Distribution of antimonium chalcogenides under conditions of vacuum thermal processing of mattes

Abstract

It was established based on the analysis of the results of published works and the results obtained by the authors that there is no information on the behavior and distribution of antimony chalcogenides - Sb2S3, Sb2Se3, Sb2Te3, as well as double systems - Sb2S3-Sb2Se3, Sb2S3-Sb2Te3 and Sb2Se3-Sb2Te3 under the vacuum processing conditions for polymetallic mattes performed at 1100-1250 °C and a vacuum of 15 - 0.7 kPa. It was found based on the saturated vapor pressure values for monochalcogenides that the vapor pressure of free antimony sulfide will be 58.95 kPa at 1100 °C, i.e. the lower limit of the technological interval, which indicates its complete transfer to the vapor phase when the mattes are evacuated; the vapor pressure of free antimony selenide at 1100 °C exceeds the atmospheric pressure value (101.3 kPa), and Sb2Se3 would be completely extracted into the vapor phase in vacuum; the boiling point of liquid antimony telluride at atmospheric pressure corresponds to 971 °C, and it would be extracted into the vapor phase under the conditions of matte evacuation. The thermodynamic evaporation characteristics of antimony chalcogenides were found. It was concluded based on the location of the boundaries of the liquid and vapor phase coexistence fields that it is impossible to separate binary systems of antimony chalcogenides into separate compounds in the process of one evaporation cycle – condensation, in binary systems. Different effects of pressure reduction over melts were found. Lowering the pressure from atmospheric one to 0.7 kPa in Sb2S3-Sb2Se3 system did not change the position of the boundaries of the liquid and vapor fields (L + V) under the temperature; field width (L+V) decreases with decreasing pressure in Sb2S3-Sb2Te3 system; the field width first decreases with temperature, then increases in system Sb2Se3- Sb2Te3. At the same time, the position of the boiling curves of antimony chalcogenide solutions indicates the complete transfer of compounds into the vapor phase under the conditions of matte distillation processing (at 1100-1250 °C) at atmospheric pressure which is important for assessment of the distribution of antimony and rare metals - selenium and tellurium by processed products.