Flotation chemistry and technology of nonsulfide minerals

The dimensions of nonsulfide flotation technology extend in many directions, as might be expected from the diversity of the mineral classes, which include soluble salt minerals (potash, borax, and trona), semisoluble salt minerals (phosphate minerals, fluorite, calcite, and barite), and insoluble oxides/silicate minerals (iron oxide minerals, rutile, mica, quartz, and feldspar). Consequently, some flotation separations are accomplished from saturated brine, though other separations are achieved in solutions of rather low ionic strength. Also, certain nonsulfide minerals are naturally hydrophobic, such as talc, graphite, and coal. However, in general, the nonsulfide minerals are hydrophilic and require relatively high levels of collector addition on the order of 1 lb/ton to establish a hydrophobic surface state. In addition, the nonsulfide collectors generally are anionic or cationic surfactants, having hydrocarbon chains of 10 carbon atoms or greater. In many instances, the collector is sufficiently insoluble so that a distinct collector phase is present in the system, existing as a liquid dispersion or as a collector colloid. This situation further complicates the analysis of nonsulfide flotation chemistry. Thus, in some cases, the hydrophobic surface state is created by the adsorption of water-soluble collector species, though in others, the hydrophobic surface state is created by the wetting/spreading of insoluble collector oils or by the attachment of insoluble collector colloids. In view of the foregoing, it is evident that the flotation chemistry of nonsulfide minerals is distinctly different from the flotation chemistry/electrochemistry of sulfide minerals.