How to get rid of CuCl in AP solution?

[Marcel]

Reading trough this forum,I realized that AP could be reused.I never did that before, so I wanted to give it a try. I started one process that took 1 day to get some gold from memory fingers and some flash-gold-plated boards.
I the seperated the remaining blueish AP Solution into 2 containers.
One I used to drop some CPUs in their and the other one I heated around 50°celsius and processed some PCI goldfingers with it.
Added only a few drops of H2O2 33%.
Both solutions started to work fine and removed BM agressively, then suddently both started to develop a milky- white floating substance on the bottom.
Now I researched, that it is most like to be SnCl, since their was quite some Silver involved in the first run, but also tin.
Now I wonder, how to get rid of this stuff? If you stir it the solution gets a bit clearer then milky again.
Is this SnCl? And how can I remove it? The reaction has come to a standstill btw. Only adding a bit H2O2 will restart it for a short while then stop again after some minutes.
The white stuff is not passing through my paperfilter, but the foils hang in their now too.. :-(
Both solutions are dark blue. Any help is appriciated

 

[Geo]

add a little fresh hcl to one batch and see if it clears up.

 

[Marcel]

No sir, no clearing up.
If my Hong Kong PH meter is correct PH is around 2.5. I placed a copper sheet into it and it was eaten all up within minutes, after I removed it from solution. Inside it could last and nothing would happen.

 

[butcher]

The white stuff sounds like lead or silver chloride,

Also from your description it sounds like you are using too strong of hydrogen peroxide,
3% H2O2, to get started, or regenerate, or air can also be bubbled in, the strong oxidizer will dissolve metals faster but can also give other problem's like dissolving the gold before you wish to do so.

 

[Lino1406]

The white material is tin dioxide (metastannic acid).
It dissolves in 60% H2SO4, which is viscous, or better hot alkali.

 

[Claudie]

A picture of what you are working with may help. I had a similar issue a while back. Does it look anything like the picture in this post? http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=10507&p=101548&hilit=Silver#p101548

 

[Geo]

i thought metastannic acid was created in nitric acid, it can be formed in hcl too?

 

[butcher]

Metastannic acid (H2SnO3) is not made in hydrochloric acid (HCl). It is made from dissolving tin (Sn) in Nitric acid (HNO3) or in aqua regia, which can also form a major nuisance; tin in nitric acid creates a gelatinous compound that gives us much trouble in our solutions, with filtering and reducing metals to colloids.

Tin dissolves in HCl, to form stannous chloride (SnCl2) this is usually a clear solution, it will also reduce metals in solution (like gold in solution reduced to a colloid violet color we use in testing gold bearing solutions), in HCl tin chlorides are also troublesome, filtering and reducing metals like copper iron and gold into colloidal form.

Tin chloride can also form Tin(IV)Chloride (SNCl4) in solutions of HCL if solutions are diluted, these are also more trouble to filter than the Tin(II)Chloride (SNCl2) (formed in concentrated HCL). Both of these are soluble in HCL and form gel, and reduce metals lower than tin in reactivity series many of these metals become colloids in this gelatinous solution, the elemental metal not precipitating as they normally would from a solution that did not include tin.

SNCl2 and SNCl4 are soluble in HCl solutions, and would be clear as long as it is not bonded with another metal as a salt colloid lingering barely dissolved in the solution as a gelatinous compound.

Tin (Sn) will dissolve in hydrochloric acid (HCl) and the action is accelerated with oxides such as hydrogen peroxide (H2O2).

Tin in our solutions is just a trap for our gold, tin steals your gold from you, it can dissolve gold with low heat when soldering or de-soldering, (locking up some dissolved gold in the solder), (so melting whole boards some gold is lost to the solder, unless it is processed. In solutions tin reduces our gold to metal this gold forms colloids, which will not precipitate, and cannot be tested for with our stannous chloride test, we can be throwing gold out in this solution with our waste.


Keep tin out of your solutions, not only is it a pain in that thing behind you but also you may just keep more of that gold your working so hard to get.

 

[Lino1406]

The stable form of Sn+4 in the presence of
water is SnO2. So, after you eliminate
possibility of AgCl, PbCl2, CuCl.. that what
remains.

 

[Marcel]

After filtering and having it settle over night, this is how my paperfilter looks right now:



Before filtering, the solutionw as deep green, after blue.
Stuff does not dissolve in HCL, H2O2 or H2O

@butcher: It´s here where I learned that 33% H2O2 is not the best way to process my material. Will reduce to 7% from now on and see how that works for me.

 

[Geo]

did you try hot water?

 

[Marcel]

Hot water helped! Thanks a lot...

 

[Geo]

its copper chloride. soluble in hot water. in my opinion.

 

[lazersteve]

The filter looks like it contains a gummy/gooey compound to me. I would guess it's some form of tin or another.

It's also possible that it could be an additive in one of his reagents.

Steve

 

[Geo]

i have noticed that the few times i have had AP solution on my hands (on bare skin) and tried to wash it off with bar soap, the soap would become gooey and sticky and more soap would not wash it off. i had to scrape the green colored soap off with a blade. could your solution have come in contact with soap?

 

[mirdahd]

Small pins I made ​​in 65% nitric acid.
Acids dissolve the copper component and only gold remains in solution kysliny.
Use but a lot of acid. There is no better electrolysis?

 

[Geo]

Small pins I made ​​in 65% nitric acid.
Acids dissolve the copper component and only gold remains in solution kysliny.
Use but a lot of acid. There is no better electrolysis?

search the forum for "gold stripping cell" or "gold cell" or "sulfuric stripping cell".