Submitted by RestrictedCervical t3_10mw1j5 in explainlikeimfive
We use it for foil, cans, and so much more. Is it so plentiful it isn’t a concern? Or, do we reuse it very well?
Yeah, it's as common as dirt, literally.
While it's incredibly expensive to refine from the earth is 100% recyclable. You don't lose anything when you melt recycled aluminum.
This is correct for most uses however as I understand it aerospace applications always require virgin (ie not recycled) aluminum because during the recycling process a small amount of iron will contaminate it and because iron is soluble in melted aluminum is practically impossible to remove. This is not a problem for aluminum cans and most other uses but for aerospace applications that use very high-grade aluminum this is not acceptable.
Aluminum is one of the few things it is 100% unquestionably better to recycle.
How is that possible? There has to be some sort of loss. 100% is 100%.
Aluminum is an element. The aluminum stays aluminum forever. You may have some “loss” by having it drip out of a melting vessel or something like that, but 100% of the aluminum still exists. Just sweep it up when it cools and put it in the next batch.
Surely you'd have some sort of back reaction to AlO2. I work in primary aluminium production a few certainly have issues with back reaction.
Yeah, I don’t know what I’m talking about. Just sounded good to me at the time.
I would have figured there would be vapor loss during the heating.
Not really vapor loss, but there typically is some loss to oxidation. Alu binds very tightly to oxygen, which is also the reason why it takes so much energy to refine from ore in the first place. Aluminium exposed to air instantly forms a thin oxide layer, which is a bit more difficult to recycle than "just melt it". Pretty sure even this oxide dross is worth recycling though, it's basically very high grade ore.
how do u separate it? skim it out?
Actually yeah, it's that simple. Like say you take some aluminum cans and melt them in your backyard. Some of the inks and plastics burns off from the heat. The oxides float up to the top and you can scoop them out. What you pour out after is basically clean aluminum. Big industrial process are bigger, but functionally the same. They just pay a bit more attention to not letting oxygen contact the molten aluminum to prevent unnecessary oxidation. There are still some non aluminum impurities that get in there so you can't make a lot of alloys out of it, but it's plenty fine for lots of purposes like aluminum foil and cans and stuff that aren't like making up the wing of an airplane.
The dross you skim out is mostly it's aluminum oxide, but also contains a large amount of metallic aluminum that followed along for the ride. Depending on the initial melt composition and handling it can contain anywhere from 15%-85% recoverable aluminum. That can be recovered by mixing it with molten salt fluxes. This allows the metallic aluminum to separate out while the oxides mix in with the salt in a separate layer. You get an even worse grade of aluminum out due to the large amount of flux used, but again it's still useful for lots of stuff and the whole melting process takes something like 90% less energy vs processing raw aluminum oxides. The extra contamination from the salt flux is why you don't just toss in a bunch of salt in the first place.
Afterward once the salt is loaded up so much that it isn't useful as flux anymore is allowed to cool and is pitched as trash. It's called salt cake, and is actually a decent bit hazardous. Disposing of it safely is kindof becoming a problem actually.
Even if there was vapor loss, that vapor is still aluminum atoms. They'll condense somewhere and still be aluminum. So the amount of aluminum on Earth stays the same no matter how much we "use". I think that's what they're getting at with "100% recyclable".
The 100% isn't talking about getting all of the aluminum from, say, a can that you process, back from that processing, but that you can take that aluminum even with losing some of the raw material and shape it into cans that will be structurally no different from an aluminum can that was made from freshly-refined bauxite
Anything structural requires new aluminum. Including cans.
Scrap aluminum is actually mostly used as an oxidizer for steel production. They add it to the pot and it pulls all the impurities to the top.
Refining metals is a dirty business.
> While it's incredibly expensive to refine from the earth is 100% recyclable.
Huh?
Processing ore to produce aluminum is expensive.
Recycling (remelting) aluminum is easy and rather inexpensive.
The original poster is missing an "it" before the "is", but that shouldn't render the sentence incomprehensive.
It did for me.
Both.
Earth’s crust is 8% aluminum, so while there are certainly easy and hard sources to tap it is also the most common metallic element available.
We also recycle it in large volumes because it’s easy to rework and cheaper to rework than extract new.
To add to this, despite being in 8% of the Earth's crust, aluminum used to be very rare in it's natural state. Producing aluminum from ore used to be so difficult that it was more expensive than silver.
When the Washington Monument was finished in 1884, they placed atop it an aluminum primid lighting rod. It was the largest single piece of aluminum cast at the time. 2 years later the Hall-Héroult process was discovered, which allowed aluminum to be made quite cheaply.
I vaguely recall seeing a museum exhibit on cutlery. When royalty had guests, they brought out not silverware but the aluminum-ware.
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Let’s put it like this:
It is abundant… but…!
But it’s one of the metal the loves the most to oxidize and react with all sort of things in nature. Once you make it pure, it stays pure and does not corrode past its surface, In nature however, it is four mixed with all sort of things to which it loves to stick.
So the process of getting new aluminum requires to melt and process a lot of rock, discarding the most of it and keep some aluminum oxide. This requires to melt a lot of stuff. Then you have to convince that oxide to let go the oxygen it loves to stick to, so you can get pure aluminum. This requires a lot of electricity.
Basically finding aluminum is not an issue, but the amount of energy needed to purify it (read it as coal, gas, oil to burn to get that energy) is very big.
Mostly correct, although the part about pure aluminum not corroding is absolutely incorrect. Pure aluminum corrodes very quickly, but it's oxide doesn't flake and fall off like rust on iron. The outside of pure aluminum quickly corrodes in our atmosphere creating a very thin skin of an aluminum oxide. This thin layer provides a barrier that prevents oxygen from getting further into the aluminum and corroding the interior.
Ty, corrected. I skipped that cause I wanted to keep it short. I work in aviation and if I open my mouth about corrosion it can take few hours before I shout up again XD
Basically the method for extracting aluminium from raw ore is the same way as recycling it except that recycling contains a much purer form of aluminium and produces less waste so it is a lot cheaper to process recycled aluminium than to extract aluminium from aluminium oxide or bauxite.
Yes. For one thing, aluminium is one of the most common elements on Earth. Secondly, while it's a lot of effort to refine (In fact, before the industrial revolution, it was so expensive that Napoleon had aluminium tableware to flex on everyone who could only afford gold), aluminium, like most metals, can just be melted down and reused.
Both! Aluminum is extremely common and it's readily recycled!
The reason that we recycle so much of it is because it's actually cheaper and easier that making the new stuff.
If everything was like aluminum, it would go a long way to solving sustainably issues.
Aluminum is stupidly common. You know rocks? Aluminum is a significant fraction of the mass in rocks.
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Target880 t1_j65ic8d wrote
If you look at the abundance of elements in earth's crust aluminum is #3. It we use the CRC number from https://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth%27s_crust we have
So there is an enormous amount of aluminum. Most of it we use are in the for mof bauxite that is aluminum o
Aluminum is also recycled to a high degree. The primary reason is not the availability of bauxite ore. The primary reason is that the energy required to of recycling is 5% of the energy required to make it from ore. Aluminum requires a huge amount of electric energy to refine.
36% of the aluminum produced in the US comes from scrap. Globally the recycling rate is around 76% and it is estimated that 75% of all aluminum ever produced is still in usage.