Plating copper from waste solutions

I am interested in the method described below to produce a plated deposit of copper from waste solutions.
I think it would be very useful to have a large piece of copper instead of a copper powder to be able to scrap it directly or use it for cementing silver or other PMs.

The process seems pretty straight forward, but I I haven't turned up any other mention of this process here or through Google.
Does anyone have any pointers to articles or additional keywords I could be using to find out more about this method of copper recovery from waste solutions?

Thank you,
Bill

Taken from:
http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=45&t=8569#p105318

pesco said:

If you want to cement Cu with iron scraps the best way is to take Cu sheet, using copper wire connect it with iron scrap and submerge the connected bits in the liquid you want to drop copper from. Make sure the wire link between both pieces of metal is above the liquid level. If surface area of copper sheet is bigger (the bigger difference the better) than surface area of iron scrap then most of the Cu will cement on top of the copper sheet as a layer of solid metal. By playing around with surface areas and temperature (pH doesn't play significant role in my experience as long as the solution is acidic) you could get all Cu out as a plated deposit and you could eliminate the need of filtration.


What you are doing is creating a battery. Because of standard electrode potentials copper is more likely to deposit on copper then iron. When copper atom deposits the Cu²⁺ ion needs 2 electrons. At the same time Fe atoms want to get rid of electrons in order to forms positive ions (Fe²⁺ and/or Fe³⁺). The wire link between copper sheet and iron scrap provides easy way for electrons to travel from one end to the other, thus speeding up significantly the whole process.
At the same time, because Cu deposits on different electrode than Fe ions are taken from the Cu deposits do not block electrolyte from beeing in touch with Fe scraps what speeds up the process even further.

The smaller distance between copper sheet and iron scrap the better - smaller travelling distance for electrons.
The thicker the wire link between cooper sheet and iron scraps the better - thicker wire means less resistance.
The best wire link is copper one - lowest resistance.

Have fun :mrgreen:

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Sounds like an interesting experiment. I would set it up in a 5 gallon bucket of the copper containing waste material. Put in a sheet of copper metal that is almost the diameter of the inside of the pail and tall enough to stick out of the solution a few inches. Then put in a sheet of steel half the diameter of the pail and as tall as the copper sheet so it too sticks out of the bucket. Somehow brace them so they do not touch. Then make a short set of jumper cables with heavy copper wire and clamp one on the copper above the solution and one on the steel above the solution. I would add an airstone to move the solution about and speed things up.

As pesco said in his post, try various sizes of steel sheet to see what size ratio works best.

Interesting concept, please get back to us with some results and pictures.

i like this idea copper precipitant is such a pain to deal with this seems like a much better way and a simple step to add to the waste stream! i will give it a go and post resulsts.

Revisiting a somewhat old topic...

I like the idea of plating out the copper as described above, but if I understand the reactivity series correct, this would also plate out any Lead, Nickel or Tin in the solution as well, right? So, toxicity aside, the plated copper would be purer if plated out with a Lead anode. Of course, regarding the whole of the reactivity series, Antimony or Bismut would be even better, but those are not too common in the waste stream as far as I understand.

The reason I want to revisit this is because I have just about finished a small batch of pins with solder on them. The AP I used will then likely contain both Lead and Tin, and likely some Nickel. I have only done a small batch, so the entire volume of my dirty AP-solution is around 1500ml, which would make for a good size to do some small experiments.

I will take two small portions and set up the reaction using Lead and Iron. If I weigh the pieces used for each setup before and after the reaction, using the same volume of AP-solution, that should give me the alternative to calculate the amount of materials deposited on the Copper cathode. From the same amount of Copper-containing solution, the Iron anode should then deposit a greater mass due to Pb/Sn/Ni mixed in with the Copper.

I will be back in a day or two with some pictures, and we'll see what the final verdict is.

I think that a lead anode would have a couple of issues. To begin with adding more lead to a toxic solution seems contra productive when the alternative with iron isn't toxic. Iron is also quite cheap compared to lead. The second issue is that lead chloride have a limited solubility so the anode would passivate quite fast.

My guess is that a lead anode won't work at all but the iron anode could do quite good. The quality of the deposit can be quite bad and create a copper moss that are easily shed... or it could create a good deposit, all depending on the other content in the liquid, acidity, temperature and so on.

I'm looking forward to see the results though and wish you luck.

PS. to remove lead, dissolve some iron in sulfuric acid and then use the iron sulfate to precipitate the lead from the solution before recovering the copper. Iron sulfate shouldn't add any problem for the copper recovery.

Göran

Posted as questions, since I'm not an expert by any stretch:

Isn't the electromotive series of metals what should be considered in electrolysis, not the reactive series?

Would electrolyte get fouled fairly quickly if it's not mostly copper ions as the metal component (in reference to the lead/nickel/tin content)?

upcyclist said:

Posted as questions, since I'm not an expert by any stretch:

Isn't the electromotive series of metals what should be considered in electrolysis, not the reactive series?

Would electrolyte get fouled fairly quickly if it's not mostly copper ions as the metal component (in reference to the lead/nickel/tin content)?

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That might be, I'm not sure either, but if I interpret the electromotive series correctly, the net result would be the same regarding Lead and Iron versus Copper, with Iron as the anode producing a slightly higher voltage output. As for the condition of the electrolyte, the idea would be to replace the Cu2+-ions in the electrolyte with Pb/Fe-ions respectively, and while the Iron anode would account for a higher voltage to drive the reaction through to completion quicker, the Lead anode would yield a purer result, I think...

But that is why we experiment, to test theories and gather empirical data, hoping to get some kind of confirmation or proof. I will be doing this in a quite small scale to limit the amount of Lead-containing waste liquid, but it needs to be of some volume to produce significant differences in weight gained from the plated metal on the cathode. I will set it up tomorrow, likely in small beakers with 200ml in each.

Reading through the process now, I realize I might omit the entire issue with Lead by adding sulphate. Of course, Gøran beat me to it... :lol:

I will expand on my original plan and add a third beaker with Iron as the anode material, but I will first add an excessive amount of a soluble sulphate salt.

I don't see how this can be so. If the iron is giving up it's electrons, why would they flow over to the copper side and cause the copper to plate out on the copper? It would seem that idea violates the fact that electricity or electrons travel the path of least resistance. If the copper ion is next to iron plate, surely the battery is right at the junction between those two atoms and the electrons would get transferred to the copper ions that are "in contact" with the iron. Just my thoughts on this.

geedigity said:

I don't see how this can be so. If the iron is giving up it's electrons, why would they flow over to the copper side and cause the copper to plate out on the copper? It would seem that idea violates the fact that electricity or electrons travel the path of least resistance. If the copper ion is next to iron plate, surely the battery is right at the junction between those two atoms and the electrons would get transferred to the copper ions that are "in contact" with the iron. Just my thoughts on this.

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That might well be the result, this is not 'my' kind of chemistry, hence the experiment. In theory, I'm setting up a simple galvanic cell, or battery, if you will. Based on the different metals' willingness to give up electrons, as it were. Iron will more readily give up electrons than Cu (and Pb/Sn /Ni), in the process donating these electrons to the metals that cling harder to them. The driving force is the difference in this willingness, generating a current. The electrons donated by the Fe-anode do not go into solution, in theory, instead opting for the path of least resistance, as you pointed out, provided I short the circuit with a thick enough wire with a low resistance. I will bring my trusty volt-meter to measure the current as well.

This would make a positive and a negative electrode, thus attracting the cations and anions to them. Hopefully that attraction will be enough to make the Cu stick to the cathode by metal bonds, but if the current is too low (due to the low electric potential between the cathode and anode) I could end up with a really poor electroplated spongy mass, as Gøran pointed out.

But we'll see, I guess. For me, this is the fun part, the actual chemistry after several hours of mechanical preparation of the materials.

Mind you, my above post could simply be a great mess of confused thoughts as I just woke up and am still sitting in my bed, gathering the will to go make coffee and wake the girls up for school. Will be back later today with preliminary thoughts on the experiment.

Well, the short version is; it didn't work.

The slightly longer version is that it did work, but not as intended. I set up my reaction cell:


I made three, as originally planned, but the general setup was the same, so to save space I'll only post the one. I made 2 with an Iron anode and one with Lead. I measured out 150ml of my dirty AP-solution after it had been bubbling over night with a bunch of copper to cement out any valuables. To one of the Iron-anode-cells I also added Ammonium Sulphate to precipitate out the Lead from solution, as described in a previous post. Then in went the 150ml of AP into each of the cells. I also tested the sulphate on a small batch beforehand, and though I have no tests to prove it, there was visible white, insoluble precipitates formed upon addition that I assume are Lead Sulphate. I will, however, go through my old chemistry book to look for other sulphates that might form and drop out as well.

Having looked a bit closer at the reduction potential of the metals, I calculated that an Fe/Cu-cell would generate around 0,6V of potential, while the Pb/Cu would be somewhere slightly below 0,3V. The measurements were inconclusive, but lower for Pb/Cu than the two Fe/Cu ones, though all three were way below estimated, at 0,08V, 0,13V and 0,14V respectively.

So it looked like this would take a while, and as I prepared to push the cells to the back of the hood and do something else, I noticed a curious thing; Both electrodes were visibly plated with Copper:


Naturally, I stopped the experiment, removed the electrodes and rinsed them well before gathering up the electrolyte (the dirty AP solution, now with Ammonium Sulphate added), and paused to review the results.

It appears that geedigity had a very valid point: the Copper does indeed plate out on the Iron as well, though judging from the look of the electrodes, Copper was deposited on both sides.

For now, my working theory is that the electric potential of the reaction is too small to overcome the proclivity of Iron to 'trade' electrons with Copper completely, thus creating a situation where there is a reduction of Copper taking place at both electrodes.

What I don't get, is why the Copper metal formed at the Iron electrode is plated onto it, rather than just formed as a free-flowing precipitate. It might be that the possibility of making a metal bond with Iron exhibits some kind of force as well, but that is outside my realm of knowledge.

Another curious thing also happened, and this one I throw out to you guys: The Copper cathode paired with the Lead anode did not get a covering of bright Copper as the others, but instead a dull, whiteish Copper-colour:


Anyone care to take a guess at what happened to the Cu-cathode here?

On a side note, the Ammonium Sulphate appears to do a fairly good job of removing the Lead from the waste-AP, so I gathered up the various small amounts of AP from the cells and mixed it with an excess of (NH4)2SO4 to see if I can get the Lead out before dropping the Copper. Obviously, this will add a step to the waste treatment, but the idea of ridding the solution of Lead seems like a good one, and I will gladly spend the time to precipitate and filter out the Lead Sulphate if that gives me a less dangerous Cu-powder to use in my Stock Pot later on.

To add some information, I was wrong. I set out to see for myself what would happen. I connected a 1/2 inch diameter iron rod that was about 7 inches in length to a piece of copper buss bar that was about 2.5 inches x 0.5 inches x 6 inches and suspended the joined copper and iron in my 5-gallon bucket I use as my stock pot.

After about 15 minutes, I saw that the iron had the typical copper build-up (moss) and could not really tell if the copper buss bar had any deposition occurring on it. I left it over night and the picture below shows what I found. I scraped a bit of the copper deposit from the bus bar to depict the depth of the deposit (approximately 1/16 to 1/8 inch)


So I am correcting myself.

It is worthwhile to note that the deposits on the copper bus bar were not like the typical moss that is produced when submerging iron in the stock pot. The deposits were much more compact and had larger crystals.