When Is HCL Exhausted Trying To Dissolve Copper? Will It Get All Used Up?

[scrapparts]

Do anyone know how much HCL needed to dissolve approximately 20 lbs of silver contacts that are mostly copper in weight?

The reason I'm asking is that I have 4 pieces of silver contacts (approximately 4lbs+ each piece), I had them in a gallon and half of Muriatic Acid since Dec, 2020. Nothing is wrong, it's just that the weight of the container isn't any lighter, but the solution is dark as black, and the copper is dissolving, and the silver is getting more and more exposed to the solution.

I have an air bubbler going. I guess I'm asking is "Will the solution get too concentrated that it won't dissolve any more copper?"

Thanks in advance for any info.

scrapparts

 

[butcher]

Spend some time studying how the leach works, to gain a better understanding.

HCl is not what dissolves copper.
Oxygen is not what dissolves copper.

It is the cupric ion that we use in this leach to dissolve copper or other base metals.

In this leach, it is a cupric ion (CuCl2) or a salt of copper that becomes the oxidizing agent strong enough to take electrons from the copper metal atoms dissolving them into solution as copper ions.

HCl and an oxidizer ( air or 3% H2O2) will dissolve some copper into the solution forming a green cupric chloride solution CuCl2.

To dissolve a metal, we basically remove electrons from the shells of that metal's atoms, so that basically we make a salt of that metal dissolved in solution, in this case, copper ions.

Oxidize (to lose electrons) when we dissolve a metal we are taking electrons from the atoms of that metal, the metal missing electrons becomes an ionic salt of that metal.

Reduction (to gain electrons), when we precipitate a metal we give back electrons to the ions in solution forming atoms of that metal with a full shell of electrons, basically changing the ionic salt of that metal back into elemental metal (although in a powder form of that metal).

Before something can be oxidized something else has to be reduced. before one thing can be reduced something else has to be oxidized.


Basically, we are moving electrons, before we can take or give an electron, we have to have something to take or receive the electron...

So as our green cupric chloride CuCl2 oxidizes (or dissolves) the copper metal (taking the electrons from the copper), the cupric ion at the same time itself is being reduced (gaining those electrons) to become a dark brown solution of cuprous chloride CuCl, basically depleting its ability to dissolve or hold more copper, or less willing to take on more electrons...


Cupric chloride is the oxidizing agent for copper metal (CuCl2) the cupric chloride will take electrons from the copper metal), basically dissolving the metal into solution as a salt of that metal, and a salt of the former acid, or a soup of copper ions and chloride ions. as the green solution becomes saturated with copper ions its power as an oxidizing agent is depleted and the solution becomes a darker brown as the solution becomes more of cuprous chloride (CuCl) solution less able to dissolve copper (under these atmospheric conditions), and as the valence of these copper ions change you may see white powders of copper I Chloride CuCl precipitate.

To regenerate the leach, convert the dark brown cuprous chloride back into a bright green copper hungry solution or back into cupric chloride, we add a splash of HCl and bubble in some air to provide some oxygen to the solution...

Silver builds a protective crust in acidic chloride solutions, the outer layer forming a salt of the metal and acid which keep the underlying metal protected from the action of the acids, aggressive agitation can break loose some of the crust to form another layer of salt.

With what you are doing here you are likely to have silver in two forms as elemental metal alloy and as a salt of silver or silver chloride...
I would also take into consideration with this and contact points, that some palladium could also be oxidized by the cupric solution.

 

[nickton]

When you regenerate does some of the copper drop, or get somehow removed or filtered out? Eventually there must be so much copper salt (and some other base metals) in solution that it has to go somewhere does it not?

I have been distilling my spent cupric chloride material to get clear hydrochloric acid, which is nice to have, but now I wonder if it's necessary. I also have a pot of what it leaves behind after distillation, that I'd like to turn back into copper.

 

[butcher]

When you regenerate does some of the copper drop, or get somehow removed or filtered out? Eventually, there must be so much copper salt (and some other base metals) in a solution that it has to go somewhere does it not?

The copper stays in solution as greenish CuCl2 cupric chloride, as the solution gets saturated with copper and the oxidation state, or ORP (oxidation-reduction potential) of the solution changes, the saturated copper may begin to precipitate some copper as a white powder, along with a change in Orp some other base metals may begin to precipitate as oxides or hydroxides if the pH is changed. some metals like silver, lead, and mercury is insoluble as chlorides and will also be in the insoluble salt form...
So basically copper and base metal for the most part stay in solution.

I have been distilling my spent cupric chloride material to get clear hydrochloric acid, which is nice to have, but now I wonder if it's necessary. I also have a pot of what it leaves behind after distillation, that I'd like to turn back into copper.

With the cheap price of HCl and the easy availability, I cannot see that it is worth it unless it is just a bonus of treating the waste or for some other purpose.
Although if you are distilling off HCl from the copper chloride solution, adding H2SO4 would help to drive off the chlorine gases and convert the copper to a useful copper sulfate...