Sciencemadness Discussion Board

First Run: Purification of Aluminum

theDudeintheHat - 8-3-2014 at 14:52

Hey all, I've just recently introduced myself to the wonderful world of science after several years of learning it in school and some research in the wonderful world of Google. Right now. Other than a few flasks and a scientific calculator I only have rudimentry tools until i get some actual lab equipment (a .01g scale and some graduated cylinders to begin with), but I have come up with a question that I cannot seem to find a Direct answer for... How can I purify Al2 from scrap aluminum with unknown contaminents? After that, how could I purify Cu?

I have a chunk of an old radiator waiting to be ripped down and sent out to the scrap yard, and thought that instead of spending the next two days working on it, busting my knuckles. ect., there's got to be an easier way... NaOH!

Just for kicks I decided to prepare a concentrated (but not saturated) solution of NaOH to which i added the contaminated Al and observed the reaction. I have to wait until I get the tools to measure weight and volume to actually calculate M but I could use a little help with the theory. The Reaction so far:
NaOH(aq)+Al(s)-->Al2(OH)3(aq)+H2(g)
After this, im lost as to what to do next... In the Bayer Process, the solution is filtered before CO2(g) is bubbled through it, precipitating out Al203, right? http://www.elmhurst.edu/~chm/vchembook/327aluminum.html

But other sources state that the reaction goes as follows:
Al2O3 + 2 NaOH + 3 H2O → 2 NaAl(OH)4
2 NaAl(OH)4 + CO2 → 2 Al(OH)3 + Na2CO3 + H2O
2 Al(OH)3 → Al2O3 + 3 H2O when heated to 980*C
http://en.wikipedia.org/wiki/Bayer_process
But from there, I add more heat to decompose the oxide into Al and 02(g)?

Which, if either, is correct/feasible? Or, is there an easier/better way of extracting pure aluminum from the contaminated alloy?
:(

*BTW, the reason I thought of NaOH over H2SO4 was to dissolve the Al without dissolving the Cu, then reacting the copper alloy with H2SO4 to yield Copper (II) Sulfate

plante1999 - 8-3-2014 at 14:56

It is gonna be harder then that, aluminium needs a lot of energy to extract, something that can hardly be done at home. You could turn it to aluminium sulfate at best.

theDudeintheHat - 8-3-2014 at 15:34

Would simply melting the aluminum fins with borax be a better route then? And what about the copper? What about the process won't work, which step is the most difficult and how can I go about trying it? I seem to learn more from my failures than successes. And please, excuse my ignorance, as I know only a little about metalwork, and less about metallurgy. I decided for my first couple of experiments to purify/collect my own elemental metals as well as learn how to turn what I have into what I can experiment with... Like all college students I only have access to what I have and what Home Depot can give me (cheaply of course). I know it is a basic and foolish way to start but I have decided to start with what I can do... Au is on the top of my list, but I'm gonna need more than just a mason jar and a hotplate for that.

Oscilllator - 8-3-2014 at 15:49

Any practical purification of aluminium is going to involve very high temperatures, so for a first experiment its a pretty bad idea. If you are dead-set on purifying a metal, you could try to purify copper.
One way would be to purify by electrolysis of CuSO4. Another would be to displace the copper with zinc or a similar reactive metal.
To start you off in the right direction, I recommend watching the videos posted by "nurdrage" on youtube.

Also regarding melting aluminium under borax, I'm not sure what that would achieve other than contaminating the aluminium even further. Having said that, if you can melt aluminium you should as it is great fun!

plante1999 - 8-3-2014 at 15:55

I would recommend you to start with copper, it is a quite noble metal (not much reactive), as such, it is easy to work with and require a lot less energy then active metals like aluminium.

Zinc could another idea.

theDudeintheHat - 8-3-2014 at 16:28

I want to play with zinc as well, but that's a little lower on the list. Is there anything I can do with the Al hydroxides, chlorides, sulfates, ect. that is fun/worthwhile without delving into electricity? Could I use them to precipitate/isolate other metals on the list? And what would be a good way to seperate the Cu from the copper-lead-tin-whatever alloy?
H2SO4+alloy-->CuSO4(aq)+PbSO4(s)+other impurities?

plante1999 - 8-3-2014 at 16:38

Does not work like that. You will have to read a bit more about chem. Not all metals react similarly, copper, lead, and many other metals do not dissolve in sulpuric acid. Nothing to do with aluminium compounds at your skills level.

theDudeintheHat - 8-3-2014 at 17:05

I havent experimented with anything other than what my chem class allows me to yet :( Im past most of the basic safety and calculations, and am now learning more advanced equations and laws, but I lack practical/lab time (most of it spent on the basics like, more recently, the dehydration of CuS04, B.P. elevation, F.P. depression and clock reactions). I want to try some more advanced experiments, and thought that seperating these two pieces of scrap should be fairly simple. What should I try next then?

plante1999 - 8-3-2014 at 17:10

Buy some malachite mineral on ebay, a small cubic inch should be enough, and try to get the copper out of this ore. It should be quite hard for you, but it is doable. Malachite is a "variety" of copper carbonate.

http://www.ebay.ca/itm/74g-Natural-Azurite-and-Malachite-Cry...

http://www.ebay.ca/itm/Rare-Malachite-Rough-Healing-Stone-Sp...

[Edited on 9-3-2014 by plante1999]

theDudeintheHat - 8-3-2014 at 17:32

Wonderful! I still want to construct a simple baking soda/vinegar reactor to bubble CO2 through the concoction I made today (once decanted and filtered, of course) just to see if anything precipitates out, even if I get nothing out of it, since I have to wait for everything I bought to ship anyway. Is there anything I could do with the H2 gasses when I saturate my solution to an excess of NaAl(OH)4, at my skill level, anyway?

plante1999 - 8-3-2014 at 17:34

Burn it for heat, else then that it need expenssive catalyst, it was not the best start sadly, but it how we learn isn't it?

theDudeintheHat - 8-3-2014 at 17:54

It always starts with a question, and those questions usually get me to learn what I can't do or how not to do it lol But hell, I could always hook it up to the lawnmower, its starting to feel like springtime again. http://www.youtube.com/watch?v=lKX_4feFLnM

Sedit - 8-3-2014 at 18:03

Are you just trying to separate the Copper from the Aluminum in order to get a higher price then just selling it as ACR scrap? If so I can assure you that mechanical separation is the way to go and I could help you with that if needed as I have been scraping my entire life.

Hell my first play house as a kid was built by money made from scrap metal and I now run a business doing just that.

plante1999 - 8-3-2014 at 18:06

You could, although it may be dangerous, be careful as always with chemistry.

theDudeintheHat - 8-3-2014 at 18:15

That's what its been sitting around for, i just havent had the motivation to go freeze my a** off, so I put it off for warmer weather, but I had the question of an easier route... And yes, I'd rather waste some spare time to get the higher price of the copper once its separated. I just had the thought that there might be all of $2.50 worth of alum. on it, so why not dump it in a bucket (so to speak) and dissolve it off and take the copper to the yard... but again that got me wondering if and how i could purify them (via experimentation) so that I have more pure reagents to experiment with! Until I hit this brick wall, of course. BTW, The only pure copper I have found on the interweb, other than copper strips of course, is a 1lb ingot of .999 pure (stamped and everything) investment/labratory grade for $30+shipping. I'm sorry, but I can't justify paying 10x scrap value for something I don't really need.

plante1999 - 8-3-2014 at 18:18

Copper wire is generally highly pure as impurity reduce electrical conduction.

You could probably make alum with it, I think mrhomescientist did a video about that.

Sedit - 8-3-2014 at 18:47

Use a sawzall with a very rough wood blade and run it along the top of the aluminum. It will shread the Al off and leave you with copper. Its relatively easy compared to Chemical separation of which I have tried it all.

Perhaps a NaCl/CuSO4 bath could be useful as it would also produce Cu during the reaction but mechanical separation is still tops trust me on that.

theDudeintheHat - 10-3-2014 at 10:57

My first try with a sawzall over the summer cut into all the copper i was trying to save... but then again that was with a metal blade. My thought was to put everything into a tub and soak in lye, bc as far as i can tell there is not much of a reaction on the copper, but that is where i got suck... if i cant do anything with the aluminates, then its not worth it at all. ideally, i want to turn a metal into a salt (or two, or three) then back into a metal, it doesnt matter what i start with as long as its relatively easy to procure. maybe ill start a new thread about it but i would like to do a relatively simple and reversible reaction { Ab+Cd-->Cb+Ad, Ad+Eb-->Ab+Ed } where i react a compound, then turn the new product back to the original compound later, like with the purification of gold, but with less dangerous reagents.
*aside, do you know how many vidoes of uninformed/uneducated people are on Youtube playing with aqua regia using measuring cups and camp grills?

blogfast25 - 10-3-2014 at 11:37

Quote: Originally posted by theDudeintheHat  
*aside, do you know how many vidoes of uninformed/uneducated people are on Youtube playing with aqua regia using measuring cups and camp grills?


Far, far too many.

MrHomeScientist - 10-3-2014 at 12:24

As Plante mentioned, I do indeed have a video on making alum from scrap aluminum (soda cans, in my case): http://www.youtube.com/watch?v=WAjrjY-JQ3o . Dissolving in base first serves to separate out much of the impurity metals that aren't amphoteric like aluminum. You can grow beautiful large crystals with this type of alum.

As for getting back to the starting metal, it's exceedingly difficult for aluminum. It takes large amounts of energy since it's really quite a reactive metal. There's a reason that it used to be more expensive than gold! According to wiki, aluminum production alone now consumes 5% of the electricity generated in the US.

It would be more practical to start with less reactive metals like copper or silver. I like the idea to smelt copper from malachite, and I've been wanting to try that myself for quite a while. The 'silver tree' experiment is a fun one to get silver crystals. Elecrolytic refining would be the penultimate purification step for most metals, but I've never tried this myself.
It's great to have grand ideas and even better to consult with those who have already tried these things, before starting down that road yourself :)

theDudeintheHat - 12-3-2014 at 18:25

The 'silver tree' looks pretty neat, I might try that one while I'm waiting for my new stuff to ship. I found another post on refining AgNO3 from scrap silver, so that'll be a great lead- in... I can take some scrap silver, treat it with nitric, then grow those neat crystals with some of it and heat the rest to decompose it. Impure metal->Metallic salt-> Pure Metal, I never though that silver would be simple and aluminum so complex! Now I just gotta figure out how to make nitric. I have a base idea but does it have to be very concentrated (vacuum distillation?) or could it be weak if I factor the molality?

theDudeintheHat - 12-3-2014 at 18:48

And that video looks oddly like the bayer process where adding acid causes the al(OH)3 to drop out of the system, but what was the final product, potassium alum or Al2(SO4)3?

MrHomeScientist - 13-3-2014 at 05:52

Potassium alum. Because I used KOH as the base and H2SO4 as the acid, the final solution is a mix of K+, Al3+, and SO42- ions. These come together to form the double salt KAl(SO4)2, which precipitates first.

There's tons of videos on nitric acid preparation. NurdRage has a very good guide to a few different routes. I've got a video as well: https://www.youtube.com/watch?v=PYDFplw8iKg . The sulfuric acid you use does need to be concentrated, but vacuum distillation isn't required. Without vacuum you can still produce red fuming nitric acid (RFNA), like I did. That's concentrated enough for anything I plan on doing, and the NO2 contamination that makes it red doesn't interfere with anything I use it for. If you can get some scrap silver, trying to purify it is a great learning experience. I've got a sterling silver chain that's broken that I'd like to try my hand at refining, just for fun.