Historical Development

Table 1 Key stages in flotation process development

Year

Concept introduced

Inventors

1860

Oil as a carrier

Haynes

1901

Gas as buoyant medium

Potter/Froment

1902

Ultraflotation/carrier flotation

Cattermole

1905

First generation flotation

machines

Hoover

1908

Frother (organic compounds)

Higgins/Sulman etal.

1912

Activator (CuSO4 for sphalerite)

Bradford

1913

Depressants (SO2 for activated

sphalerite)

Bradford

1925

Modern flotation collectors

(xanthate for sulfides)

Keller

development of the flotation process in the various key stages. Nevertheless, Table 1 provides a general picture of how flotation has evolved since its first applications in mineral processing.

As shown in this table, up until the 1930s all the ingredients required for selective flotation had been proposed, including: (i) a collector to render target particles water-repellent by its adsorption; (ii) a frother to stabilize bubbles and promote foaming; (iii) an activator to induce or enhance collector adsorption on target particles; and (iv) a depressant to destroy collector adsorption on unwanted particles; along with bubble generation in a flotation machine.

Process dynamics

FlotationYvstem Physical

Chemical Mechanical

Figure 1 A flotation system shown as a tetrahedron with chemical, mechanical and physical aspects as the foundation through which process dynamics is modelled and controlled. The triangular base plane emphasizes the interrelated nature between the three foundation elements. The chemical aspect involves control of chemistry at air- and solid-aqueous interfaces by collectors, depressants, dispersants, activators, bacteria and frothers; the mechanical aspect concerns energy dissipation for bubble generation, particle dispersion, surface cleaning, hydrodynamic forces and bubble-particle contact; the physical aspect deals with the wetting phenomena and the nature of interactions between bubble-particle, bubble-bubble and particle-particle pairs in aqueous solutions involved in a flotation system.

These ingredients form one of the three foundations on which a flotation system is built. This is shown in Figure 1 as flotation chemistry. Although neither the principles involved in flotation nor these basic ingredients have been changed since, the technology along with the fundamental understanding of the processes have evolved greatly. Developments in each of these three foundations are summarized in this article with emphasis on recent advances.

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