Bedlasky - 15-4-2021 at 09:25
Hi.
I tried to make some copper powder by heating copper sulfate solution with iron nails. Copper sulfate solution was made from copper hydroxide and
sulfuric acid. I did this few years ago in high school lab and it work really well. But when I try it know, it don't work. On surface of iron is some
copper, it look like passivated. I tried to add some hydrochloric acid as complexing agent, which might help with reaction. But even after that and
hours of heating nothing happened.
Any ideas?
unionised - 15-4-2021 at 09:46
Once the nails are covered in copper the solution can no longer get to the iron to react.
Try using steel wool and stirring or shaking it from time to time.
Johnny Cappone - 15-4-2021 at 10:38
As noted, the Cu layer formed on iron will prevent the solution from contacting the metal and the reaction will soon cease.
Steel wool will have a good surface area, but it can be difficult to separate the copper powder formed from the iron filings / rust from the wool. The
same problem occurs with the use of aluminum foil and small fragments of aluminum that are difficult to separate are produced.
The best way I have ever found to produce reasonably fine copper powder is to use a solid piece of aluminum to reduce Cu+ and add chloride ions to the
solution (which can be easily washed and removed from the final product at the end, along with all the others soluble contaminants).
I dont remember for sure the mechanism, but it seems that Cl- in the presence of ionic copper acts by removing the aluminum oxide layer and exposing
the bare metal, which in turn reduces Cu+ to the metal. I do this and the copper powder does not adhere to aluminum.
Bedlasky - 15-4-2021 at 11:20
Johnny Cappone: I did nickel by reaction of nickel sulfate and aluminium foil in the presence of NaCl (I determined purity by chelatometry - 93,78%).
I removed most of the aluminium by concentrated NaOH (I removed solution after several hours when bubbling stoped). But I want to use iron as reductor
- I have now just small amount of Mohr's salt, so this is useful byproduct for me.
Unionised: Good idea, I will buy some steel wool. Strange is that when I did this reaction in the past, iron nails were covered with fragile spongy
copper and not hard crust.
[Edited on 15-4-2021 by Bedlasky]
zed - 15-4-2021 at 12:02
Well, Ascorbic Acid reduces Copper Sulfate to metallic Copper.
I really should look up how that works.
But, regardless of my not quite understanding it, it does work.
And now, I'm going to go investigate how.
As a side note: Ascorbic Acid, also reduces Benzene Diazonium Salts... To Phenyl Hydrazines (or analogs).
Bedlasky - 15-4-2021 at 12:06
Iron or aluminium are much cheaper than ascorbic acid.
vano - 15-4-2021 at 21:45
yes aluminum and such metals are cheap, but i prefer organic compounds ascorbic acid, hydrazine solution and others.
XeonTheMGPony - 16-4-2021 at 03:44
I used citric acid and seemed to have reduced the copper sulphate back to metallic copper effectively
unionised - 16-4-2021 at 03:58
You can strip out excess iron with a magnet.
You can dissolve excess aluminium with NaOH
And you could remove either of then with dilute acid.
If you wan to go down the ascorbate path - which might make sense if you have lots of it- you need to know that it only works well in strong alkali.
It can be tricky to distinguish powdered copper from powdered Cu2O