Answer: Oxidation of Fe2+ to Fe3+ (which then oxidises sulfide mineral) and oxidation of CuS/Cu2S to CuSO4.
- A Oxidation of Fe2+ to Fe3+ (which then oxidises sulfide mineral) and oxidation of CuS/Cu2S to CuSO4
- B The direct reduction of the dissolved Cu2+ ions all the way down to metallic elemental copper
- C The straightforward dissolution of the silica gangue minerals scattered within the ore body
- D The complete neutralisation of the acidic bioleaching solution back to a roughly neutral pH
Correct answer: A. Oxidation of Fe2+ to Fe3+ (which then oxidises sulfide mineral) and oxidation of CuS/Cu2S to CuSO4
Explanation: Bacteria regenerate Fe3+ which is the actual oxidant: Cu2S + 2Fe3+ → 2Cu2+ + 2Fe2+ + S; bacteria then reoxidise Fe2+ → Fe3+ completing the cycle.
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.