Tajikistan University of Technology named after Academician M. S. Osimi, Dushanbe, Republic of Tajikistan:

T. D. Dzhuraev, Professor, e-mail: mcm45@mail.ru

F. K. Khodzhaev, Assistant

E. R. Gazizova, Assistant Professor

I. Sh. Muslimov, Assistant Professor, Chair of Metallurgy of Non-Ferrous Metals

Smelting reduction of lead concentrates leads to obtaining of lead bullion, containing up to 5% (wt.) of contaminants, such as copper, silver, gold, tin, antimony, arsenic, bismuth, etc. One of the simplest and most reliable methods of metal and alloy refining from contaminant elements' segregation is refining based on the change of solubility of melt components and their separation in both liquid and solid states in the density of resulting phases. There was made an offer to use thermodynamic calculations in the theory of regular solutions in the development of technologies for deep purification of lead from contaminants. At the same time, there was shown the mechanism of purification of segregation-crystallization lead refining. Crystallization refining occurs in lead-element systems. On the basis of thermodynamic calculations, there was created the diagram of lead state with boron, carbon, phosphorus, germanium, niobium and tungsten. Systems are characterized by complete immiscibility in liquid components and lack of solubility in the solid state. Mutual doping of lead by second components, as well as doping of second components by lead, does not change the melting point of the components. The consequent crystallization of each component occurs in these systems during melt cooling, depending on melting temperatures.

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