ABSTRACT
A special class of purification treatments is necessary to separate chemically similar metals or to free them from the impurities. As a unit operation for solution purification and upgrading, it came into prominence after its large-scale applications in the treatment of cyanide solutions of gold and silver were realized. It is in these specific applications that the three processes, namely ion exchange, carbon adsorption, and solvent extraction (SX), are admirably suitable. The chapter presents a preliminary outline of the SX process in general. The liquid cation exchange, based on the SX process as the name suggests, operates through the exchange of cations between the aqueous and organic phases. The liquid anion exchangers function by ion exchange mechanism analogous to that observed in the resinous anion exchangers. Neutral extractants include a number of neutral solvating agents which facilitate extraction by coordinating with the metal with simultaneous displacement of water molecules and formation of a neutral complex through ion association.
