The use of ion-exchange resins for the recovery of valuable species from slurries of sparingly soluble solids

[摘要] ENGLISH ABSTRACT:The availability of vast deposits of high-grade ore bodies are rapidly becomingsomething of the past in the modern mining and metallurgical scenario. Apart from thelower grade content of these ore bodies, complex mineralogy are an even greaterobstacle in the recovery of valuable metal species. The development of new technology todeal with these type of ore bodies is therefore critical and worth investigating, as theworld's easily exploitable high grade ore deposits are decreasing.Valuable species can be recovered from sparingly soluble solids, which slightlydissociate to give traces of the valuable ions in solution, with the use of ion-exchangeresins in a slurry mixture. A dissociation equilibrium exists between the dissolved ions insolution and the solid ore body. Jf the dissolved ions are removed from the solution byion-exchange, the solid / liquid dissociation equilibrium is continually displaced.According to Le Chatelier's principle further dissolution of the sparingly soluble solid isrequired to restore the equilibrium concentration of the valuable species in solution.It is possible to recover valuable metal species from metal precipitates, such as metalsulphides, by contacting a slurry of the precipitate with a suitable ion-exchange resin.The resulting ion exchange reaction between the valuable metal species and counter ionscreates electrolyte solutions that may facilitate the further dissolution of the metalprecipitate. These counter ion electrolyte solutions may easily become significantlyconcentrated. This occurs in the event of a Resin-in-Leach (RIL) mixture that results in acontinuous ion-exchange reaction taking place due to the continually changingelectrolyte composition of the mixture, which significantly changes the activities andhence the solubility of the valuable metal species in solution. Complete dissolution andliberation of the metal precipitate can often be achieved provided that a sufficient amountof a suitable high capacity ion-exchange resin is used in a properly engineered Resin-in-Leach (RIL) circuit.The simultaneous dissolution and adsorption of various base metal precipitates weretested. Various interactions that take place in the slurry at molecular level as well as theeffects of various variables on the adsorption by dissolution process are discussedthrough the development of fundamental thermodynamic models. These thermodynamicmathematical models are developed for the three phase system that exists in a Resin-in-Leach mixture, i.e. the solid ore body, the electrolyte solution and the ion-exchange resin,and can be used for possible other applications such as the recovery of rare earths fromlow grade ores in the minerals processing industry. A typical example of an industrialprocess for the recovery of rare earth species is the percolation leaching of rare earthsfrom low-grade kaolinitic ores, which continually shifts the solid / liquid dissociationequilibrium condition. The rare earth content of these ores is usually between 0.05%and0.3 %, which is very low by any modern industrial extraction and refining standards.

[发布机构] Stellenbosch University