Phytomining & BioleachingOxford AQA IGCSE Chemistry: Revision notes

Traditional mining of high-grade metal ores is becoming less sustainable as supplies of these ores are running out. Two newer methods — phytomining and bioleaching — are being researched and used to extract metals, particularly copper, from low-grade ores that would not be worth mining by traditional methods.

Phytomining uses plants to absorb metal compounds from the ground. The process works like this:

1. Plants are grown on land containing low-grade metal ore
2. As they grow, the plants absorb metal compounds from the soil through their roots
3. The plants are harvested and then burned
4. The ash produced contains the metal compounds, which can be processed further to extract the metal

Bioleaching uses bacteria to extract metal compounds from ores. The bacteria feed on the ore and produce a solution, called a leachate, that contains dissolved metal compounds. This leachate can then be processed (e.g. by electrolysis or displacement with scrap iron) to obtain the pure metal.

Phytomining and bioleaching are being researched and developed mainly to reduce the environmental impact of traditional mining. Traditional mining involves digging up large amounts of rock, which:

• Damages landscapes and habitats
• Produces large amounts of waste rock
• Requires a lot of energy

Because phytomining and bioleaching can work with low-grade copper ores (which would otherwise not be worth extracting), they allow metal to be recovered without needing to mine new, higher-grade deposits, extending the availability of a limited resource while reducing environmental damage.