Overview
This lecture covers methods of extracting metals, particularly copper, from high and low grade ores, focusing on phytoextraction, bioleaching, and reduction techniques.
Ore Types and Scarcity
- An ore is a rock that contains enough of a metal compound to make extraction worthwhile.
- High grade ores have a high concentration of metal compounds; low grade ores have less.
- High grade copper ores are becoming scarce, so extraction from low grade ores is necessary.
Phytomining
- Phytomining extracts metal compounds from soil using plants.
- Plants grow on soil with metal compounds (e.g., copper oxide) and absorb them.
- Burning these plants leaves ash rich in metal compounds for further extraction.
Bioleaching
- Bioleaching uses bacteria to extract metal compounds from rocks.
- Bacteria produce a liquid called leachate that contains dissolved metal compounds.
- The leachate is collected for metal extraction.
Extracting Pure Metals
- If a metal is less reactive than carbon (like copper), it can be extracted by reduction with carbon.
- Scrap iron can displace metals less reactive than iron from their compounds.
- Metals more reactive than carbon (e.g., aluminium) require extraction by electrolysis, which is expensive.
Practice Questions Recap
- Phytomining uses plants to absorb and concentrate metals, with extraction occurring after burning.
- Bioleaching uses bacteria to produce leachate rich in metal compounds.
- Reduction with carbon or scrap iron works only if the target metal is less reactive than carbon or iron, respectively.
Key Terms & Definitions
- Ore — rock containing enough metal compound for profitable extraction.
- High Grade Ore — ore with a high percentage of metal compounds.
- Low Grade Ore — ore with a low percentage of metal compounds.
- Phytomining — extracting metals from soil using metal-accumulating plants.
- Bioleaching — process using bacteria to obtain metal compounds, producing leachate.
- Leachate — liquid produced by bacteria during bioleaching, containing dissolved metals.
- Reduction — extraction method where a less reactive metal is displaced from its compound by carbon.
- Electrolysis — method using electricity to extract metals from compounds.
Action Items / Next Steps
- Complete the provided practice questions on extraction methods.
- Review definitions and differences between phytomining and bioleaching.