Vacuum Distillation And Separation Of Lead Platinum And Palladium Alloys

The recovery of Pt and/or Pd using lead as the collector is an effective method to treat waste materials containing Pt and/or Pd. But the traditional methods (i.e. cupellation, nitric acid leaching) for separation of bullion lead containing Pt and Pd are faced with several problems (e.g. serious pollution, low direct recovery of metals), so it is necessary to study a clean technology. The vacuum metallurgy has advantages such as short process flow chart, high efficiency and clean to the environment. From this point of view, the vacuum separation of Pb-Pt, Pb-Pd and Pb-Pt-Pd alloy were studied in this paper.Theoretical analyses indicate that Pb-Pt, Pb-Pd and Pb-Pt-Pd alloys could be separated by vacuum distillation. The effects of distillation temperature, distillation time and pressure on the vacuum separation of Pb-Pt, Pb-Pd and Pb-Pt-Pd alloys were studied. The results of experiments are listed as fellows:(1) The removal ratio of Pb was more than 99.88% and Pt content in residues was higher than 99% when the Pb-Pt alloy containing 2.5%～15% Pt was distilled for 3 h at 1250 K and 30 Pa.(2) The primary distillation results of Pb-Pd alloy show that the removal ratio of Pb was close to 92.5% and the Pd content in the primary distillation residue remained about 60% when the Pb-Pd alloy containing 10% Pd was distilled for more than 4 h at 1250 K and 35 Pa. After the secondary distillation at 1523 K, the Pd content in the secondary residue still maintained about 60%. In the vacuum distillation process of Pb-Pd alloy, most of Pb could be separated and collected as metallic Pb, while Pd was enriched in the residue. As a result, the material amount of further treatment for extraction of Pd was reduced remarkably by this method.(3) The primary distillation results of Pb-Pt-Pd alloy show that the removal ratio of Pb was close to 92.6% and Pt+Pd content in primary distillation residue remained around 60% when the Pb-Pt-Pd alloy containing 5% Pt and 5%Pd was distilled for more than 2 hours at 1250 K and 30 Pa. After secondary and thirdly distillation at 1523 K, the Pt+Pd content in secondary and thirdly residue were 67.23% and 68.98%, respectively. In the process of vacuum distillation of Pb-Pt-Pd alloy, most of Pb can be separated and collected as metallic Pb, while Pt and Pd are enriched in residue. As a result, the material amount of further treatment for extraction of Pt and Pd is reduced remarkably by this method.