Sciencemadness Discussion Board

seperation of cobalt and copper

KaliyaK - 15-1-2020 at 07:30

Hi everyone, i recentry tryed to isolate cobalt metal from lithium ion baterys but had a lot of copper contamination... I dissolved everything i had (from the aluminium reducion) in hcl so now i have a solution of cobalt and copper chlorides. If i reduce them with aluminium i will end up with both metals as a powder. i tryed to dissolve the copper in hcl as cobalt reacts very slowly at room temp but some does go into solution and not all copper is removed... Any sugestins? I'm not to familiar with cobalt chemistry...

Will acetic acid + h202 attack cobalt?
Different reducing agent?

Thanks! :)

WGTR - 15-1-2020 at 08:38

Cobalt and nickel tend to react similarly in chemical reactions, and I have found that nickel and copper are difficult/messy to separate from one another. There is an extensive thread on here on that topic that may be of use:

http://www.sciencemadness.org/talk/viewthread.php?tid=16811&...

Here is a shorter thread on isolating cobalt from copper:

http://www.sciencemadness.org/talk/viewthread.php?tid=85051

If you have a concentrated solution you may be able to slowly remove the copper by electrolysis. However, you'll likely need very low current density to keep from plating out the cobalt with it, and some cobalt will start plating out as the solution depletes in copper.

Armus_ - 25-1-2020 at 11:16

just neutralize the chloride solutions to around a ph of 7 and then titrate the copper out using potassium iodide. the Cu2+ should be turned into CuI which precipitates out. of solution. then when that is done and you filtered it, it will be a dark reddish-brown color. that's because of elemental iodine in solution. you can either boil it out until there is no iodine color in solution or add sodium thiosulfate until the iodine color is gone. then you will have the color of cobalt chloride left. then just extract the cobalt metal as usual.

unionised - 25-1-2020 at 12:32

YOu can also try adding sulphite to reduce the copper and precipitate it as the chloride.
Probably cheaper than iodide.

mayko - 25-1-2020 at 14:17

What about thiocyanate? My understanding is that the cobalt complex is soluble in organic solvents; this extraction of Co from a Ni/Co relies on this difference in solubility:


Attachment: NiCo_separation.pdf (703kB)
This file has been downloaded 380 times

In the case of copper contamination, that might not even be necessary - Cu(SCN)2 precipitates as a quasi-stable solid:

Attachment: Tudela - 1993 - The reaction of copper(II) with thiocyanate ions 2.pdf (811kB)
This file has been downloaded 371 times

WGTR - 25-1-2020 at 16:17

Quote: Originally posted by Armus_  
just neutralize the chloride solutions to around a ph of 7 and then titrate the copper out using potassium iodide. the Cu2+ should be turned into CuI which precipitates out. of solution. then when that is done and you filtered it, it will be a dark reddish-brown color. that's because of elemental iodine in solution. you can either boil it out until there is no iodine color in solution or...


This does work, but the iodide salt is expensive. I have a small leftover bottle of CuCl that resulted from this experiment.
Quote: Originally posted by unionised  
You can also try adding sulphite to reduce the copper and precipitate it as the chloride.
Probably cheaper than iodide.


How about simply adding powdered copper metal? I have a gallon solution of copper(II) chloride in HCl solution for etching copper circuit boards. The resulting CuCl is soluble so long as the pH is kept low enough with excess HCl, otherwise is begins to precipitate. Excess HCl would allow the reduction to take place more completely, then perhaps the pH could be adjusted to precipitate the chloride salt.

In any case, reduction to CuCl should take place away from air. I normally used a sealed boston round. Otherwise oxygen in the air re-oxidizes it.

unionised - 26-1-2020 at 01:54

The difficulty is that, in the presence of excess HCl, the CuCl is soluble.
You can ppt it by adding lots of water.
But that's difficult without adding lots of air.
and, of course, you then need to recover the Co from a more dilute solution.

Fery - 26-1-2020 at 10:03

Hi KaliyaK, I did similar cation separations more than 25 years ago and luckily I found the brochure, so just rewriting the Fresenius method of separation of cations:
Adding HCl precipitated group 1 (Hg2Cl2, PbCl2, AgCl) which was then filtered out - this is not your case. It is important just to know that the filtrate stayed acidic then.
Then adding aqueous H2S precipitated group 2 as HgS, Bi2S3, CuS, CdS, As2S3, As2S5, Sb2S3, Sb2S5, SnS, SnS2, which was filtered out.
To the filtrate was then added aqueous (NH4)2S which precipitated group 3 as NiS, CoS, Fe2S3, MnS, Al(OH)3, ZnS, Cr(OH)3 which was filtered out.
Then to the filtrate NH4Cl, NH4OH, (NH4)2CO3 was added which precipitated group 4 which was filtered out and group 5 stayed in solution - this is not your case.
Group 2 after washing the precipitate on filter paper with (NH4)2Sx was also divided into subgroups 2a, 2b:
2a precipitate HgS, Bi2S3, CuS, CdS
2b filtrate (AsS4)3-, (SbS4)3-, (SnS3)2-

So you can precipitate both Cu, Co as sulfides, Cu precipitates in acidic environment where Co doesn't. This method is used in analytical chemistry and I doubt whether it is economical at larger scale... for final exam we received testing tubes with a mixture of various unknown cations where each cation content was at mg scale. Also be careful of H2S toxicity!

KaliyaK - 30-1-2020 at 14:12

Hello everyone thanks for all the help!

So current options are:

1. Ph7 and remove copper with KI sol.;
2. Direct percepitation with thiocianate;
3. HCl excess, remove copper with H2S and cobalt with (NH4)2S;

I do have a small quantity os KI so i'm going to try that methode im a small test tube to see how much is nedded to percipitate all the copper. The thiocianate seams easy as well but i dont have it at the moment... The H2S methode looks to be great and simple and i do have some K2S but it will be my last resort due to the danger of the gas... One thing that got to me the other day was that if it's possible to seperate the cobalt powder from the copper powder using a magnet? Cobalt is magnetic where as copper is not so it might work no? I will try it once i have the oportunity and then i will report!

Thnaks everyone for the help!

Fery - 31-1-2020 at 13:49

Co (s) + CuCl2 (aq) -> CoCl2 (aq) + Cu (s)
Addition of Co metal into solution of CuCl2 + CoCl2 produces Cu metal which could be filtered out and pure CoCl2 solution remains.
Then reducing pure CoCl2 by Al wires/plates etc produces Co metal (part of it will be used in the next round) and unreacted Al removed mechanically - you have to use something from Al which could be easily mechanically separated.
For the first run you can use impure mixture of Co+Cu which you already obtained.
It is necessary to know the amount of Cu2+ contaminant not to waste too much Co for reducing, anyway some excess of Co is necessary. Your main goal is to obtain pure Co. The first step is to obtain pure Co2+.

rockyit98 - 31-1-2020 at 21:08

Quote: Originally posted by Armus_  
just neutralize the chloride solutions to around a ph of 7 and then titrate the copper out using potassium iodide. the Cu2+ should be turned into CuI which precipitates out. of solution. then when that is done and you filtered it, it will be a dark reddish-brown color. that's because of elemental iodine in solution. you can either boil it out until there is no iodine color in solution or add sodium thiosulfate until the iodine color is gone. then you will have the color of cobalt chloride left. then just extract the cobalt metal as usual.

haha! if you got thiosufate just add it to the neutral salt mix and heat it.as we learned in school cobalt sulfide is only made in a basic mixture. also can use H2S to precipitate only CuS in acidic solution. because H2S is toxic

it go like this. Cu+2 +Na2S2O3---------> +2Na+ +CuS2O3
H2O +CuS2O3 ----(heat)--->CuS + H2SO4

nezza - 4-2-2020 at 07:28

One way that might work is to convert both to nitrates and heat the solid carefully. Copper nitrate has a very low decomposition temperature and should decompose to the oxide before the cobalt nitrate does. I have used this to remove copper from sterling silver and leave pure silver nitrate.

Armus_ - 4-2-2020 at 08:18

Quote: Originally posted by rockyit98  

it go like this. Cu+2 +Na2S2O3---------> +2Na+ +CuS2O3
H2O +CuS2O3 ----(heat)--->CuS + H2SO4


huh i didnt know that, so i guess the best method for getting the iodine out is to filter the CuI and then boil the solution so the iodine would get out of solution

sbreheny - 7-2-2020 at 13:33

If you can get the cobalt in the metallic form (even if mixed with other metals or compounds), you can use a strong magnet to pull it away from the mixture.

rockyit98 - 7-2-2020 at 17:28

one time i separated nickle from copper by adding Mu-metal from HDD a to the solution so that copper is displaced by Ni and iron in the Mu Metal which is 80% Ni. added ammonium carbonate and heat it so all the Ni 2+ made ammonium complex while Fe doesn't filter the solution and i got my Ni out. https://en.wikipedia.org/wiki/Reactivity_series according to this if you add Sn to the mix only copper will deposit then you can dissolve Co2+ in ammonium carbonate so Sn2+ stays in the bottom.

KaliyaK - 27-2-2020 at 07:58

Hi everyone! First and foremost, want to thank all the comments and suggestions to my question and everything that i have learned!
With that said, i present my final result of cobalt beads! Ended up redoing the experiment tryed to purify the copper-cobalt solution but somehow there as too little product... Opened two more batterys that i had left (around 3000mAh each) and dissolved the black powder in hcl but did not left the copper eletrode in solution. With the help of a spay bottle and repeted washes in the hcl solution was able to remove all black compont without reacting with the copper leaving a pure cobalt/aluminium solution. From there the cobalt was reduced and melted in a arc furnace. The result was 12g of pure cobalt metal.

WhatsApp Image 2020-02-27 at 15.46.15.jpeg - 169kB

sbreheny - 27-2-2020 at 09:37

Very nice!