A conceptual hybrid process flowsheet for platinum group metals (PGMs) recovery from a chromite-rich Cu-Ni PGM bearing ore in oxidized mineralization through a single-stage leach and adsorption onto ion exchange resin

Abstract

The availability of oxidized PGM ore deposits, at or near the earth's surface, present lucrative prospects for future PGM production owing to the large resource estimates, the relatively high PGM grades and they can be mined through relatively lower-cost open-pit mining processes. However, these oxidized PGM ores are currently not mined or treated due to insufficient recoveries using established metallurgical techniques. The complex mineralogy and polymodal distribution of PGM in the oxidized ores pose a number of challenges to the metallurgist from a mineral liberation and extraction perspective. A conceptual route to the integrated processing of a Ni-Cu-PGM bearing chromite ore in oxidized mineralization for the recovery of base and precious metals is presented based upon earlier work of the authors and recent research on metal recovery from solution. This paper presents laboratory batch-scale results of simultaneous adsorption of Pd(II) and Pt(IV) onto commercially available weak-base anion exchange resin, diethylaminoethyl (DEAE) cellulose, from hydrochloric acid solutions. Effects of various variables such as equilibration time, thiocyanate and tin chloride concentrations were studied. Without any prior scrubbing step to remove co-extracted impurities, the uptake of Pd(II) and Pt(IV) was successfully accomplished with recoveries approximating 100% within 15 min. The presence of Fe(III) and other non-ferrous metal accompanying ions didn't show any marked tendency to adsorb. Among the adsorption parameters, thiocyanate concentration had the most significant effect on the process. The dual role of Sn(II) i.e. labilizing agent and PGM collector at a time, was simply overridden, overshadowed by the DEAE high selectivity for PGMs. Thiourea proved to be a better stripping reagent for bulk elution of combined Pd(II) and Pt(IV). A conceptual flowsheet is disclosed for hydrometallurgical pilot scale testing, economic evaluation and assessment of potential environmental impacts.