Chapter 17 - Extractive Metallurgy
Review articleOpen access
1997/01/01 Simple chapter DOI: 10.1016/B978-012678550-0/50017-2
Publisher SummaryThis chapter discusses several methods for the extraction of metals from minerals. The simplest concentration technique is the use of gravity to separate dense metal or ore particles from the much less dense silicate and other rock-forming minerals by suspending the latter, finely divided in swirling water. Froth flotation is another method that is widely used to concentrate ores, particularly sulfides such as galena (PbS), although it is by no means restricted in use to metallic sulfides. In the case of metal sulfides, the crushed rock is suspended in water, and the particles of metal sulfide, which may be denser than the unwanted siliceous gangue, are nevertheless caught up in a froth generated by blowing air through the mixture after addition of a frothing agent, such as pine oil. The froth can then be skimmed off the top and the metal sulfide recovered. Hydrometallurgical methods use reactions in aqueous solution to concentrate and/or separate the metal ions of interest, such as the heap leaching of low-grade copper ores with acid. Difficult separations can often be effected by liquid–liquid solvent extraction, which depends on differences in the distribution of solute species between two immiscible or partially immiscible phases.
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