A Novel Method for Clean and Efficient Separation and Recovery of Silver and Cadmium from Silver-Cadmium Alloy

Abstract

Alloy of silver and cadmium is used for low melting point fibers and electrical contacts because of its outstanding properties. Recycling silver-cadmium secondary resources is valuable but poses significant cadmium pollution challenges. The cadmium in silver-cadmium alloy can be removed through traditional processes such as electrolysis and oxidative roasting. However, cadmium will enter the wastewater or be released directly into the atmosphere, leading to significant environmental contamination. In the present study, we analyzed the feasibility of recovering silver-cadmium alloy through vacuum method from a theoretical perspective. Based on the model of molecular interaction volume model (MIVM), calculations are performed to determine the separation coefficient (β) and the composition of silver-cadmium alloy in vapor-liquid equilibrium at different temperatures. Utilizing the vapor−liquid equilibrium (VLE) theory, we have constructed a T-x(y) phase diagram of the silver-cadmium alloy in vacuum distillation. It shows that high temperature is not conducive to the separation of silver and cadmium. During the evaporation process, cadmium has much more evaporation than silver. However, when the content of cadmium in the liquid phase is reduced, it will promote the evaporation of silver. In addition, the experimental validation of the vacuum evaporation-multistage condensation method was conducted. The results of the optional experimental conditions suggest that the separation rate of cadmium is above 99.95%, and the purity of silver is more than 99.995%. The proportion of silver in the residue is stable at more than 99%. The direct recovery rate of cadmium was stable above 99%. This research presents a method that is both effective and environmentally friendly for the extraction of silver-cadmium alloy, which has high industrial production value.

Keywords: Silver-cadmium alloy, Molecular interaction volume model (MIVM), Vacuum separation, Vapor−liquid equilibrium (VLE), High-purity silver and cadmium