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 1 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.

The chemistry of the dissolution of Palladium in pressure-cyanide has not received considerable attention. At room temperature and pressures, the reaction between sodium cyanide and Palladium does not occur because of poor kinetics. However, at elevated temperatures between 100-160 °C, Palladium can be leached by sodium cyanide like the reaction of gold. A research study has been undertaken to develop the fundamentals of a method for the direct dissolution of Palladium In this work, the dissolution of Palladium powder and place were measured in pressure clear cyanide solution. The cyanide leaching reaction mechanism is also discussed. The data of Palladium powder and place at different cyanide concentrations, different temperature and different oxygen pressure are obtained. The dissolution rate of metal Palladium powder and place were found to be relate to the cyanide and oxygen level.

At room temperature and pressures, the reaction between sodium cyanide and platinum group metals (PGMs) does not occur because of poor kinetics. However, at elevated temperatures, PGMs can be leached by sodium cyanide like the reaction of gold. However, few rate expression which describe the leaching of Palladium in cyanide solution has been developed. In this paper, the rate of Palladium dissolution was measured in pressure clear cyanide solution using a Palladium rotating disk. The data at different rotation speed, cyanide concentrations, temperature and oxygen pressure are obtained. The dissolution rates were independent of rotation speed for oxygen-saturated solutions between 100-400rpm. With increasing temperature the dissolution rate is increased. With increasing cyanide concentration and oxygen pressure, the dissolution rate first increased to a maximum value and then decreased.

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