# What are possible anode materials for copper(II) sulfate electrolysis?

I'm a student doing a research paper about copper sulfate electrolysis with an experiment by varying anode material, and aside from Pb and graphite (and pure Ti which I think wouldn't work without further alloying) I haven't been able to find or source feasible anode materials as most studies I've found called for Ti-alloys and Pt. I'm also trying to see if Fe, Al, and Zn could be used but I haven't found any literature which even mentions the possibility of using them.

Edit: My research paper was originally focusing on electrowinning copper, but because of circumstances being as they are I've had to simplify my methodology to using copper sulfate with added sulphuric acid and iron salts to at least somewhat replicate electrowinning electrolyte conditions.

• If it's a research paper, I'd try to test as many metals and alloys (e.g. bronze, brass) as possible (also think of various stainless steels, maybe some screws or alike will do, just grab what you can get) and check what will happen when the metals are used as anode or cathode. For testing cathode materials, it might a good idea to use a copper anode and v/v. Also, are you supposed to use copper sulphate alone or should you add some sulphuric acid to increase conductivity (which might change the behoviour of some metals)? – imalipusram Apr 22 at 15:53
• Why don't you test Copper ? With a copper anode, you will produce exactly the sane amount of Copper ions in the anode the you reduce at the cathode. So the composition of the solution will not change with the time. Anyway don't try with Fe, Zn, Al, or any other reactive metals, as they will react with copper ions even without electrolysis : $$\ce{Fe + Cu^{2+} -> Cu + Fe^{2+}}$$ – Maurice Apr 22 at 19:50
• My research paper was originally focusing on electrowinning copper, but because of circumstances being as they are I've had to simplify my methodology to using copper sulfate with added sulphuric acid and iron salts to at least somewhat replicate electrowinning electrolyte conditions. So using copper anodes would be somewhat redundant, but thank you anyways I should have specified. – Sean Jordan Apr 23 at 12:48

Iron, Aluminum and Zinc are all significantly more reactive than Copper, so they will react with the Copper Sulfate and displace the Copper. I'm assuming that's not what you're trying to do, so you'll likely have to use an inert metal (Platinum, Gold, Silver) that conducts electricity well as your anode.

Edit: When I say that Iron, Aluminium and Zinc are more reactive, what I mean is they have a greater electropositivity compared to Copper and are, therefore, more likely to donate/lose electrons to form positive ions.

• When you mean more reactive, is it mainly because their standard potential is higher than Copper's? – Sean Jordan Apr 23 at 12:44

The first step should be to ask a question so that you can get an answer which gives you data that you can analyze and discuss. Research generally tries to ask a question that results in some improvement for the world. How to better electrowin copper would be a good question. It seems that you are not just looking to move copper from one electrode to the other, but to understand what might be going on within the solution, because, after all, impure copper in one place is not that different from pure copper in another place.

What is the question that changing anode materials will answer? Different anode materials may dissolve (or not) and change the composition of the solution, which could be desirable, or it might be considered a contamination. Different anode materials will give different voltage vs current curves, because active metals will assist the electrolysis.

In a commercial environment, purifying copper should be routine until the solution becomes so loaded with active metal contaminants that voltage adjustments have to be made to continue plating purest copper, and now a decision has to be made about disposing of the solution. More noble contaminants, like silver and gold would precipitate.

So what could you do with a solution of copper sulfate and ferrous sulfate? Zinc has been mentioned as a frequent impurity, but in large operations, nickel is the soluble impurity of considerable value https://metalrecyclingmachines.com/metal-recycling/metal-recovery-systems/copper-electrolytic-refining-plant.html Lower pH keeps some metal hydroxides in solution rather than precipitating, but will increase the electricity needed to transport a given amount of copper. Nickel sulfate may not be available for you, so I suppose ferrous sulfate could be used.

Perhaps you could pick one anode material and vary the solution to mimic the end of life solution loaded with impurities (in your case, ferrous sulfate). In this case, an iron anode would seem best. Then with variable ratios of copper to iron (and perhaps at a couple of pHs, since this could be changed to assist the process), what voltages, or probably better, what current densities (amps/cm^2) are optimal for squeezing the last bit of copper out of the solution? So the anode could remain the same composition, but vary in area. (You will also have to try just dumping in a wad of steel wool - skip the electrolysis. This is an out-of-the-box shot to just see what will happen. No guarantees.) I suspect that too low a current takes too long but will give pure copper output (as seen on a stainless wire cathode), while a high current density will get the copper out of the solution faster, but it might be contaminated (how? air, iron, solution - I don't know).

Good luck. Be safe.