The use of AFM to study flotation parameters of Li bearing Engineered Artificial Minerals represented in slags

Due to the developments in electric mobility and the increased utilization of batteries, lithium has been classified as a critical raw material. It is a challenge to save and recycle existing lithium sources and the development of new recycling routes is a key area of research. A common method for the recycling of lithium ion batteries involves a pyrometallurgical high temperature treatment which concentrates critical elements in an alloy, whereas ignoble valuable metals such as lithium are concentrated in slags or dust. In order to use these Li-bearing slags as a promising lithium source, the priority programme PP2315 promotes the enrichment of lithium as engineered artificial mineral (EnAM). The most prominent Li-bearing EnAM is lithium aluminate which is found to be embedded in the gangue mineral gehlenite. The separation of these EnAM phases can be achieved via froth flotation, which is addressed in the presented project FlotEnAMIS as a part of the PP2315.
Froth flotation is a widely established separation process in the mining industry that is most efficient for particles in the size range of 20 μm – 200 μm. It is driven by the differences in the particle wettability and the attractive hydrophobic interaction between bubbles and particles at the solid-gas interface. This wettability difference can be controlled by selective adsorption of chemical reagents, such as collectors or depressants. Atomic force microscopy (AFM) can examine the differences in important driving forces of flotation acting between phases of certain hydrophobicity. For instance, colloidal probe AFM (CP-AFM) can be used as a model method to study the interaction of a sphere mimicking a bubble and a mineral surface.
The adsorption of surfactants on Li-EnAMs and the important sub-processes such as wettability, reagent adsorption, inter-particle interaction and bubble-particle interaction is investigated in this study by means of different AFM methods. The information obtained on the particle-reagent interaction is put in context with results of micro flotation studies. Based on this, suitable reagent regimes can be developed for the efficient recovery of lithium bearing minerals via flotation.