Froth Flotation

Froth flotation is a mineral-processing technique for separating valuable minerals from the surrounding waste rock, or gangue, by grinding the ore into a fine slurry, adding chemical reagents that make the target mineral's particles water-repellent, and then bubbling air through the mixture so those particles cling to the rising bubbles and are carried up into a froth that can be skimmed off the surface, while the wettable gangue particles remain in the pulp below. Various inventors in Britain, Australia and the United States patented competing froth flotation processes in the years around 1900, most notably the Elmore brothers in 1898 and the team of Henry Livingstone Sulman, Hugh Fitzalan Kirkpatrick Picard and John Ballot in 1906, and the method quickly proved able to economically process low-grade sulfide ores that older gravity-separation methods could not touch. Froth flotation remains the dominant method of concentrating copper, lead, zinc and many other base-metal ores worldwide, and its success in extending the economic life of low-grade ore deposits is often credited with keeping metal mining viable through the twentieth century.