Purification of Crude Selenium and Recovery of Gold and Silver by Vacuum Distillation

In this paper, vacuum distillation technology was developed to purify crude selenium produced by the hydrometallurgical selenium removal treatment of copper anode slime and recover gold and silver. Theoretical analysis of the saturated vapor pressure was performed to determine the feasibility of vacuum distillation. Laboratory and semi-industrial experiments were carried out to determine the optimum process parameters. The kilogram-scale experiments showed that the purity of selenium can be increased from 91.35 to 98.91% under the conditions of 50 Pa, 693 K, and 90 min. It is difficult to separate selenium and tellurium completely by vacuum distillation. The semi-industrial experiments showed that when the feed mass was 100 kg, under the conditions of 50 Pa, 693 K, and 160 min, the daily output of refined selenium was more than 350 kg, the comprehensive power consumption for producing refined selenium (per ton) was 587 kW h, the direct yield of Se was 96.78%, and the direct yields of Au and Ag were 99.72% and 99.56%, respectively, representing enrichment by more than 20 times. The process is an environmentally friendly and efficient metallurgical cleaning process in the treatment of crude selenium.