Copper extraction from sulfate leach liquors

Amine salts represent the only commercially important class of extractants of the anion-exchange type. Their most widespread use is in the extraction of uranium from sulfate leach liquors, but they have found application in the recovery of cobalt, zinc and copper from chloride solutions, as well as in the extraction of metals that readily form oxyanions, such as vanadium, molybdenum and tungsten. 

It will be instructive to consider briefly the methodology employed in the development of solvent extraction processes that have become operational. The development of the Bluebird Mine operation for the extraction of copper from dump leaching liquors by solvent extraction and the subsequent recovery of copper as either copper sulfate or cathode copper is used as an example. The initial investigations [11] included the following ... 

Copper and nickel are subsequently removed from the leach liquor by solvent extraction. After selective stripping, nickel sulfate is produced by crystallization and copper metal by electrowinning. 

The copper-specific extractants used to extract copper from other base metals in acidic sulfate liquors are known as hydroxyoximes, and the interaction is known as chelation. The basic structures of modem oxime extractants are shown in Figure 5.4, where A = H for aldoximes and A = CHj for ketoximes. The R-chain is usually C9H19 (occasionally C12H25). The complexation of copper by these extractants is shown schematically in Equation (5.1). Extraction of each copper ion releases two protons, thereby providing a useful source of acid for further leaching (see Figure 5.2). pH is an important parameter controlling the equilibrium position of this reaction. 

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