getting Al the electrolytic way?

[-A-]

I didn't find this with the search. It can get a little boring sanding the aluminium, so I started searching for a better method. So I begin wondering if Al could be obtained using electrolysis.
Let's see, if you dissolve Al foil in HCl, you get AlCL3, don't you?. Well I discarded this as AlCl3 is far too dangerous. So, using a safer salt, e.g. aluminium sulphate, is it possible to get aluminum using electrolysis?.

[Mr Cool]

Yes, it'll get you Al. You'll need to melt the salt at about 1000*C. Obviously you'll have to do the whole thing in an argon atmosphere so that the Al doesn't burn as it's made. The power supply is simple - 12V at a few amps should work, so a car battery could be used. But when you've finished, you'll have a block of Al, which you'll still need to sand down.
If you do it in water, you'll only get Al(OH)3.

[Anthony]

If you have two Al electrodes and strike and arc between them under water you'll get fine Al powder.

[-A-]

Anthony, by striking an arc between them, you mean a current? (I am not a native english speaker).
But, I don't understand how I would be able to get aluminum powder that way... also, wouldn't the fine Al powder get oxidized under water?

[Mr Cool]

The powder will be reacted and made useless by the water, I'm sure of it.

Edit: but maybe you could do it under oil?

[This message has been edited by Mr Cool (edited August 17, 2001).]

[Anthony]

I've done this in a beaker using Al foil eletrodes (crumbled up), I was only using 12v so I couldn't produce an arc between them so I just stroked them together. It definitely produced a powder.

I just used straight tap water, but boilign the water would remove all dissolved oxygen and things can't oxidise without oxygen!

By Arc I mean a continuous electrical spark that jumps a gap between two electrodes.

[-A-]

<font face="Verdana, Arial" size="2">Originally posted by Anthony:
I've done this in a beaker using Al foil eletrodes (crumbled up), I was only using 12v so I couldn't produce an arc between them so I just stroked them together. It definitely produced a powder.

I just used straight tap water, but boilign the water would remove all dissolved oxygen and things can't oxidise without oxygen!

By Arc I mean a continuous electrical spark that jumps a gap between two electrodes. </font>

Mhhh, strange procedure, never heard of that before. I will give it a try. However, the part where you talk about removing dissolved oxygen from water... can´t the Al get oxidized just from the water?. It looks like I have a fault in my chemistry knowledge...

[J]

The water will decompose into Hydrogen and Oxygen. Perhaps the powder was Al2O3?

J

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[Mr Cool]

No oxygen needed to fuck things up:
2Al + 6H20 --> 2Al(OH)3 + 3H2

I'm afraid your powder was probably a hydroxide. But I can't see why it wouldn't work under an oil of some sort if it makes a powder.

[-A-]

This procedure is intriguing me. I will definitely give it a try, but not under water for sure.

[kingspaz]

also AlO3 will be produced because of electrolysis producing oxygen.

edit. sorry J didn't realise you said the same thing.

[This message has been edited by kingspaz (edited August 19, 2001).]

[Anthony]

The idea originally came from NBK2000 (IIRC)

I can't see I tried the procedure extensively (in fact I threw the "Al" away with the water as progress was very slow).

So it might have been something other than Al. But I know that steel stored under boiled water will not rust (one of the few text book experiments I remember from school). So if the water does not decompose, why should the Al oxidise?

[Lagen]

I dare to say that the "striking an arc between aluminum electrodes under water" method works. This was the standard industrial method for making Al powder before the advent of vacuum vaporisation. The powder thus obtained is called "colloidal aluminum". The aluminum will not completely decompose into Al(OH)3, just as an aluminum cup doesn't decompose in water. There is a thin layer of aluminum hydroxide and oxide forming on the particles that prevents further oxidation. The thickness of the layer depends on the speed of its formation. Under water a thin layer forms which is good. kingspaz: Electrolysis plays a minor role here, if there is a true arc!

Edit: Sorry kingspaz, I confused you with someone else!

To make it clearer. I don't advocate "getting Al the electrolytic way". Anyone that seriously believes he can get powdered Al by electrolysing AlCl3 in a water solution or by AlCl3 + Mg (crapbook method) either is a moron or hasn't seen the electrochemical series. In the electrolysis the Al is formed as single atoms and these will be 100% reacted. In the arc, however, small droplets (hence the name "colloidal") of molten aluminum form, the rest is obvious, this is physics, no chemistry or electrochemistry ...

[This message has been edited by Lagen (edited August 19, 2001).]

[firebreether]

I would have thought that the Al would have been plated on the - electrode similar to electroplating gold onto jewelry

[Mr Cool]

I just assumed that since the particles would probably be hot when they touched the water, and they're very small, that they'd be corroded so much that they'd become useless.

[Lagen]

Aluminum cannot be plated in water! Again, it's a matter of oxidation potentials! The only (at least a bit common) metals that can do the trick are: platinum, gold, silver, mercury and copper.
Mr Cool: I admit I have not tried this. But it's not from my head, I've been told by others, that really know their stuff. So I think it's not complete BS. But I'm sure there will be losses (smaller particles will surely oxidize, the resulting powder will contain particles of variable size ...). If the process gave a perfect product it would not have been abandoned. If someone wanted to try it, making the arc is easy with minimal equipment, if you wish, I can post some instructions...

[nbk2000]

I used the arc process for copper. It's important to use distilled water to prevent electrolysis.

If the aluminum is oxidized (very likely), one could take the ultrafine powder, place it in a class tube, start a flow of hy7drogen gas through the tube, then heat to redness to reduced the oxide to the base metal. This is the process they originally used.

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[Mr Cool]

Hydrogen reducing Al2O3? Sounds unlikely to me.

[Lagen]

I am sceptic on this, too. Aluminum replaces hydrogen in compounds, not the other way round. But for removing oxide layers from copper, it would work well.

[-A-]

First, I haven't said water is the only solvent you can use... If you make electrolysis under water is obvious the Al will get oxidized. That's why am asking of another method or solvent for the electrolysis.
However, if the arc method works, why does it has to be made under water?. Can't you use another liquid that doesn't oxidize the Al?.

[PHILOU Zrealone]

Think a bit!
2Al + 3H2O + heat or no if the metal has a high specific surface (or a very thin oxyd layer) --> Al2O3 + H2 + a lot of heat! Thermodynamicly and chemicaly reduction of Al2O3 is not possible from H2!

Seems to me I have enough exposed in the past ways to make fine Al powder so do a little search.
Again and it is borring to write this for the 4th time for further explanation SEARCH IN THE PAST: Explosion of Al electrodes in cold inert gas like Ar or He or Ne (N2 might be considered but produces a bit of AlN)...then slow introduction of cold air...the colder the thiner the oxyd layer...you end with very reactive Al powder (over 1000 mesh).


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