Adsorption behavior of fatty acids during high-density conditioning for spodumene flotation

The growing demand for electric vehicles and lithium-ion batteries is driving the development of new lithium projects. Spodumene, the primary lithium bearing mineral, is found in pegmatite deposits and is often recovered by froth flotation with fatty acid collectors. These collectors are known for poor selectivity, often recovering other silicate gangue minerals due to their similar surface properties when conditioning is poorly executed. High-density conditioning is a favored approach to achieve desired spodumene flotation performance with tall oil fatty acids, but the mechanisms at play during this stage are largely unknown. This study combined batch flotation with real ore samples and Time of Flight-Secondary Ion Mass Spectroscopy (ToF-SIMS) and X-ray Photoelectron Spectroscopy (XPS) analysis with single minerals, to understand the fatty acid adsorption behavior during conditioning in relation to spodumene flotation performance. The ToF-SIMS results revealed a high amount of physisorbed molecular fatty acid is needed for high spodumene recovery, but physisorption decreased as conditioning progressed, reducing lithium recovery and improving selectivity – an observation validated with two different spodumene ores. This study provides strong evidence that physical adsorption of molecular fatty acid alongside chemisorption of the fatty acid anion, either independently or as an acid-anion complex, are required on spodumene at an ideal ratio for desirable flotation performance.