Development of Atomic Force Microscopy based interaction scanning modalities for the assessment of the flotation separation of Lithium bearing engineered artificial minerals in slags

Froth flotation is a widely established heterocoagulation separation process for the raw materials industry that is most efficient for particles in the size range of 20 μm – 200 μm. It is becoming even more important in upgrading critical materials. The key selection criterion is the difference in (de)wett(ing)ability of the surfaces of particulate phases. It has always been a grant challenge to quantitatively asses this complex physicochemical surface property. Most typically single mineral microflotation tests are found practical. They are further applied to find suitable reagent regimes necessary to condition the suspended particles in order to make selective separation possible. This involves various different suits of chemicals referred to as collectors and regulators. It is challenging if not impossible to obtain enough sample materials of pure individual phases to perform those conventional microflotation tests with unconventional resources, such as slags containing engineered artificial mineral (EnAM) phases enriched with critical elements. A prominent Li-containing EnAM is Lithiumaluminate and engineered in Al2O3-CaO-Li2O-MgO-(MnO)-SiO2 slag systems from battery recycling. We propose and develop an Atomic Force Microscopy based Interaction Scanning approach to be able to obtain surface interaction parameters at high resolution which are decisive for the particle-bubble-(non)attachments related to the dewettingability contrast.

As typical artificial phases in the mentioned slag system, we synthesize the valuable Lithiumaluminate and the gangue Gehlenite with high temperature sintering for evaluating interaction parameters and performing conventional microflotation tests of pure EnAM specimen. For assessing different key surface interactions from reagent regime depending surface potentials and surface hydrophizations we perform different hydrophilic and hydrophobic colloidal probe AFM measurements in dry and liquid mode on a representative model system with the valuable Lithium bearing mineral Spodumene and the representative gangue phase Quartz as substrates. This model system occurs in nature and is suitable to study reagents for efficient separation of Li-bearing minerals by flotation and to relate them to artificial phases such as EnAMs. The AFM studies are set in context with common micro flotation experiments and further characterization techniques. With this we will showcase and discuss the potentials of an Atomic Force Microscopy based approach to flotability assessment.
This project is part of the priority program PP2315 on engineered artificial minerals and their processing of the DFG (German Research Foundation).