ABSTRACT
The effective separation of valuable minerals from gangue by flotation is realized by making the surface of the desired mineral more hydrophobic, while maintaining the surface of valueless minerals hydrophilic. This chapter reviews activation phenomena of inorganic compounds on oxides, salt-type minerals, and sulphides. The term activator should be used specifying clearly the kind of surface and collector. In other words, an activator for one mineral can be a depressant for another with a different collector. The surfaces of minerals are subject to modification by the adsorption of polyvalent ions and their hydrolyzed complexes. The adsorption of these ions frequently originates by the difference in charge between the ions and the surface. Sodium silicate is one of the most widely used depressants in flotation practice. However, it has been reported that small additions of sodium silicate activate some minerals. Sulfide ion is a well-known activator for oxidized sulfides and metals when they are subjected to flotation with thiol collectors.
