Flotation Processing

Grinding of base metal ores is done in water to which certain oils and synthetic chemicals are added. Then the resulting pulp is swirled around in rectangular tanks arranged in series. These tanks are known as flotation cells. Controlled air and further chemicals, called flotation reagents, are added. The air forms bubbles in the pulp, the flotation reagents coat the metal sulphides (but not the waste particles) and cause them to stick to the bubbles which, in turn, carry the sulphides to the top of the tanks.

The sulphide-carrying bubbles are scraped from the top of the flotation machines, while the worthless material left behind sinks to the bottom and is discharged.

A recent innovation, designed to improve flotation recoveries, has been to use column flotation cells — 10-meter-tall (33 feet) tanks in which a tall column of froth can develop. Water sprayers at the top wash unwanted minerals from the froth, so that only minerals that are chemically attracted to the bubbles are retained.