Processing the Sb-Pb-Ag Alloy by the Distillation Method

The topicality of this work is due to the necessity of developing environmetally safe, highly efficient, and economical complex vacuum distillation technology for processing lead-containing middlings and wastes, in particular, the alloy fabricated when recovering the silicate slag of smelting copper-electrolyte slime (SPA) with the purpose of fabricating commerical monoelement concentrates of antimony, lead, and silver. Laboratory investigations into processing the SPA alloy and caclualtoins of temperature-composition (T-x) equlibrium phase diagrams (vapor-liquid equilibrium (VLE)) for analyzing the behavior of Sb-Pb and Pb-Ag binary alloys during processing; the preliminary selection of temperature and pressure in the system; and the separation efficiency of components under conditions of T = 900-2100 K, P = 1-133 Pa, and = 8-16 h are performed. The influence of temperature and pressure in the system; sublimation duration on the recovery completeness; and degree of separation of antimony, lead, and silver from the SPA alloy is investigated. When constructing equilibrium VLE phase diagrams, activity coefficients of binary alloys are calculated using the molecular volume interaction model (MVIM). Information is found on the influence of temperature and vacuum depth on the degree of sublimation and separation of metals from Sb-P and Pb-Ag formulations of various compositions. Saturated poar pressures are calculated for Sb (p* = 273.664-67436.9 Pa), Pb (0.149-485.9), and Ag (5.054 x 10(-5)-6.558) at T = 1073-1773 K. It is shown that high ratios = 1832.98-138.79, = 2948.16-74.09) and separation coefficients (log(Sb) = 2.099-3.33 and log(Pb) = 1.813-3.944) give the theoretical prerequisites for the selective isolation of these metals by vacuum distillations when antimony and lead are sequentially enriched in the gas phase ((Sb) > 1, (Pb) > 1), and for, silver, in the liquid phase. It is established that the molar fraction of poorly sublimable lead/silver in the gas phase y(Pb)/y(Ag) = (1.55-982) x 10(-3)/(36-772) x 10(-3) increases with an increase in temperature 894-1601/1399-2099 K, pressure 1.33-133 Pa, and metal content in alloy x(Pb)/x(Ag) = 0.9-0.9999/0.9-0.99. Activity coefficients for antimony (Sb) = 0.832-0.999, lead (Pb) = 0.474-1.0, and silver (Ag) = 0.331-0.999 for Sb/Pb and Pb/Ag alloys of the composition 0.1-0.9/0.9-0.1 in the temperature range under study are calculated using MIVM. The practical significance of revealed dependences of the amount and composition of sublimation products of polymetallic alloys on the mentioned process parameters is caused by the development of the principal processing technology of the SPA alloy by vacuum distillation.