MODIFICATION AND PREPARATION OF POLYMERIC ADSORBENTS FOR PRECIOUS-METAL EXTRACTION IN HYDROMETALLURGICAL PROCESSES

This paper describes the efforts made to develop polymeric adsorbents that could be applied to the recovery of precious metals (Au, Pt, Pd a nd Rh) from cyanide leaching solutions. The polymeric adsorbents prepa red should fit the following criteria: be compatible with the nature o f the leaching solutions concerned; have good selectivity patterns aga inst the other metal cyanides; have good elution properties and be com patible on integrated systems of leaching and extraction (resin-in-pul p (RIP) and resin-in-leach (RIL)). Knowledge of the chemical speciatio n of the target metals in the leaching solutions to be treated and the nature and structure of the metal complex to be extracted is very imp ortant in understanding the metal-extraction reactions and selectivity factors. As selectivity patterns are greatly influenced by the polyme r structure, ionic density and hydrophilic/hydrophobic nature of the p olymeric supports, the definition of the structure and functionality o f the polymeric supports has been based on the chemical speciation as one of the more effective options for polymer support selection. Two m ethods have been used in selecting polymeric adsorbents: commercial io n-exchange resins and ion-exchange impregnated resins prepared by phys ical immobilisation of selective and specific reagents used in solvent extraction onto high surface polymeric materials. Both types of mater ial were evaluated in two applications: extraction and recovery of gol d cyanide from leaching liquors and recovery of Pt, Pd and Ph from lea ching solutions obtained on cyanidation steps of automobile catalytic converters. The introduction of both polymeric materials is directed t owards the selective recovery of gold and precious metals (Pt, Pd, Ph) as an alternative to defined processes based on adsorption steps by a ctivated carbon and/or precipitation by thermal processes. (C) 1998 El sevier Science B.V. All rights reserved.