Sciencemadness Discussion Board

Electrolysis of acid Cu2+ solution

me2 - 12-10-2012 at 05:11

Hi all,

I want to precipitate Cu out of an acid Cu2+ solution. But have some questions.

First of all let me give you a visual picture of my set up



Pot B contains a Cu2+ solution in HCl. I want it to precipitate on the cathode

In pot A I would use a Al plate as electrode (prossible with small contaminations like Zn or Pb).

If I'm correct, Al3+ ions wil emigrate to the Cu2+ solution, but will not precipitate because the reduction of Cu2+ will come first. Even after that no Al3+ (nor Zn2+ or Pb2+) will prepicipate because of the presence of H+ (which will reduce first to H2)

Am I correct this far ? Any remarks yet ?

What I don't know is how much voltage I can apply to the system. I thought current will drive the speed of the reactions. But what about voltage. Is there a possibility that H+ will reduce along Cu2+ if the voltage is to high ?

edit - edit - edit .... typos - typos -typos



[Edited on 12-10-2012 by me2]

[Edited on 12-10-2012 by me2]

[Edited on 12-10-2012 by me2]

[Edited on 12-10-2012 by me2]

[Edited on 12-10-2012 by me2]

weiming1998 - 12-10-2012 at 05:31

Quote: Originally posted by me2  
Hi all,

I want to precipitate Cu out of an acid Cu2+ solution. But have some questions.

First of all let me give you a visual picture of my set up



Pot B contains a Cu2+ solution in HCl. I want it to precipitate on the cathode

In pot A I would use a Al plate as electrode (prossible with small contaminations like Zn or Pb).

If I'm correct, Al3+ ions wil emigrate to the Cu2+ solution, but will not precipitate because the reduction of Cu2+ will come first. Even after that no Al3+ (nor Zn2+ or Pb2+) will prepicipate because of the presence of H+ (which will reduce first to H2)

Am I correct this far ? Any remarks yet ?

What I don't know is how much voltage I can apply to the system. I thought current will drive the speed of the reactions. But what about voltage. Is there a possibility that H+ will reduce along Cu2+ if the voltage is to high ?

edit - edit - edit .... typos - typos -typos



[Edited on 12-10-2012 by me2]

[Edited on 12-10-2012 by me2]

[Edited on 12-10-2012 by me2]

[Edited on 12-10-2012 by me2]

[Edited on 12-10-2012 by me2]


Why even make such a complex setup? Cu2+ solution (you don't even have to dissolve it in HCl(aq)) can be electrolysed directly to produce copper at the cathode. While in your setup, some Al,Zn and Pb will indeed go into solution as the ions, I see no point in this. Simply using an inert graphite anode will work, as the Cl- ions are oxidized to Cl2, which bubbles out. And why keep the two solutions separate?

An efficient way of producing copper powder is using a copper anode and an inert cathode (copper, graphite, platinum, any thing that won't be dissolved into solution by the Cu2+ ions). Simply hook the electrodes up to a power source and place them in a beaker of CuCl2(aq) or Cu2+ acidified by HCl(aq) . The copper at the anode will be oxidized by the Cl2, forming CuCl2, which goes into solution and plates out as copper at the cathode. The anode will slowly dissolve away, while copper powder gathers at the cathode.

If you simply want to recover the copper from the Cu2+ solution as metal, then do exactly as above, except replace the copper anode with an inert material such as graphite.

A non-electrochemical way of doing this is by adding Al foil to the Cu2+ solution. The Cu2+ ions react with Al in a single displacement reaction to form Cu metal and Al3+. Simple.
[Edited on 12-10-2012 by weiming1998]

[Edited on 12-10-2012 by weiming1998]

me2 - 12-10-2012 at 06:09

Hi Weiming1998, tnx for your reply.
Quote:
Why even make such a complex setup?


Well partly because I don't know better :P . But there are a few if's.

1) The Cu2+/HCl solution is a fact, nothing to change about that. (well almost nothing. HCl could probably be changed by H2SO4)
2) I don't like the fact of producing Cl2 gas, so I was looking for an alternative.
Quote:

And why keep the two solutions separate?


Because an Al elektrode in acid would work :cool: Keeping the solutions seperated was a way around this problem.
Quote:

If you simply want to recover the copper from the Cu2+ solution as metal, then do exactly as above, except replace the copper anode with an inert material such as graphite.


In fact that's what I want to do, but without the formation of Chlorine gas.

Would be the use of H2SO4 in stead of HCl a solution? SO42- could be oxidated to S2O82- . But I'm not familiar with the persulfate-ion . I guess it's stable and wouldn't do anything strange.



[Edited on 12-10-2012 by me2]