[pifi]

Deleted. valid is post below

[pifi]

Hello,
please help me understand electrolysis metal separation where pure metal is made. I am interested in known metals Cu, Ni, Zn, Sn, Pb, Ag .
I know basic process, where electrolysis is used to clear copper alloy electrode (impure electrode) to pure copper, and dissolved dust of other metals. There is known "clear" electrolyte used.

(?) What I didn't know - If I can apply same process for removing specified Kation (Cu+,Ni+, ...) out of the electrolyte.  (i.e. I have mixture of CuCl2, NiCl2, ...) to get out firstly copper, then nickel, ... .

Thanks,
L.

[Arkcon]

Hi there, pifi:, I've gone and merged two similar questions of yours into one thread.  Its more useful to posters on these forums if all your thoughts and ideas are in one place when they answer.

[EDIT]  Well there was something people could have used, before you deleted it.

Here's an online resource on the electrorefining of copper: https://www.ausetute.com.au/electrorefine.html  And you may be able to find more.

By some mechanism that I don't fully understand myself, in a copper sulfate solution, many impurities precipitate out, whereas other, more active metals, can't be plated out.  Now that makes perfect sense to me for extremely active metal cations like calcium, magnesium, and the like, but not for other, only slightly less active metals found with copper.

[pifi]

Yes, this was unwanted issue, sorry. I dont know how.. 

I readed the article(s) https://www.ausetute.com.au/electrowincu.html , so it is known for me how to clear solid metal to make pure metal.
But I asked how to clear a solution of different salts (different kations). 
i.e.
I have dirty electrolyte and I want to clear it by electrolysis. Is it possible ?
Practically I have 70-90% CuCl2 in solution, plus 30-10% NiCl2 in solution. How I can remove Copper or Nickel from solution to have one clear chloride in solution?

[Borek]

Part of the success is controlling the potential - if the difference between reduction potentials of cations is large enough (in practice 200 mV should be OK) you can electrolyze out one cation from the solution before the other starts to deposit.

Removing copper should be the easy part, it is nickel that will be more difficult. Still doable, but may require precise control of pH and addition of complexing agents.

[pifi]

Part of the success is controlling the potential - if the difference between reduction potentials of cations is large enough (in practice 200 mV should be OK) you can electrolyze out one cation from the solution before the other starts to deposit.

Removing copper should be the easy part, it is nickel that will be more difficult. Still doable, but may require precise control of pH and addition of complexing agents.

Yes, this is what I am looking for. For example, I have solution with unknown concentration salts vs. water. Very probably most of is CuCl2, then some percent of SnCl2 and NiCl2 as usual expected materials from dissolved electrical parts. (even maybe some palladium, lead, ... which are not filterable for me yet).
In past experiments where I dissolved PCB boards with just copper and gold, it was simple - I did gold flakes to be filtered out, and I got almost pure CuCl2. This CuCl2 I reacted with Fe , to get Cu crystals. From FeCl2 I am able to do FeCl3, nice liquid for all electrical hobbist doing DIY PCB at home.
But I came to more advanced tasks, where CuCl2 solution is dirty with other chloride metals/salts. How I can remove them ? - idea was use electrolysis and some inert electrodes, to get unwanted kations out of CuCl2 solution.

Where can I found electrochemical potencial tables for that ?  (Cu, Ni, Fe, Sn, Pb, ...) ?
Which electrode material I should use ? - same metal that I am removing, or some inert (inox, titan, ...) ?
Controlling potential is controlling of voltage used for electrolysis? or you mean use third electrode just for reference measuring ?

BTW, your idea to remove copper rather than nickel is also fine. If I get out Cu from CuCl2, then I can got weak solution of Sn,Ni,.. chlorides to be separated in other step. Right ?

[Borek]

Where can I found electrochemical potencial tables for that ?  (Cu, Ni, Fe, Sn, Pb, ...) ?

Google is your friend.

Note that what you will find will be table of standard redox potentials, your solution contains ions in different concentrations, so you need Nernst equation to calculate formal potentials. Even that is just a simplification, as presence of chlorides means cations are a bit complexed, so their formal potentials deviate even more.

One thing to remember and to check is pH control to avoid producing H₂ (that will compete with the metal reduction) and to avoid precipitation of hydroxides.

Which electrode material I should use ? - same metal that I am removing, or some inert (inox, titan, ...) ?

The same if often the simplest to use, but not necessarily the cheapest option.

Controlling potential is controlling of voltage used for electrolysis? or you mean use third electrode just for reference measuring ?

Depending on the solution, setup and additional details, both can be valid. With a correct selection of the solution composition just controlling the total voltage should be enough.

BTW, your idea to remove copper rather than nickel is also fine. If I get out Cu from CuCl2, then I can got weak solution of Sn,Ni,.. chlorides to be separated in other step. Right ?/quote]

There are many ways to separate cations, it is not like only one of them is correct. Yes, you can mix different ones, it is just a matter of choosing the cheapest and the cleanest one.

[pifi]

Great. It is much closer to help me.
Of course I used Google, but I am not expert from chemical area to understood every thing.

Ad.Theory,
I found more about redox potential and tables. If I calculate well, I will need similar voltage as calculated : CuCl2 = 0.337V - (-1.360V) = 1.697 V ... for copper crystalizing case.
Also as you mention, keep reaction and voltage regulated to not produce hydrogen bubbles. Right ?
Nernst equation I saw, but what to put here? e.g. molar concentration of CuCl2 or  NiCl2 is unknown for me.

For 25°C at normal Air pressure
E = 0.337V + 0.059 / 2 * log (Molar_conc) => unknown variable to complete

And what is purpose of Ph-metering?  Ph-paper indicators are ok, or must be electrical Ph-meter used ?

And back to mine issue,
- if I would like separate Copper first, I have to use copper electrodes and voltage similar to E = ... , or about 1.697V calculated above ?
- what happens if successfully I crystalize copper, the concentration of H2O + NiCl2 decreases ? ... respectively less ions/chlorides in same volume of water?
- then If I would like separate Nickel from copper clear solution, then I have to use Nickel electrodes, and another voltage ?
- at the end, the water with few ions and rest of heavy metals sustain in solution ?




 ...

[Enthalpy]

https://en.wikipedia.org/wiki/Standard_electrode_potential

Impurities precipitate out: I suppose that
- When one electrode gets thinned by the current, all its elements are drawn into the liquid
- Depending on the composition of the electrolyte, some elements can make insoluble compounds that precipitate.

Deposition of the more noble metals first sounds reasonable. Deposition from a solution only is what a charging accumulator does. It needs a moderate voltage that results in a small current density and a slow process - more so if the metals to separate have a similar potential. A concentrated electrolyte helps at least this, and wide close electrodes too.

A metal can be deposited on a different one by electrolytic methods. This is common in mechanical construction, often as a protection against corrosion. The voltage to apply depends on the choice of both electrodes: you make a battery, and the external circuit works with or against the cell voltage. The possible choices for both electrodes depends on the solution too, or you get side reactions, like copper depositing spontaneously on iron.

While gold should be worth it, I suggest to double-check the cost of electricity compared with the value of the regained metals. For mass-production of copper and aluminium, cheap electricity at huge industrial size is a big fraction of the metal price, so if you pay the kWh as an individual, Sn, Cu, Ni... are probably not worth it. This can be done early, even before deciding details about the compositions of electrodes and solution, by picking some arbitrary voltage.

[pifi]

*MOD Edit -- remove pointless quote*

Very thanks! I tried to translate/understood everything, but I am not sure If I got it all.
My case is that I can have pure metal electrodes, but I have unclear electrolyte solution of few salts. I am trying use electrolysis process to clear dirty solution and remove salts, metals one per one. Two usual cases I have - separate Pb and Sn chlorides, and separate Cu and Ni chlorides from solutions. (maybe Palladium and Silver is content also)

If I understand , I have to use low current density, big electrodes and nearly saturated solution of electrolyte. Electrodes I can choose, but with respecting i.e. replacement (Fe by Cu, ...) and when considering power source voltage, that should be a little bigger than cell voltage, right ?  (cell voltage I will get from Standart Electrode Potential equations, right ?)

BTW. previously I used Fe to replace metals from Cu,Ni,Sn chlorides solution. It works well, but I got impure metal dust with Cu+Ni+Sn

I am processing very small quantities "in hobby cases", e.g. below 1kg. So I don't consider kWh energy costs.

Thanks!