Enrichment of Platinum Group Metals (PGMs) by two-stage selective pressure leaching cementation from low-grade Pt-Pd sulfide concentrates

A hydrometallurgical process was developed for producing Pt-Pd enriched concentrates from low-grade sulfide concentrates on-site at Jinbaoshan mine in an isolated area in China. The developed process (pressure acidic leaching-pressure cyanidation leaching) includes the following two steps. (1) The flotation concentrates are treated by acidic pressure leaching to selectively dissolve all the base metals (Cu, Ni, Co) while leaving most (85 to 94 pct) of the precious metals in the iron residues. The leaching solution is then processed by copper cementation and solvent extraction (SX) to recover PGMs and CuNiCo, respectively. (2) The iron residues are treated by pressure cyanidation leaching to selectively dissolve precious metals. The cyanidation solution is then cemented by zinc power reduction to produce Pt-Pd concentrates. Testing results from both lab and pilot (5 kg/batch, 50 L autoclave) scale tests show that Pt + Pd content has been increased from 86 g/t (flotation concentrate) to 56 to 59 wt pct (zinc cementation residue) with an extraction recovery of 95.8 pct. The Pt-Pd enriched cementation residues can be sold as Platinum Group Metal (PGM) concentrates to refineries for further refining.