Solvent extraction (SX) is an established industrial separation technology in non-ferrous and battery metals refining and recycling, REE separation and purified phosphoric acid production.

Across copper, nickel and cobalt refining, uranium recovery and purification, REE separation and purification, and black mass processing, SX is used because it can deliver highly selective separations at industrial capacity and produce high purity strip for downstream electrowinning or crystallization, depending on the process and product specification (i.e. a REE oxalate or plated cobalt).

In a typical hydrometallurgical flowsheet, after upstream leaching, the pregnant leach solution (PLS) enters the solvent extraction process to selectively transfer one or more target metals into the organic phase. Depending on the chemistry, concentration levels, impurity profile, and project economics, SX may be complemented by precipitation and/or ion exchange, but this technology still remains the key element of the value chain.

For many years, mixer-settlers were the de facto standard for many solvent-extraction duties because of their operating simplicity, established industrial history, and ability to accommodate very high flowrates. Column-based solvent extraction technology has also existed for decades and has been used primarily in the recovery of organic chemicals, but interest in it is increasing in areas such as REE processing, purified phosphoric acid production, waste and side stream valorisation and wastewater scavenging.