[eprigge]

I'm looking for simple and cost effective methods to separate/purify nickel from copper held in solution or from an alloy melt or powder.

So far I can only think of a few methods and they aren't very practical:
 - carbon monoxide volatilizing the nickel to nickel carbonyl. (probably very effective but far too dangerous)
 - electroplating out the copper (slow, especially with high concentrations of nickel in solution)
 - oxidizing out the nickel from a melt (perhaps with an excess addition of a copper oxide)

I figure that there has to be some simple method of selective reduction that will precipitate the copper out of a solution leaving all of the nickel behind.  Something like the Fehling's reaction perhaps.  Or some 'electroless' type plate out of the copper.

Any ideas?

[nezza]

I don't know if this will work. I have used the method to separate copper from silver.

Dissolve in Nitric acid and evaporate to dryness
Carefully heat the nitrate mix in a fume hood
Copper nitrate decomposes at a very low temperature so you may be able to decompose the copper nitrate to copper oxide while the nickel nitrate is largely unaffected.

[eprigge]

Interesting idea nezza, thanks.  Nickel nitrate (hydrate) boils at only 137C so perhaps it could be distilled away from the copper nitrate.  Probably wouldn't work very well though since it's also converting to the anhydrous form at that temperature. 

Even if it worked it wouldn't be so practical due to the expense of the nitric acid.  I want to find ways that use cheap reagents (hydrochloric acid, sulfuric acid, etc.).

[408]

Actually the CO method is not too bad if done right.  
Find out if the reaction is endo or exo between CO and Ni

Then seal the powdered alloy in one side of a glass tube, pressurize with CO, and heat the tube with one side hotter than the other (decided based on whether rxn is endo or exo) and pure Ni will crystallize on the opposing side.  

[zeshkani]

run the nickel with excess CO  and once you have NiCO4 , heat this up 200 this will make you nickel

look up the mond process

[ardbeg]

carefully dissolve the metal mixture in acidic media and get final pH = 2.  extract with an organic solution of a phenolic oxime reagent.  wash organic phase with clean aqueous sulfuric acid (pH = 0) and you should have aqueous copper sulfate.  Electroplate.

[eprigge]

408, the sealed system idea sounds interesting.  Were it not for the outstanding toxicity of nickel carbonyl, that would be the obvious process to go with.  According to a little googling, nickel carbonyl has an LC50 of 3ppm for 1/2 hour exposure (about 1/2 mg)...  that makes cyanide look benign.  Anyway, that's a good idea, I'm sure something sealed could be designed that uses convection/density differences to pump CO/Ni(CO)4 through the system from the cool to the hot ends.

ardbeg, I hadn't run into that idea yet, thanks.  Apparently those phenolic oximes are widely used in mining to selectively separate copper, nickel, cobalt, etc.  Lots of good patent data to look at.

[ajkoer]

 I noticed there is a large difference in the solubility of NiI2 (124g at zero degrees C) in water versus CuI (insoluble).

 If you devised a process that recycled the iodine, it might be efficient and cost effective.

[ajkoer]

To create the iodide salts, Iodine reacts directly and vigorously with Nickel. CuI can be prepared by passing iodine vapor over heated finely divided Cu. Alternately, and possibly best, would be by dissolving Ni (CuO) in concentrated HI to form NiI2 (CuI).

 To recover the metals, react the CuI (NiI2) with Fe.

 Reacting Ferric Iodide with H2SO4 or HCl should recovers the HI. Also, by passing a small amount of Cl2 over heated Ferric Iodide could recover the Iodine (however, watch out for Chloro-Iodine compounds).

[James Lum]

The easiest way to do so that i can think of is to dissolve your Cupronickel alloy in Sulfuric Acid and Hydrogen Peroxide , when the reaction is complete , and make sure there is no more Sulfuric acid , dry the solution off , best is to let it boil it and let it out to dry off Remember , do not just crystalize the salts right out of the solution , the different metal sulfates have high solubility and Nickel is way more soluble then copper sulfate. so just leave it out and let it dry out completely. Do not heat it until it turns in to the anhydrous form or else this will not work. with the coper sulfate pentahydrate and nickel hexahydrate in the form of crystals , soak it in Ethanol then filter off the residual crystals. then let the filtrate mixture evaporate off and you can retrieve your nickel sulfate hexahydrate in a pure form. Just to be sure , do this a few times until there is no more percipitating out of the Ethanol filtrate that has been left to evaporate off. There ya go ! Simple and pure !

[AndersHoveland]

If you heat a mixed solution of silver and copper salt with persulfate, the nickel should precipitate out as NiO2 (referred to as "nick peroxide", although actually nickel in hte +4 oxidation state)

[Ksharindam]

Yes i have a methode to separate copper from nickel using HCl or H2SO4.YOU have to boil the alloy with hydrochloric or sulfuric acid.so nickel will form nickel sulfate and H2.and copper will remain intact.filtering the solution copper will be separated.the make the solution concentrated and separate nickel by electrolysis

[Borek]

Concentrated sulfuric acid dissolves copper, doesn't it.

[Arkcon]

Concentrated sulfuric acid dissolves copper, doesn't it.

Not as easy as you'd think.  To dissolve pure copper in sulfuric acid, you need to constantly bubble air through.  I don't know if nickel behaves the same way.  In that case the boiling may mix some air in, and help copper dissolve.

[Ksharindam]

Ni+2HCl=NiCl₂+H₂
Boiling with HCl will dissolve nickel but will not dissolve copper which will remain unchanged.filtering and reboiling the solution you will get concentrated nickel chloride solution.extract nickel from this solution by electrolysis using two carbon electrode.