Flotation cells are machines that can be used to separate graphite from black mass through a hydrophobicity-based process. In battery recycling, flotation is a key technique for isolating graphite after mechanical pre-treatment. The process works by suspending the black mass in water and adding chemical reagents—collectors and frothers—that promote the attachment of hydrophobic graphite particles to air bubbles. As air is bubbled through the slurry in the flotation cell, graphite rises to the surface in a foam layer, which is then skimmed off for collection.

Mechanical flotation cells consist of a tank with a stirring system, air supply, froth skimmer, and discharge unit. The stirring system ensures proper mixing of reagents and uniform bubble distribution, while the froth skimmer collects the graphite-rich foam. This method is widely used for its efficiency in separating valuable materials from complex mixtures.