Effect of copper collector form on recovery of suspended platinum and palladium metals in the Al₂O₃-CaO-SiO₂ slag at 1723 K

PGMs (Platinum group metals) used as catalyst which reduces toxic substances in emission gas exhausted from an automobile should be recycled because they are precious metals produced only at the limited regions and scarcity. Rose process is employed to recover the platinum group metals from spent catalytic converters. The recycling process is to smelt an alumina honeycomb, in which PGMs are coated, with Cu, Cu₂O, reductants and flux such as lime and silica. This study compared the recovery ability of the extractant of Cu or Cu₂O for suspended platinum or palladium particles in the Al₂O₃-CaO-SiO₂ molten slag. The collector material of Cu or Cu₂O was added to the suspended PGM particles in the slag, the time dependence of platinum and palladium concentrations in the slag was investigated at 1723 K under carbon saturation. It was found that the Cu₂O addition shows higher recovery of platinum and palladium than the metallic Cu. Copper oxide dissolved in the slag was reduced to metallic copper in the slag and alloyed with the suspended PGM particles to form the liquid Cu-PGM system. As the result, the particle size of the PGM increases and sedimentation rate in the slag is promoted.