Thermodynamic criteria of alloying elements elimination during recycling end-of-life zinc-based products by remelting

Abstract Elimination of alloying elements in the end-of-life (EoL) zinc-based products is essential for the resource efficiency of zinc recycling. Using a thermodynamic method, the elimination behavior of 34 alloying elements during the recycling of EoL zinc-based products by the remelting process was quantitively evaluated. The influence of all the thermodynamic parameters was considered and extensively discussed. It was found that the remelting process with treatment using chloride flux or oxide slag is efficient in alloying elements elimination. However, eliminate alloying elements, such as antimony, bismuth, cadmium, cobalt, copper, germanium, gold, indium, iron, lead, nickel, silver, and tin is difficult. These elements will contaminate the remelted zinc metal once mixed in the collected EoL products. Moreover, promoting the elimination of these alloying elements is difficult by adjusting the remelting conditions such as temperature, chlorine partial pressure, and flux composition. To increase the recycling efficiency of zinc, in addition to improving metallurgical refining technology, establishing an advanced recycling system to achieve a horizontal alloy-to-alloy recycling and changing the current trend of product design of excessive mixing is essential. The thermodynamic criteria of alloying elements elimination can provide basic information for these tasks.