Efficient recovery of critical elements by creating artificial minerals in slags

The scarcity of raw materials, especially rare earths, lithium, tantalum and vanadium, is a significant risk factor in today's society. Geological reserves of these elements are not sufficient to meet future demand. By recovering these elements from material waste streams, an independent second source of raw materials can be created. Such a second source can be created by capturing the critical elements in a phase with good separation properties through the production of engineered artificial minerals (so-called EnAMs). This approach can be used for the recovery of critical elements from slags resulting from pyrometallurgical processing.

In addition to industrial slags (e.g. Umicore), synthetically produced slags were also studied to investigate the crystallization behavior of Li, Ta and V and to identify potential EnAMs. Specific modifications (chemistry, heat supply, atmosphere) have been used to study how critical elements are incorporated into artificial phases during slag solidification. The example of Li shows that different EnAMs (LiAlO₂ and LiMnO₂) can act as potential sources of recovery. Preliminary investigations have shown that the formation of LiAlO₂ can be inhibited by other phases. For instance, due to the increasing use of lithium-manganese rich cathode material, additionally manganese enters the system, resulting in the preferred formation of spinels (MgAl₂O₄) instead of LiAlO₂. As aluminum can largely be eliminated via mechanical processing, in this study, LiMnO₂ was investigated as a potential main EnAM for the recovery of lithium. Since manganese is highly redox-sensitive, the investigation of speciation changes in the high temperature range of slag is important.