Answer: Hydrometallurgy (bioleaching or acid leaching + solvent extraction + electrowinning).
- A Hydrometallurgy (bioleaching or acid leaching + solvent extraction + electrowinning)
- B A blast furnace process identical to that used for iron extraction in most textbook accounts
- C The Hall-Heroult electrolytic process used instead for aluminium during normal conditions
- D The thermite reaction used instead for welding iron rails as generally observed
Correct answer: A. Hydrometallurgy (bioleaching or acid leaching + solvent extraction + electrowinning)
Explanation: Low-grade Cu ores are heap-leached with dilute H<sub>2</sub>SO<sub>4</sub> (bacterial oxidation helps); Cu<sup>2+</sup> in solution is extracted and electrowon as pure Cu.
An Ellingham diagram plots ΔG° of oxide formation against temperature for different metals; whichever line is LOWER (more negative ΔG°) at a given temperature reduces the oxide of any metal whose line sits above it - the basis of carbon reduction (Fe, Zn) vs electrolytic reduction (Al, Mg, Na) decisions.
Concept context
The science of extracting metals from ores and refining them for use. Covers concentration methods, reduction techniques, refining processes, and the thermodynamic principles that govern metal extraction.