New vacuum distillation technology for separating and recovering valuable metals from a high value-added waste

Flotation tailings of copper-anode slime is a high value-added waste. A new, clean and highly efficient vacuum distillation process is presented for the separation of valuable metals that remain in the waste. In this work, the saturated vapor pressure of each metal element in the flotation tailings is theoretically analyzed, with vapor-liquid equilibria (VLE) diagrams used to quantitatively predict the composition of the products. The optimum distillation temperature and time of volatilization behavior of each component are investigated using a two-step, low-temperature and high-temperature vacuum distillation experiment; the system pressure of both steps is 1-5 Pa. The experimental results indicate that the recovery efficiencies of Se and Te are 98.09% and 97.82%, respectively, after the low-temperature distillation (923 K and 120 min); the removal rates of Pb, Sb and Bi are 92.99%, 96.86% and 94.57%, respectively. The recovery efficiencies of Cu, Ag and Au are 95.65%, 99.28% and 99.12%, respectively, after the high-temperature distillation (1173 K and 50 min). Valuable metals in the flotation tailings can be separated and recovered effectively via a two-step vacuum distillation in which no wastewater or gas is released into the environment, meeting the development needs for cleaner production within the metallurgical industry.