Two steps:
The ore
Bauxite (Country Les Baux en Provence) is a red-brown ore composed of aluminum oxide .. 1 .., iron oxide (III) .. 2 .. and sand (silicon oxide) .. 3 .. The extraction of aluminum oxide The dried and pulverized bauxite is processed (Bayer process) with a concentrated solution of sodium hydroxide under elevated pressure and temperature. The only soluble product, sodium tétrahydroxoaluminate $Na^++ Al(OH)_4^- $ is then filtered. From this solution the aluminum hydroxide is precipitated by the action of carbonic acid: .. 4 .. The latter substance is isolated by filtration and then converted into aluminum oxide by pyrolysis at $1100^o C$: .. 5 .. The electrolytic bath Aluminum oxide has a melting temperature of $2045^oC$. To lower the melting temperature, it is mixed with cryolite $((Na^+)_3 (AlF_6^{3 -})) $ (sodium hexafluoroaluminate) manufactured by the action of sodium hydroxide on hydrofluoric acid and aluminum oxide:
1)$Al_2O_3$ 2)$Fe_2O_3$ 3)$SiO_2$ 4)$Al(OH)_4^-+H_2CO_3$ $\rightarrow$ $ Al(OH)_3+H_2O+HCO_3^-$ 5)$2Al(OH)_3$ $\rightarrow$ $Al_2O_3+3H_2O$
1. Cathode connection 2.3. Graphite cathode 4. Electrolyte 5. Anodes connection 6. Anodes 7. The electrolytic bath 8. Melted aluminum 9.11. Iron tray 10. Graphite plug 12. Insulation layer
Electrolysis is conducted at $950^oC$ at a voltage of $5 \;V$ and a current intensity of $200.000 \; A $. In the electrolytic bath there swim between other unbound aluminum ions $Al^{3+}$ that will be reduced as well as unbound oxide ions $ O^{2 -}$ that will be oxidized into oxygen atoms by reacting with the graphite carbon producing an equimolar mixture of carbon monoxide and carbon dioxide: Cathode: .. 6 Anode: .. 7 Reaction with carbon: .. 8 To produce $ 1\;t $ of aluminum, we need $1.9 \; t$ of aluminum oxide, $ 0.5 \; t $ of graphite, $ 50 \; kg$ cryolite and $ 15,000 \; kWh$ electricity, enough energy to heat a single family home for 5 years, hence the importance of aluminum recycling!
6)$Al^{3+}+3e^-$ $\rightarrow$ $Al$ 7)$O^{2-}-2e^-$ $\rightarrow$ $O$ 8)$3O+2C$ $\rightarrow$ $CO_2+CO$