Increasing demand for lithium-ion batteries has led to the development of several new lithium mineral projects around the globe. Some major mineral processing challenges these projects face are similarities in gangue and value mineral behaviour and poor selectivity in froth flotation. Unsaturated anionic fatty acids are the primary spodumene flotation collectors, known to be strong collectors with poor solubility and selectivity. Fundamental flotation research consensus is that spodumene flotation is driven by a fatty acid–anion complex adsorbed at cationic aluminum sites. However, many small-scale studies result in poor recoveries, prompting several researchers to investigate cationic activators or mixed anionic/cationic collectors to improve flotation performance. Testwork with real spodumene ore is rare in recent literature, but older publications from several deposits prove that fatty acids can successfully concentrate spodumene. The process generally includes alkaline scrubbing, high-density fatty acid conditioning, and flotation at pH 7.5–8.5 with 500–750 g/t fatty acid collector. The collector speciation behaviour is notably sensitive to pulp conditions around this pH; possibly resulting in unstable flotation circuits and inconsistent results. This paper reviews fatty acid collector properties and the available industrial and fundamental spodumene flotation research. We aim to provide new insight for understanding particle-collector interactions in spodumene flotation and help bridge the gap between fundamental and industrial processes which will be needed to de-risk projects in the growing lithium mineral industry.

Lepidolite flotation testwork was performed on 21 variability samples from the EMILI deposit in Allier, France, with head assays ranging from 0.49 to 1.38% Li2O and an average K80 of 236 mm. After desliming, flotation was performed with an amine collector which was able to produce lepidolite concentrates grading >4.2% Li₂O with over 74.6% Lithium recovery from 13 samples - often without cleaner flotation. The lower grade lepidolite concentrates (<4.2% Li2O) were a result of unwanted recovery of other mica-type gangue minerals, as well as low feed grades below the 0.8% Li₂O cut-off grade already excluded from the mine plan.

Spodumene is the primary Lithium mineral, however, other minerals like lepidolite, petalite, zinnwaldite, and Li-clays are gaining importance. Different processing approaches are needed to address different challenges. Dense Media Separation (DMS) can concentrate spodumene and petalite, but recoveries are often limited by grain size. Froth flotation is widely used to concentrate spodumene and is the main lepidolite beneficiation method, where spodumene is floated with anionic fatty acids and lepidolite with cationic amine collectors. Zinnwaldite, a high-iron lepidolite mineral, can utilize magnetic separation and to some extent, flotation, whereas and Li-clays (e.g., hectorite and illite) are primarily concentrated through size classification.

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.