[jason_recliner]

As long as there is copper still in a solid form, AP will find its own equilibrium.

You could add a lot of HCl (or H2O2) and have it appear green, only for it to then turn to black rather quickly. The very action of dissolving copper will keep it turning toward dark brown/black. Oxygen will keep it turning towards green, but this allows it to dissolve copper more quickly, thus causing it to trend to black. There's your equilibrium. This is why it tends to stay brown/black until it's finished, then rapidly go green at the end when aeration rate exceeds the copper dissolution rate.

If you have white or brown crystals appearing on the bottom, only then are you definitely short on HCl.

You might want to consider your bubbler. If you have a very deep container, an open ended hose may be enough for good absorption in the long rise time, and I know Geo does nicely with that. Otherwise a $2 aquarium stone might give better absorption of O2 through thousands of tiny bubbles instead of a few large ones. I saw a huge difference adding a stone: 2 months became 1 week.

 

[solar_plasma]

You need to add as much HCl as has been consumed. Afterall I feel it to be somewhat misleading, to call it regeneration. If it were a kind of regenerating there would not come more and more volume. Using electricity would be closer to an example of regeneration - without saying that this would be practical.

Understand the CuCl/CuCl2-system with air supply as a catalyst, that makes it possible for the HCl to do its work and while it does its work, it is producing more of the catalyst until all HCl is spend.

So to answer your question from my point of view: You can almost not do it wrong. As well you could just take new HCl and only add a small portion of old leach, it doesn't matter that much.

 

[jason_recliner]

You need to add as much HCl as has been consumed

Plus as much is required for the batch, minus the amount you started with. 8)

 

[solar_plasma]

You need to add as much HCl as has been consumed

Plus as much is required for the batch, minus the amount you started with. 8)

:mrgreen:
I can't deny this, I counted that under consumption in a wider meaning.

 

[Wingedcloud]

You could add a lot of HCl (or H2O2) and have it appear green, only for it to then turn to black rather quickly.

That was spot on, sir. After just one day on this batch, the solution is close to the color of the old one I previously used, but the free HCl still available is doing it's work
One teacher of mine used to say "Systems always find their equilibrium point". I guess he was right and it applies to this also

If you have white or brown crystals appearing on the bottom, only then are you definitely short on HCl.

A white salt used to appear during the washing of my last batches of fingers. When I washed my basket with water, a white salt formed, joining the washed fingers, which I dissolved, by rinsing the filter with HCl when I was filtering the gold fingers. I've read that when a saturated copper solution is very diluted, the copper precipitates as copper hydroxide, so I recognized it as soon as it happened.

The process is running smoothly now. Today I put new material to be processed, which will be done by tomorrow.

If I may, I would like to ask something else: some of the material I want to process has some solder on it, so I run it on a beaker with a 2:1 water/HCl solution to remove solder. However, after little time, the places where the gold is start to become black and a black powder forms. I filtered all of this black powder, in case it contains some gold. Do you think it's possible that some of the gold dissolves in the HCl and cements back out as this black powder? I know gold shouldn't dissolve in HCl alone, but I don't have any explanation for this black powder appearing :/

Thank you all for your help.

Kind regards,
Winged

 

[kernels]

I had the same issue when I boiled the HCl solution to get rid of solder (you don't have to boil it!) , didn't seem to be as much of a problem when I just gently heated the HCl.

 

[g_axelsson]

Adding water to a concentrated CuCl solution in HCl dilutes the HCl to the point where CuCl starts to precipitate. The white precipitate formed is solid CuCl and is easily dissolved by adding more HCl.

Gold is not dissolved and cemented back when you are removing tin with HCl. Gold is dissolved in the molten tin at the time the card is soldered so any gold in the tin will be freed and settle as a fine black sludge. The amount is very little so it can be hard to see it among other insoluble parts as tin or lead oxides.
I'm not sure what the black surface is made up of, but my guess is that it can be a mixture of metallic alloys of copper, nickel, lead, tin, silver and gold. All metals that can be present in the solder. A surface that is very rough on a microscopic level could easily turn black even if the metal involved isn't black in larger pieces, just compare to the fine black gold powder dropped from a dirty solution.

Göran

 

[Topher_osAUrus]

The black could be the other constituent elements of the solder. Like antimony maybe?
Or in the old solder i used to make my stannous i had black residues and it was a tin/silver solder.
It could be gold though, if you used alot of heat for an extended amount of time.

Hard saying though, as there are alot of variables.

Edit: Görans post = better

 

[Wingedcloud]

Adding water to a concentrated CuCl solution in HCl dilutes the HCl to the point where CuCl starts to precipitate. The white precipitate formed is solid CuCl and is easily dissolved by adding more HCl.

Gold is not dissolved and cemented back when you are removing tin with HCl. Gold is dissolved in the molten tin at the time the card is soldered so any gold in the tin will be freed and settle as a fine black sludge. The amount is very little so it can be hard to see it among other insoluble parts as tin or lead oxides.
I'm not sure what the black surface is made up of, but my guess is that it can be a mixture of metallic alloys of copper, nickel, lead, tin, silver and gold. All metals that can be present in the solder. A surface that is very rough on a microscopic level could easily turn black even if the metal involved isn't black in larger pieces, just compare to the fine black gold powder dropped from a dirty solution.

Göran

Thank you Göran for your reply.
You're most likely correct stating that "it can be a mixture of metallic alloys of copper, nickel, lead, tin, silver and gold". I left the filter wide open to dry overnight, and this morning it presents a dark...green color on some parts. So, following your advice of comparing with the color of the fine gold powder I usually get from my refinings, it has nothing to do with it. However, I'm not discarding the possibility of it having a bit of gold in there, so I'll just save the filter among others I have to get them handled some time later and maybe get myself a nice gift ^^

It could be gold though, if you used alot of heat for an extended amount of time.

I don't find that possible because I don't apply heat to my AP method.
Thanks for your reply though

Kind regards,
Winged