Sciencemadness Discussion Board

magnesium from soda cans

ATPfactory - 10-9-2021 at 16:36

I was googling for new projects and I somehow landed on the composition of soda cans. Apparently there is 4,5%Mg 95,2%Al and 0,35%Mn in the top and bottom of the can and 1%Mg 97,8%Al and 1,2%Mn in the rest of the can.
So I thought, ok cool maybe I can extract the magnesium somehow.

The first few results from google told me that NaOH can dissolve aluminum but that it won't dissolve magnesium and manganese.

Does anyone know if this would actually work?

Yttrium2 - 10-9-2021 at 19:21

https://m.youtube.com/

watch?v=b0BcNodwK3A

[Edit by mod]
Link broken. Irrelevant.
Do not do this again, Yttrium. This is a violation of a recent mod warning. Banned for a week.
[/Moderation]

[Edited on 11-9-2021 by j_sum1]

Fulmen - 11-9-2021 at 02:41

Sorry, but that won't work. Magnesium reacts with water, so does aluminum. The NaOH just breaks down the Al's protective oxide coating, allowing it to react with water forming oxides and hydrogen.

night429 - 11-9-2021 at 09:09

Quote: Originally posted by Fulmen  
Sorry, but that won't work. Magnesium reacts with water, so does aluminum. The NaOH just breaks down the Al's protective oxide coating, allowing it to react with water forming oxides and hydrogen.


Isn't aluminum hydroxide/oxide amphoteric, though? It would form water-soluble sodium aluminate in the presence of excess NaOH. Manganese and magnesium would form insoluble non-amphoteric hydroxides.

Fantasma4500 - 19-9-2021 at 01:04

you could try burning it in nitrogen atmosphere, magnesium forms magnesium nitride, not sure about aluminium.

it seems solubility data for magnesium/aluminium salts are quite similar, you might have to find some data on seperating the salts with ethanol or similar solvent, acetone maybe
my take is if you have a practical purpose it just isnt worth it

NaOH with aluminium forms sodium aluminate
dont know about magnesium and NaOH
however, you could precipitate out the hydroxides, fry it in oven to acquire aluminium/magnesium oxide
the magnesium oxide should be rather soluble in acids where aluminium oxide is quite resistant

magnesium oxide as supplement barely has 20% bioavailability and theres HCl in stomach

aluminium carbonate cant exist, it decomposes into i believe aluminium oxide, but maybe hydroxide
magnesium carbonate can exist, and it reacts readily with acids

macckone - 23-9-2021 at 08:16

short answer is this proposal won't work.

longer answer is that if you want magnesium ions, just buy epsom salt or milk of magnesia.
magnesium ribbon is not 'cheap' but it is relatively easily available.

you can also buy magnesium anodes which are generally AZ31 - 97% mg, 3% al, 1% zn, 0.2% mn.
yes, I know that doesn't add up to 100%.
https://www.azom.com/article.aspx?ArticleID=6707


Depending on your application AZ31 may or may not be usable.

MidLifeChemist - 23-9-2021 at 14:00

short answer - this won't work. long answer, magnesium ribbon is very cheap to buy.

vmelkon - 24-10-2021 at 18:32

Quote: Originally posted by ATPfactory  
I was googling for new projects and I somehow landed on the composition of soda cans. Apparently there is 4,5%Mg 95,2%Al and 0,35%Mn in the top and bottom of the can and 1%Mg 97,8%Al and 1,2%Mn in the rest of the can.
So I thought, ok cool maybe I can extract the magnesium somehow.

The first few results from google told me that NaOH can dissolve aluminum but that it won't dissolve magnesium and manganese.

Does anyone know if this would actually work?


I don't know much about manganese but if you try this, the magnesium would react with the water and form Mg(OH)2. The Mn might end up as a fine powder.
I tried something similar except I used another alloy:
tin + silver + copper where silver and copper is <2% and put this in HCl.
You end up with a tin chloride solution and powdered copper and silver.

I am not sure but perhaps if you put this in HCl, you will get the chlorides.
Adding some NaOH might precipitate Al(OH)2, Mg(OH)2, Mn(OH)2.
I think heating the solution would dissolve Mg(OH)2 and then filter.



metalresearcher - 24-10-2021 at 23:47

Quote: Originally posted by vmelkon  
Quote: Originally posted by ATPfactory  
I was googling for new projects and I somehow landed on the composition of soda cans. Apparently there is 4,5%Mg 95,2%Al and 0,35%Mn in the top and bottom of the can and 1%Mg 97,8%Al and 1,2%Mn in the rest of the can.
So I thought, ok cool maybe I can extract the magnesium somehow.

The first few results from google told me that NaOH can dissolve aluminum but that it won't dissolve magnesium and manganese.

Does anyone know if this would actually work?


I don't know much about manganese but if you try this, the magnesium would react with the water and form Mg(OH)2. The Mn might end up as a fine powder.
I tried something similar except I used another alloy:
tin + silver + copper where silver and copper is <2% and put this in HCl.You end up with a tin chloride solution and powdered copper and silver.

I am not sure but perhaps if you put this in HCl, you will get the chlorides.
Adding some NaOH might precipitate Al(OH)2, Mg(OH)2, Mn(OH)2.
I think heating the solution would dissolve Mg(OH)2 and then filter.


Sn + Ag + Cu are much 'nobler' metals than Al and Mg, so this is not a fair comparison.

unionised - 25-10-2021 at 03:45

Quote: Originally posted by vmelkon  

I think heating the solution would dissolve Mg(OH)2


I don't.

macckone - 25-10-2021 at 08:09

MidlifeChemist,

Try buying a kilo of magnessium ribbon and tell me how cheap it is.
Buying it in bulk from rotometals is about $144 / kg plus shipping.

Morgan - 25-10-2021 at 11:19

Quote: Originally posted by macckone  
MidlifeChemist,

Try buying a kilo of magnessium ribbon and tell me how cheap it is.
Buying it in bulk from rotometals is about $144 / kg plus shipping.


Ebay has this listing.
Magnesium Rods metal Ingot High Purity 99.95% - 915mm x 35mm $93/Rod ($27/lb)

unionised - 25-10-2021 at 11:32

Quote: Originally posted by macckone  
MidlifeChemist,

Try buying a kilo of magnessium ribbon and tell me how cheap it is.
Buying it in bulk from rotometals is about $144 / kg plus shipping.

Quote: Originally posted by ATPfactory  
... Apparently there is 4,5%Mg 95,2%Al and 0,35%Mn in the top and bottom of the can...


How much would 22Kg of scrap cans cost?
Then there's the other costs.


I can buy Mg ingots at about£20 per kilo on eBay.

vmelkon - 26-10-2021 at 06:26

Quote: Originally posted by unionised  
Quote: Originally posted by macckone  
MidlifeChemist,

Try buying a kilo of magnessium ribbon and tell me how cheap it is.
Buying it in bulk from rotometals is about $144 / kg plus shipping.

Quote: Originally posted by ATPfactory  
... Apparently there is 4,5%Mg 95,2%Al and 0,35%Mn in the top and bottom of the can...


How much would 22Kg of scrap cans cost?
Then there's the other costs.


I can buy Mg ingots at about£20 per kilo on eBay.


I measured the mass of a drink called Bubbly, it is 355 mL can.
Bubbly 355 mL can mass = 12.89 g

In Canada, you pay 0.05$ when you buy and when you return, you get back the 0.05$.

22 kg / 12.89 g * 0.05$ = 85.34$ for 22 kg of cans
3.88$/kg

unionised - 26-10-2021 at 10:41

I'm pretty sure it would be $85.35 rather than $85.34
:-)
But that's pretty close to £50 (I'm assuming its Can adian $ ) to get my 1Kg of Mg (mixed in with the other stuff)
So I'm rather better off just buying the magnesium- though it may be less fun.

Fulmen - 26-10-2021 at 10:44

Quote: Originally posted by vmelkon  
3.88$/kg


That's for a kilo of aluminum alloy which will give you exactly 0g of magnesium metal.

macckone - 26-10-2021 at 13:13

Morgan,
Buying a bulk amount of solid metal will of course be cheaper.
You can buy 5 lbs from belmont for cheaper and a more reliable source.

Linus1208 - 26-10-2021 at 14:26

At first, I'm not sure that all soda cans consist of one alloy, I heard that some are made from tinplate (if I translated that correctly).

If it does, an approach would be to dissolve the cans in NaOH solution to get the Al out as water soluble sodium aluminate.

I'm not sure how the magnesium would react, probably it would form Mg(OH)2 mixed with unreacted metal.
The manganese will probably be present in a similar form, insoluble hydroxides and oxides, maybe mixed with some unreacted metal.

I don't know how you would seperate mangenese and magnesium, as mangese salts and magnesium salts with the same anion often seem to have similar solubilities.

Morgan - 26-10-2021 at 16:31

Quote: Originally posted by macckone  
Morgan,
Buying a bulk amount of solid metal will of course be cheaper.
You can buy 5 lbs from belmont for cheaper and a more reliable source.


Thanks for the Belmont source. I remember at one time ebay used to have huge ingots of magnesium for sale but not anymore I guess.

vmelkon - 30-10-2021 at 13:31

Quote: Originally posted by Linus1208  
At first, I'm not sure that all soda cans consist of one alloy, I heard that some are made from tinplate (if I translated that correctly).

If it does, an approach would be to dissolve the cans in NaOH solution to get the Al out as water soluble sodium aluminate.

I'm not sure how the magnesium would react, probably it would form Mg(OH)2 mixed with unreacted metal.
The manganese will probably be present in a similar form, insoluble hydroxides and oxides, maybe mixed with some unreacted metal.

I don't know how you would separate manganese and magnesium, as manganese salts and magnesium salts with the same anion often seem to have similar solubilities.


For sure, the magnesium would quickly react with the water and form Mg(OH)2 since it is a mediumy reactive metal.

I don't know what would happen to the Mn. Let's assume it will be in the form of Mn(OH)2.

You can filter and collect the Mn(OH)2 and Mg(OH)2. Add some HCl.
Perhaps doing some electrolysis of the solution of MgCl2 and MnCl2 would give you some Mn metal. This will remove the Mn2+

For the Mg, I guess you could melt the MgCl2 and do electrolysis but that is not simple for the home amateur.

MgCl2 mp = 714 °C
Density = 2.32 g/cm3
Mg mp = 650 °C
when liquid, at mp, Density = 1.584 g/cm3

so it looks like the Mg would be liquid, it would float on liquid MgCl2 and would contact the air.

Another solution would be to melt MgI2
mp = 637 °C
but it is difficult to have that kind of temperature control for the home chemist.

unionised - 31-10-2021 at 07:35

It's absurd but if you insist...
Dissolve the metal in excess NaOH solution.
The Al will dissolve as aluminate.
You can settle or filter out the hydroxides of the other metals like Mg, Mn etc.
Rinse them with water to get rid of excess NaOH etc.

Expose the mixture to air until the Mn oxidises to Mn(III) or Mn(IV)
Extract with a weak acid like acetic.
That will rapidly dissolve the Mg(OH)2 but won't affect Mn2O3.

So you will get a solution of the Mg as the acetate.
You can precipitate Mg as carbonate or hydroxide and then dissolve it in HCl to give MgCl2 which you probably won't be able to melt and electrolyse.

If you also want the manganese, reduction of the Mn2O3 with aluminium is an option, though I gather that's not a well behaved thermite.