Theoretical calculation and experimental investigation on vacuum gasification separation of Ag-Cu-Au ternary alloy

Abstract

In this study, an innovative method for vacuum gasification separation of Ag-Cu-Au alloy was proposed. The saturated vapor pressure of each component is calculated theoretically, and the activities of Au-Cu and Ag-Cu-Au alloys are calculated by molecular interaction volume model (MIVM). The results show that the activities of Au-Cu alloy calculated by MIVM is accurate and reliable. Based on activity prediction, the separation coefficients of Au-Cu alloy were calculated. The results show that the separation coefficients of Au-Cu alloy are between 0.0037 ∼ 0.6626 in the temperature range of 1337–1773 K. Subsequently, the vapor-liquid equilibrium composition and vapor-liquid equilibrium phase diagram of Au-Cu and Ag-Cu-Au alloys were calculated, and the vapor-liquid equilibrium measurement experiments of Ag-Cu-Au alloy were carried out. The results show that vacuum gasification is challenging to realize the separation of Au-Cu alloy. During the vacuum gasification separation process of Ag-Cu-Au alloy, silver volatilizes into the vapor phase. When the pressure is 10 Pa and the mole fractions of silver, copper and gold in the liquid phase are 0.2, 0.1 and 0.7, respectively, the equilibrium temperature is 1545.5 K, and the mole fractions of silver, copper and gold in the vapor phase are 0.994, 0.002 and 0.004 respectively. The corresponding experimentally determined mole fractions of silver, copper, and gold in the vapor phase were 0.9666, 0.0333, and 5.89 × 10−5, respectively. In addition, the distribution and occurrence state of each element in the vacuum separation process of Ag-Cu-Au alloy were determined by EPMA.