Industrial mixer settlers are commonly used in the copper, nickel, uranium, lanthanide, and cobalt hydrometallurgy industries, when solvent extraction processes are applied.
They are also used in the Nuclear reprocessing field  to separate and purify primarily Uranium and Plutonium, removing the fission product impurities.
In the multiple countercurrent process, multiple mixer settlers are installed with mixing and settling chambers located at alternating ends for each stage (since the outlet of the settling sections feed the inlets of the adjacent stage's mixing sections). Mixer-settlers are used when a process requires longer residence times and when the solutions are easily separated by gravity. They require a large facility footprint, but do not require much headspace, and need limited remote maintenance capability for occasional replacement of mixing motors. (Colven, 1956; Davidson, 1957)
The equipment units can be arrayed as:
*extraction (moving an ion of interest from an aqueous phase to an organic phase), 
*washing (rinsing entrained aqueous contaminant out of an organic phase containing the ion of interest), and 
*stripping (moving an ion of interest from an organic phase into an aqueous phase).