Precipitating Silver with Aluminium

[AndreTrollip]

Hi guys,

First of all, thank you for a great forum. I have silently learned so much from you guys.

Now my question. I have substantial volume of silver nitrate from which I want to extract the silver. I see copper is commonly used to precipitate the silver out of solution. I happened to have a lot of Aluminum left over from another project. Can I use aluminum instead of copper?

Thanks in advance.

 

[4metals]

It all depends on what other metals are in solution with your silver.

The reason copper is preferred for cementation of precious metals is that it sits just above the precious metals on the electromotive series chart. In that position it will drop all of the precious metals and mercury from solution and nothing else. aluminum is pretty much at the other extreme of the chart. It will displace copper, lead, zinc, nickel, tin....... and the list goes on.

So if you have a solution which is pure silver nitrate, you can expect the aluminum to displace the silver from solution and you will have a pretty clean silver drop. If there are other metals in solution, good chance they're coming out with the silver and you will have a mess.

 

[AndreTrollip]

Thanks 4metals. That makes complete sense. I guess I'll use copper then.

 

[4metals]

It may help to print this chart out and paste it up on the wall in your refining area.

View attachment electromotive series.docx

 

[kurtak]

Aluminum will not cement silver out of a silver nitrate solution because even though aluminum is high on the reactivity scale it does not react with nitric acid

Kurt

 

[4metals]

Good point, I know people who use it to recover copper from spent aqua regia because they have it lying around. But in straight nitric, Kurt is correct, the aluminum will not dissolve. Aluminum passivates in nitric.

 

[Lino1406]

Precipitation from pure silver nitrate is best done by caustic soda (NaOH solution),
where the resulting silver oxide is directly taken for melting

 

[kurtak]

Good point, I know people who use it to recover copper from spent aqua regia because they have it lying around. But in straight nitric, Kurt is correct, the aluminum will not dissolve. Aluminum passivates in nitric.

Correct - it will work in HCl solutions to cement metals below it in the reactivity series - however the solution gets quite jellied (thick) so is hard to filter - zinc is a better choice - trade your aluminum at the scrape yard for zinc (die cast)

Kurt