THE USE OF ION-EXCHANGE RESINS FOR THE RECOVERY OF VALUABLE SPECIES FROM SLURRIES OF SPARINGLY SOLUBLE SOLIDS

An example of an industrial process which recovers valuable species by shifting the solid/liquid dissociation equilibrium condition is the e xtraction of rare earths from low-grade kaolinite ore by percolation l eaching. Valuable species can be recovered from such sparingly soluble solids which slightly dissociate to give traces of the valuable ions in solution, using ion-exchange resins in a slurry mixture. A dissocia tion equilibrium exists between the dissolved ions in solution and the solid ore. If the dissolved ions are removed from solution by ion-exc hange, thus continually displacing the solid/liquid dissociation equil ibrium condition, further dissolution of the solid is required accordi ng to Le Chatelier's principle so as to restore the equilibrium concen tration of the valuable species in solution. It is possible to recover valuable metals from sparingly soluble solids, such as metal sulphate s, by contacting a slurry of the solid with an ion-exchange resin. As a result of the ion-exchange that takes place, electrolyte solutions a re created which facilitate the dissolution process and hence the over all extraction process by changing the activities of the species in so lution. Complete dissolution of the solid, hence complete liberation o f the valuable metal species, can be achieved provided that a sufficie nt amount of ion-exchanger is used. The extraction of base metal sulph ates was used as a case study.