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GCSE Chemistry · key term
A biological extraction method in which plants absorb metal ions from soil through their roots and concentrate them in their tissues.
Used by Edexcel and OCR
Specification 4.8 · Paper 1
Revise: Biological Extraction MethodsThe two methods required here are phytoextraction, which uses plants, and bacterial extraction, commonly called bioleaching. They can make low-grade ores, mine waste or contaminated soils useful, but both are generally slow. They are therefore alternatives for suitable circumstances, not automatic replacements for every conventional method.
Specification C6.1c · Paper 2 (Foundation), Paper 4 (Higher)
Do not confuse the two routes: phytoextraction uses plants and produces metal-rich ash; bioleaching uses bacteria and produces a leachate containing metal ions.
Avoid claiming that biological extraction has no environmental impact. Phytoextraction involves land use and burning harvested plants, while poorly managed bioleaching can release acidic or toxic substances.
Keep the methods distinct: plants absorb metal ions in phytoextraction; bacteria help release metal compounds into a leachate in bacterial extraction.
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Extraction of metal compounds using plants that absorb them through their roots.
In phytoextraction, also called phytomining, plants grow in soil containing copper compounds and absorb them through their roots. The plants are harvested and burnt, leaving ash containing copper compounds. Mixing the ash with water produces a solution from which copper can be obtained by displacement or electrolysis.
Paper 1 (Foundation), Paper 2 (Foundation), Paper 3 (Higher), Paper 4 (Higher)
The use of plants to absorb metal ions from soil so that metal compounds can be recovered from the harvested plants.
Revise: Biological metal extractionOCR focuses on two alternatives for extracting relatively unreactive metals: bacterial extraction and phytoextraction. These methods can also recover metals from waste material rather than requiring newly mined ore.