scan0016 3

l:quid-liquid extraction IN hydrometallurgy 3

This i s why it isessential in the early stages of development of a liquid-Iiquid extraction circuit that the actual leach liquor is used, rather than a simulated leach liąuor madę to match the analytical data or, worse still, pure laborat-ory Solutions containing just the major elements.

1.2 Liquid-liquid equilibria [See also Newsham, Vol. 1]

The basie solvent extraction circuit in hydrometallurgy consists of a series of interconnecting loops (Fig. 1.2) that allows the desired element to be trans-ferred first into an immiscible organie phase, which may then be contacted with a series of aqueous Solutions designed to strip, or back extract, any impurities coextracted with the desired element. This process is termed scrubbing, and the resulting aqueous scrub raffinates may then be further treated to remove any valuable elements. Finally the purified organie phase is contacted with an appropriate strip solution to return the chosen element to an aqueous phase from which it can be recovered, thereby regenerating the organie extractant solution for recycling. The ability to recycle a number of these process streams is a desirable feature of the flowsheet. Inevitably

Ore

Depletcd

leachate

Stripped

organie

Depleted

aqueous

Impurities

Metal

Fig. 1.2. Typical solvent extraction How sheet for the rccovery of metals from a leach solution.