Goofs by a famous person

[scrinch]

Quote:

Originally Posted by ERD50 1) "Aluminum is the most abundant metal on the planet" - OK, that is true, but it's not the whole truth. Like hydrogen, almost all aluminum is bound up with other elements. We don't come across a 'vein' of aluminum like we do coal, gold, silver or lead, etc. It takes a large amount of energy to break that bond and make useful aluminum. That is why it is important to recycle it - melting it and reforming takes takes far less energy than refining it in the first place. So not a goof, but a lost opportunity, and maybe misleading to a lot of people. -ERD50

Assuming that what is meant by "on the planet" really means "in the planet", aluminum is nowhere near the earth's most abundant metal. It is the crust's most abundant metal, but the crust represents less than 1% of the volume (and mass) of the earth. In the bulk earth, magnesium is the most abundant metal by molecular abundance, and iron is the most abundant by mass. Magnesium is stored mostly in the mantle in silicate minerals, and iron is mostly stored in the core as an alloy with Ni and other heavy elements. They are both more abundant than aluminum by a factor of 10-20x (depending on whether we are talking about molar or mass abundances). Aside from iron in the core, the overwhelming majority of all elements in the earth are bonded ionically or covalently within minerals, and when geochemists talk about abundances, we always refer to bulk abundances, not abundances of free, unbonded elements, of which there are almost none.

[38Chevy454]

Quote:

Originally Posted by scrinch Assuming that what is meant by "on the planet" really means "in the planet", aluminum is nowhere near the earth's most abundant metal. It is the crust's most abundant metal, but the crust represents less than 1% of the volume (and mass) of the earth. In the bulk earth, magnesium is the most abundant metal by molecular abundance, and iron is the most abundant by mass. Magnesium is stored mostly in the mantle in silicate minerals, and iron is mostly stored in the core as an alloy with Ni and other heavy elements. They are both more abundant than aluminum by a factor of 10-20x (depending on whether we are talking about molar or mass abundances). Aside from iron in the core, the overwhelming majority of all elements in the earth are bonded ionically or covalently within minerals, and when geochemists talk about abundances, we always refer to bulk abundances, not abundances of free, unbonded elements, of which there are almost none.

Also, as a metallurgical engineer (or at least that is what my degree says.... not really what I do for work anymore) almost all metals in the earth are in the form of metal oxides. Alum oxide is very difficult to break the bond, recycling and remelting takes approx 10% of the energy of making new alum metal from the alum oxide. This is why most all alum production facilities are located by low-cost hydro-electric power sources. The reduction of the alum oxide is very electric power intensive. There is not any lower cost or easier chemical reduction process.

In comparison, new iron (steel) from iron oxide is approx the same cost as remelting scrap. Of course recycled scrap is better environmentally, but from cost standpoint it does not have as much incentive compared with aluminum.