Electrochemistry Copper electrorefining question

[RikkiRicardo]

Hi i was doing some searches and i found the it almost is regards this topic this is how the big boys are doing it.
very interesting.


RikkiRicardo

 

[goldsilverpro]

Thanks. Good article.

 

[solar_plasma]

I wonder how far the operator's project has grown, since we do not see any new posts. If it just would be that easy, everyone in the forum would be a millionaire.

 

[witekprytek]

The cathode plays no real role in which metal would be deposited.

Well, that's actually not true. The phenomena is called "overpotential" and it comes in variety of different flavors (read: reasons/sources).
The potential at which plating begins depends on many factors like:
- particular ion density
- presence of concurrent ions
- temperature
- pressure
- material of anode/cathode

If you imagine a cell filled with pure solution of CuSO₄ and equipped with one Cu anode and two cathodes (of identical dimensions and identical distance from anode) - one made of Cu and one made of SS then
- Cu would more likely or in more volume deposit on Cu cathode until SS cathode is covered by Cu deposit at which point deposition would be equal
- while SS is still bare, you can lower voltage to a point when deposition would occur only on Cu cathode


Bear in mind that the electrode potential we so often look up in a table is for a reason called standard electrode potential.
for metals and their ions It is usually measured using "standard hydrogen electrode" (SHE) connected to negative terminal and electrode made out of measured metal connected to positive terminal. The cell is filled with solution of that metals salt at concentration of 1 mol/dm3. Measurement commences at 25 DegC, 1 atm pressure.

You change anything in that set and the potential will change as well. It wont be standard anymore.

Regards

 

[artart47]

Hi friends!
Just something that is on my mind! everything I've read on our forum concearning refining copper electricly has to do with a cell with solid metal being dissolved and plated out. I know very little about this and don't want to sound ignorant on the subject, but thinking outside-the-box, I woundered what happens if you set up a cell with molten metal. could impurities in copper be plated out of the alloy?
A google search. There seems to be a lot of research being done. I just have time now to read one thing, called "Molten Oxide Electroysis For Lunar Oxygen Generation Using In-situ Resources" Jim Evans Honorary Symposium.
I just thought it might be an avenue that could be explored. Per-haps there could be some answers there to our dilema?
artart47

 

[g_axelsson]

Well, that's actually not true. The phenomena is called "overpotential" and it comes in variety of different flavors (read: reasons/sources).
The potential at which plating begins depends on many factors like:
- particular ion density
- presence of concurrent ions
- temperature
- pressure
- material of anode/cathode

If you imagine a cell filled with pure solution of CuSO₄ and equipped with one Cu anode and two cathodes (of identical dimensions and identical distance from anode) - one made of Cu and one made of SS then
- Cu would more likely or in more volume deposit on Cu cathode until SS cathode is covered by Cu deposit at which point deposition would be equal
- while SS is still bare, you can lower voltage to a point when deposition would occur only on Cu cathode

I've known that the voltage is dependant of those factors and made some feeble tries to understand the math behind. Any chans that you might explain how to calculate the electrode potential?

Göran

 

[witekprytek]

Hi,
you can't really calculate the potentials. You would need to find table of potentials for each specific cathode or find it experimentally.
I said "really" because 20 years ago it wasn't possible at all, but today, with quantum physics progress it could be possible. Even if that's true it would involve LOTS of quantum physics knowledge and calculations, so realistically - not possible


As supplement to previous example there is another one:
- take NiChrome wire
- dissolve in hydrochloric acid
- place dissolved salts in the cell
- place two cathodes, one made of Ni and another made of Cr, and one anode between them at correct distance
- make sure you have good mixing of the electrolyte while plating

Now, it is theoretically possible to selective electroplate Ni on Ni cathode and Cr on Cr cathode.
In order to achieve that you would need to find overpotentials of Ni on Cr cathode and Cr on Ni cathode.
Then find what voltage at which salt concentrations would allow plating Ni on Ni cathode but would't allow plating Cr on Ni cathode.
Make sure the voltage does the same to Cr on Cr and Ni cathodes.
Adjust concentrations by adding Ni and/or Cr salts.
Turn on the cell and monitor concentrations by adding Cr or Ni salts when their relative concentrations falls out of brackets you calculate earlier.

If you do it correctly you would have all Cr plated on Cr cathode and all Ni plated on Ni cathode.


As you can see from level of complications it is rather theoretical possibility

Regards