Ore to Metal: Froth Flotation and the Aluminium Cell

Also called

froth flotation · concentration of ore · sulphide ore · pine oil collector · froth stabiliser · gangue · galena · zinc blende · Hall-Heroult process · electrolytic reduction · extraction of aluminium · alumina · cryolite · carbon anode · metallurgy · झाग प्लवन विधि · अयस्क · ऐलुमिनियम का निष्कर्षण

Topics

• Froth flotation concentrates sulphide ores such as galena (PbS) and zinc blende (ZnS) by removing gangue.
• Crushed ore is stirred with water; pine oil (the collector) wets the sulphide grains, water wets the gangue.
• Air blown through the pulp makes froth; oil-coated sulphide grains cling to the bubbles and rise into it.
• The froth is skimmed off and dried as concentrate; the gangue sinks and is drained away.
• In the Hall–Héroult process purified alumina (Al₂O₃) is dissolved in molten cryolite (Na₃AlF₆) with CaF₂.
• Cryolite lowers the melting point from about 2320 K for pure alumina to about 1220 K and makes the melt conduct.
• The carbon-lined steel tank is the cathode: Al³⁺ + 3e⁻ → Al; the molten aluminium sinks and is tapped off.
• At the carbon anodes oxide ions give up electrons and the oxygen burns the carbon: C + 2O²⁻ → CO₂ + 4e⁻.
• Overall 2Al₂O₃ + 3C → 4Al + 3CO₂: the anodes burn away and must be lowered and replaced.

About this model

A GLB file of about 759 KB, shown in Lably's 3D viewer and, on a phone, placed in your room with AR. Credit: Model, science and animation: Lably (built procedurally with three.js; no downloaded meshes). | CC BY 4.0. Original geometry and animation made for Lably.

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