Simulation prediction and experimental study of phase equilibrium for Ag−Cu and Ag−Sb binary alloys in vacuum distillation

Abstract

The modified molecular interaction volume model (M-MIVM) was used to calculate the activity values and their deviations from experimental data for Ag−Cu and Ag−Sb binary alloys. Subsequently, theoretical vapor−liquid equilibrium phase diagrams (T−x−y and p−x−y) were plotted via combining M-MIVM and vacuum theory. The vapor−liquid phase equilibrium (VLE) experiments were conducted on the Ag−Cu alloy at 1500−1560 K and 10−15 Pa and Ag−Sb alloys at 950−1350 K and 10 Pa. The results showed that the average relative deviation and average standard deviation of activity were lower than 5% and 0.02, respectively. A comparison of theoretical and experiment results for VLE revealed that the simulated data on the T−x−y diagram were well consistent with experimental values. Therefore, the VLE phase diagrams can serve as a guide in vacuum separation experiments and industrial production for Ag−Cu and Ag−Sb binary alloys.

1. Introduction

Silver, a white metal, boasts unique properties such as corrosion resistance [1] and stability [2]. It finds application in various fields, primarily in the electronic industry [3], photography [4], aerospace engines and so on. Silver also plays a significant role in the financial sector [5] and has a rich history as currency, spanning millennia. It continues to hold value as a collectible currency, while also being extensively consumed in the creation of female ornaments [6]. Moreover, silver is widely employed in high technology, e.g., as a contact in chips and fuses due to its excellent conductivity [7,8], good flexibility [9], and high performance. Meanwhile, it is one of primary metals applied in medicine [10]. In ancient times, silverware was used to detect the presence of poisons in food. This is because the arsenic trioxide contains sulfur and its complexes that form black compounds with silver. In 2022, the global demand for silver reached 38000 t, but the real production was limited to 26000 t, indicating an oversupply situation [11]. Therefore, it is urgent to search for an efficient way of producing silver so as to fulfill societal needs.

The vacuum approach with advantages of short flow [12], high efficiency [13] and environmental friendliness [14] is extensively utilized in the extraction of precious metals, including silver and gold, from heavy colored anodic sludge [15,16]. When designing vacuum distillation experiments or industrial production routes for an alloy, the reliable VLE diagrams are essential for estimating the temperature and separation efficiency during alloy separation [17]. Therefore, adequate VLE data are crucial. They provide an intuitive and convenient approach for analyzing distillation and other vapor−liquid separation processes, making them widely applicable in the chemical industry [18]. However, the industrial alloy separation primarily involves multiple components, for which experimental data are often scarce and challenging to obtain through experimentation. Thus, the theoretical prediction [19,20] is an efficient method for acquiring the thermodynamic properties of multivariate alloys.