3 ms·

Probably can't directly separate the elements in the melt here but I'm not an expert on melt processing/purification of aluminum. Certainly possible with other

by s0rce 2y ago

Probably can't directly separate the elements in the melt here but I'm not an expert on melt processing/purification of aluminum. Certainly possible with other methods but might not be economical.

kergonath 2y ago
We can have a look at phase diagrams for this. For example, for Fe-Al here: https://www.researchgate.net/profile/Qingyou-Han/publication/225778007/figure/fig2/AS:393820391919622@1470905506653/The-iron-aluminum-phase-diagram.png https://www.researchgate.net/profile/Qingyou-Han/publication... . This shows that Al with some Fe is in 2 phases when it is solid (pure Al on one side and FeAl3 on the other). However, above 660.452°C, there is only one liquid and Al and Fe cannot be separated. There is a tiny temperature range where there is a combination of liquid Al and solid FeAl3, between 655°C and 660.452°C, so completely impractical from an industrial point of view. That’s an example; it’s even worse with Al and Ni because even the solid is a mixture. I am less familiar with the Al-Co and Al-Ti phase diagrams, but looking at them Al-Co seems similar to Al-Ni and Al-Ti to Al-Fe. Multi-elements alloys would be a bit different but not too much: if everything is soluble in Al separately, then all of them at once are also soluble to some extent. In short, it might be possible to extract pure Al for recycling, but it does not seem to be easy and there would still be a lot of Al bound to the other metals in the waste.
- HPsquared 2y ago
  Ah, so that's why "irony aluminium" scrap (that is aluminium with iron in it, like an aluminium casting with steel bolts) has such a drastically lower value than pure aluminium scrap.
pfdietz 2y ago
They could probably be separated by distillation, but the temperature would be quite high. Alternately, maybe some element could be found that would preferentially dissolve aluminum (magnesium?) and that then could be separated, again perhaps by distillation. Al/Mg mixtures can melt as much as ~200 C cooler than pure Al.

by s0rce 2y ago

Probably can't directly separate the elements in the melt here but I'm not an expert on melt processing/purification of aluminum. Certainly possible with other methods but might not be economical.

kergonath 2y ago

We can have a look at phase diagrams for this. For example, for Fe-Al here: https://www.researchgate.net/profile/Qingyou-Han/publication/225778007/figure/fig2/AS:393820391919622@1470905506653/The-iron-aluminum-phase-diagram.png https://www.researchgate.net/profile/Qingyou-Han/publication... . This shows that Al with some Fe is in 2 phases when it is solid (pure Al on one side and FeAl3 on the other). However, above 660.452°C, there is only one liquid and Al and Fe cannot be separated. There is a tiny temperature range where there is a combination of liquid Al and solid FeAl3, between 655°C and 660.452°C, so completely impractical from an industrial point of view. That’s an example; it’s even worse with Al and Ni because even the solid is a mixture. I am less familiar with the Al-Co and Al-Ti phase diagrams, but looking at them Al-Co seems similar to Al-Ni and Al-Ti to Al-Fe. Multi-elements alloys would be a bit different but not too much: if everything is soluble in Al separately, then all of them at once are also soluble to some extent. In short, it might be possible to extract pure Al for recycling, but it does not seem to be easy and there would still be a lot of Al bound to the other metals in the waste.

HPsquared 2y ago
Ah, so that's why "irony aluminium" scrap (that is aluminium with iron in it, like an aluminium casting with steel bolts) has such a drastically lower value than pure aluminium scrap.

pfdietz 2y ago

They could probably be separated by distillation, but the temperature would be quite high. Alternately, maybe some element could be found that would preferentially dissolve aluminum (magnesium?) and that then could be separated, again perhaps by distillation. Al/Mg mixtures can melt as much as ~200 C cooler than pure Al.