Bioleaching and phytomining sim
Grow plants on low-grade ore, burn them and dissolve the ash, or let bacteria leach a column of ore week by week, then get the copper out with scrap iron or electrolysis and weigh it.
Metals: extracting copper from low-grade ores · covers the GCSE (Higher) topic
What the sim shows
Copper-rich ores are running out. Low-grade ores hold too little copper to be worth digging up, crushing and smelting in the usual way, so biological methods are used instead: bioleaching is already used by mining companies, while phytomining is still being tested. Both avoid digging, moving and dumping huge amounts of rock. Phytomining: plants grown on the ore absorb copper compounds; they are harvested and burned, and the ash, far richer in copper than the ore, is dissolved in dilute sulfuric acid. Bioleaching: bacteria living on the ore produce a leachate solution that contains copper compounds. Copper metal is then got from either solution by displacement with scrap iron (Fe + CuSO₄ → FeSO₄ + Cu; iron is more reactive than copper) or by electrolysis (copper forms on the negative electrode: Cu²⁺ + 2e⁻ → Cu). Weighing them up. Good points: they use low-grade ore and old mine waste that would otherwise be thrown away, need less energy than digging and smelting, leave less rock to dump and give off less sulfur dioxide. Bad points: both are slow (plants take a season to grow; real bioleaching heaps take months to years) and give only small amounts of copper; phytomining needs a lot of land; bioleaching makes an acidic, toxic leachate that must not leak into the ground. All the numbers here are illustrative, because real ore grades, plant uptakes and leaching rates vary widely: ore 0.50 % copper; a 1.00 kg column leaches up to 70 % of its copper, 70 % × (1 − e^(−weeks ÷ 6)), into 1.00 dm³ of leachate; each season the plants (50.0 g dry, burning to 5.00 g of ash) take 5 % of the copper left in 2.00 kg of ore soil. That uptake (1 % of the dry plant) is exaggerated about ten times, so there is enough copper to weigh: the best copper-collecting plants reach about 0.1 %. Aᵣ: Cu 63.5, Fe 56. Recovery takes out all the dissolved copper (idealised).
- Evaporating basin: the plants burn to ash that is rich in copper compounds
- Column of crushed low-grade ore: bacteria leach the copper into the beaker below
- Scrap iron or carbon electrodes: get the copper metal out of either solution
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