The mineral resources of the industrialized countries, especially the
member nations of the North Atlantic Treaty Organiza- tion, are being
depleted at such a rate that more and more of these count ries are
beginning to depend on ore imported from other coun- tries. To sustain
the economic and strategie well-being of these member countries, it
becomes imperative that a program of developing and exploiting other
non-conventional mineral resources and a con- servation program where
metal values from waste dumps and scrap metals and alloys are recycled
must be initiated and implemented. In order to meet this challenge, new
processes and technology must be available for consideration in the
design and operation of the new plants. One of the possible routes of
extracting the metals from their ores, especially for multimetal complex
ores and very low grade ores, is by hydrometallurgical processing. The
hydrometallurgical route of metal recovery where dissolution (leaching),
separation and concentration (ion exchange, solvent extraction, and
membrane separation) and reduction to metal (cementation, precipitation
by gaseous reduction, and electrolysis) is carried out at near ambient
temperature is becoming more competi- tive with the conventional high
temperature processes used in the smelting of metals from high grade and
beneficiated ores.