WARNING: Sodium hydroxide and hydrochloric acid are corrosive, wear gloves when handling them.
Diethyl ether is highly volatile and highly flammable.
Work in a fume hood and fire safety protocols must be in place.
Greetings fellow nerds.
You've seen me destroy aluminum with gallium in various videos and some of you have asked how to recover it from the spent aluminum.
In a previous video i showed an easy method using sodium hydroxide decomposition that essentially destroys the aluminum but leaves the gallium behind.
You can check the video description for that video.
Now this method does work and for the amateur this is probably all you need.
But a lot of the gallium is destroyed as well so recovery isn't very good.
In this video we're going to use a solvent extraction method to recover even more gallium.
The idea is that we're going to selectively dissolve gallium chloride in diethyl ether but not aluminum chloride.
This allows us to concentrate the gallium for easier recovery.
To show you how effective this is, i'm going to use the spent waste from the previous video.
It's looks like a great deal more than what i had in that video because this also includes runs which didn't work.
Now we already removed the recoverable gallium from this so this should be depleted.
Let's see how much gallium we can recover with this solvent extraction method.
Now this waste is mostly aluminum oxide as well as sodium hydroxide and tiny amounts of gallium hydroxide.
First we'll need to neutralize all of it with concentrated hydrochloric acid.
It's bubbling because it's releasing carbon dioxide.
It absorbed a lot while sitting at the back of my lab for the past couple of months.
What we want is to convert all the metal oxides and hydroxides into their chloride salts.
Aluminum, gallium and sodium chloride.
Keep adding hydrochloric acid until it stops bubbling.
It's not clear yet because at room temperature the conversion to aluminum and gallium chloride is rather slow.
Transfer the mixture to a glass container and heat it on the hotplate.
As it heats up it will drive the reaction forward and clear up.
If the solution boils but is still not clear then you'll need to add in more hydrochloric acid.
The yellow color you see here is iron contamination.
Aluminum metal tends to have very tiny amounts of iron in it.
It's not a problem for most purposes but iron chloride will give a strong yellow color like this.
Anyway, once everything is dissolved let it cool.
Now as it cools it may crystallize out excess aluminum and sodium chlorides.
This is not a problem is what we really want, the gallium chloride, will remain in solution.
Now filter out the mixture.
This is to get rid of the crystallized salts and also to get rid of the various paint chips that came with the aluminum softball bat we originally performed our experiment on.
And here we have it a solution of aluminum and gallium chlorides.
Now place this in the fridge and cool it down further.
We're doing this because we'll be performing a solvent extraction with ether later and a cold solution will help prevent evaporative losses.
And here we are after leaving the solution in the fridge overnight.
You can see even more of the aluminum chloride crystallizing out.
Now you're going to need a large separatory funnel.
We fill it halfway, in my case 500mL, with diethyl ether.
I got most of mine distilling it off starter fluid as shown in a previous video.
Diethyl ether has a low boiling point of just 34.6 degrees celsius so on a hot day like today you can lose a lot just from evaporation.
It's also a tremendous fire hazard being so volatile and flammable.
So when doing extractions, it's a good idea to pre-chill it in the fridge if you can.
This helps to keep the vapors under control.
Okay now that the ether is in there, we add the solution of the aluminum chloride.
Once it's in there, put the cap on and shake it up to perform the extraction.
Now this is where the actual important part is happening.
Gallium and aluminum chlorides are both highly soluble in water.
But gallium chloride is also soluble in diethyl ether.
So by shaking them together we can transfer gallium chloride from the water to the ether and leave behind aluminum chloride.
This allows us to tremendously concentrate and purify the gallium from the aluminum.
Okay, after a few minutes of shaking.
Let the contents settle and drain out the bottom aqueous layer this should be depleted in gallium chloride.
Keep the upper organic layer of ether.
Now i have a lot more solution so now i'm going to add another 500 ml of it to the ether and extract more gallium chloride.
Now you professional chemists are probably yelling at the screen right now.
Extracting it this way is not as efficient as using fresh ether with fresh solution.
I'm doing it this way because this is all the diethyl ether i had so i have to reused the same amount.
I'm not going to recover all the gallium possible but at least we'll have enough to demonstrate the process.
Anyway, once again drain off the aqueous layer and extract more solution until you've gone through it all.
And here it is, a solution of ether and gallium chloride.
The yellow color is from small amounts of iron chloride which is also slightly soluble in ether.
Now we need to remove the ether.
Simply set up for distillation and distill it off.
Stop distilling when no more ether transfers over at its boiling point.
You can actually reused the ether and extract again the aluminum and gallium solution for maximum recovery.
I didn't do that because i didn't have the time.
Now I went a little too far in my distillation and charred my residue but this isn't a problem.
Now at this point we have a syrup of gallium trichloride, residual water and ether.
Gallium chloride actually binds ether pretty strongly so distilling it off is actually pretty hard.
We need to get it back into water solution so add in about twice its volume of water.
The separation of layers shows that the ether wasn't fully distilled off.
Just put it back into distillation and distill off the ether until water starts distilling.
The ether now distills off easily because the gallium chloride can bind with water instead of ether.
Now at this point we have a solution of gallium trichloride in water.
Now add in small amounts of sodium hydroxide.
About five percent of the solution mass at a time.
At first it will form a precipitate of gallium hydroxide.
But as you keep adding sodium hydroxide it will dissolve again as the sodium hydroxide and gallium hydroxides react to form a sodium gallium hydroxide.
It is this stuff that we want so keep going until the precipitate dissolves again.
Now at this point i made a major fail.
I added too much sodium hydroxide at once at the solution go so hot that it boiled over.
All that work destroyed in the blink of an eye.
This was the kind of mistake i yelled at my students for doing back when i was a chemistry TA.
Now people keep telling me to post my failures so you can learn from them.
All you're really learning from this is that i am an idiot.
I'm certain you already knew that a long time ago.
Anyway there is still a small amount left that we can still work with so i'm going to clean up and keep going but we're going to have very bad gallium recovery.
Here is the solution with all the gallium hydroxide redissolved.
I added a bit of water so i would have more volume to work with.
The black suspension is iron hydroxides that also precipitated out and did not redissolved.
Now i wanted to filter them out but they passed right through my filter paper.
I don't have a finer filter so we're just going to have to go to the next step anyway.
Now to recover the actual gallium metal we set up for electrolysis.
On the right over here is a platinum anode.
You can also use nickel since we're working in strongly alkaline conditions.
On the left here is a titanium cathode.
But you can also use copper, nickel, steel and most other metals that are stable in alkaline solutions.
Now we run enough current until the cathode just starts to bubble.
This is where we're producing gallium metal.
At the anode we're mostly generating oxygen although there will be some chloride electrolysis as well.
The whole solution is being gently heated to 40 degrees celsius so the gallium actually drips off the cathode as a liquid.
The suspended iron particles are blocking our view which is why i wanted to remove them.
But you can make out droplets of gallium metal forming.
I think it's amazing to actually see a liquid metal electrolyze out of solution.
Now you might be asking why we didn't do the electrolysis on the bulk waste.
This is because the gallium concentration is far too low.
We need the solvent extraction to separate and concentrate the gallium so that it could be recovered by electrolysis.
Anyway, keep electrolyzing until no more gallium deposits out.
And there we have it.
Gallium metal recovered by solvent extraction and electrolysis.
It doesn't look like much, but keep in mind that this was what the sodium hydroxide method could not recover, this was done on the waste.
And this experiment was also a failure.
If a failure gives results this good, imagine how much I would have gotten if I actually did this right.
For comparison this is the same gallium nugget recovered by simple reaction with sodium hydroxide.
I think i would have gotten an equal amount if i hadn't screwed it up.
So when recovering gallium, you have two options.
You can use sodium hydroxide reaction as shown in a previous video which is quick and easy.
But if you're willing to put in the work.
You can instead react your aluminum metal with hydrochloric acid and use solvent extraction with ether as shown in this video for vastly improved recovery.
Assuming of course you don't mess it up like I did.
Thanks for watching.
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