Silver Silver Antimony Lead Antimony Alloy Vacuum Distillation Enrichment Research

Silver and antimony are provided with a lot of excellent properties, and they are widely used in military project, electron, machinery and some other industries. Along with the continuous consumption of silver and antimony resources, it is particularly important to recover silver and antimony synthetically from their resources. Lead anode slime with high antimony is a kind of important raw material which may synthetically recover valuable metal such as silver and antimony. At present, the main treatment processes are pyrometallurgical process and hydrometallurgical process. But these processes both have drawbacks such as low direct recovery rate of metals, a mass of slag, long process flow, great investment, great consumption of reagent, less technologic adaptability, et al. Based on the advantages of vacuum metallurgy, which has characteristic of high metalic recovery rate, simple technological process, without wastewater and emissions produced in the metallurgical process. To improve metalic synthetically recovery rate and reduce environmental pollution which could cause by smelting process, Ag-contained lead-antimony multi-component alloys, produced after primary smelting of lead anode slime with high antimony, was studied by vacuum distillation in this work.The traditional treatment methods of lead anode slime and the application of vacuum distillation in metal separation were introduced in this paper. Thermodynamics and kinetics analysis of Ag-contained lead-antimony multi-component alloys separation by vacuum distillation were conducted too. Vacuum distillation experiments of Ag-contained lead-antimony multi-component alloys for discussing the volatile behavior of metal elements in the process of distillation were carried out at860-1100℃. Enrichment regularity of silver and influencing factor of enrichment effect were obtained. At the same time, experimental studies also conducted for crude Sb preparation by vacuum distillation this kind of alloys at650-870℃.Thermodynamics research shows that:volatile element boiling point sequence from high to low is Cu> Ag> Pb>Sb> Bi>As. The saturated pressure of pure substances of As, Sb, Bi, Pb are104～1013times bigger than Ag. The saturated pressure of pure substances of Cu is bigger than Ag. So volatility of As, Sb, Bi and Pb is far outweigh that of Ag and Cu. From the separation coefficient calculated results of Ag-i binary system, it can be seen that the separation coefficient βCu-Ag relatively close to1and other βi-Ag is much more than1. Sb, Bi and Pb can be separated preferably from Ag and they will volatilize into gas phase. The vacuum distillation separating effect of Ag-Bi binary system precede that of Ag-Sb and Ag-Pb binary system. It is known from binary phase diagram that lots of intermetallic compound phases, which will slow down the spread of Sb atoms in liquid alloy, could be formed with the distillation temperature increasing. It will cause the incomplete evaporation of antimony and arsenic.Experimental results showed that distillation temperature and heat preservation time had significant effect on both enrichment of Ag and Sb at a chamber pressure of5Pa～35Pa for30min when the temperature range of860-1100℃. Evaporation of Ag and Sb was more remarkable with the increase of distillation temperature and extension of heat preservation time. The volatilization rate of bismuth and lead was over99%when the distillation temperature was more than950℃. The silver concentration rate was more than99.28%in the heat preservation time range of30min-120min at950℃. Silver content in residual alloy increased from21.65%to28.3%after vacuum distillation. It was nearly8times compared with silver content in raw material. The volatilization rate of antimony and arsenic, which were influenced by Cu and Ag in residual alloy, maintained at96.3%and92.5%respectively when the heat preservation time was equal or greater than45min.Results of experimental, which were conducted at a chamber pressure of5Pa～200Pa for60min-240min at650～870℃, showed that crued antimony could obtain by vacuum distillation with Ag-contained lead-antimony multi-component alloys. The volatilization rate of antimony could reach80%. However, the existence of Pb, Bi, As and Cu in the multi-component alloys significant effected enrichment result of antimony. Antimony content in crude antimony was more than95%after three times vacuum distillation, but direct recovery rate of every time was less than80%.