Britannica Sources used in this answer

How does solvent extraction purify copper leach solutions?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

A periodic table element box for copper shows its symbol Cu, atomic number 29, atomic weight 63.546, electron configuration, and name. Icons indicate copper is a solid, weakly basic transition metal with face-centered cubic crystal structure. A key explains the symbols and color coding. — copper Properties of copper.

Solvent extraction is a critical process in hydrometallurgy used to purify and concentrate copper from dilute leach solutions, making them suitable for electrowinning.12

The process functions through the following steps:

Extraction: A large volume of dilute copper leach solution is mixed with a smaller volume of a water-immiscible organic solvent, typically dissolved in kerosene. The copper ions transfer from the aqueous leach solution into the organic solvent.2
Phase Separation: The two liquids are separated, effectively isolating the copper from impurities like iron that remain in the original leach solution.12
Stripping: The copper-loaded organic solvent is contacted with a different fluid that has a higher affinity for the metal. This fluid strips the copper from the solvent, resulting in a small, highly concentrated volume of copper solution.2

By increasing the concentration—for example, from 2.5 grams per litre to 50 grams per litre—this method allows for the efficient recovery of copper from low-grade ores that would otherwise be difficult to process economically.12