extractionelectrowinning

Extraction electrowinning, typically referred to as SX-EW, is a hydrometallurgical process that combines solvent extraction and electrowinning to recover metals from aqueous solutions produced by leaching. It is most widely used for copper production and has also been applied to certain nickel, cobalt, and zinc operations.

In a standard SX-EW flow sheet, the ore is leached with acid (commonly sulfuric acid) to generate a pregnant leach solution containing dissolved metal ions. The copper is transferred from the aqueous phase to an organic solvent in a solvent-extraction step using a suitable extractant. The loaded organic phase is then stripped with acid to produce a copper-rich electrolyte. This electrolyte is directed to electrowinning cells, where copper metal is plated onto cathodes while the solution is recycled to sustain the process.

Advantages of SX-EW include lower capital and energy costs compared with traditional smelting, the ability to process low-grade or oxide ores, and the production of high-purity copper with reduced air emissions. The process is also adaptable to heap or in-situ leaching in favorable deposits and allows selective metal recovery through solvent choice.

Limitations involve its narrow applicability to certain metals, with copper being dominant; complexity in solvent management and phase stability; sensitivity to impurities; and higher operating and maintenance requirements for solvent extraction systems. Environmental controls focus on managing acids, organics, and spent scrubbers, as well as safeguarding electrical equipment in electrowinning cells.