Nanomechanical Insight into Facet-Dependent Adsorption Mechanism of Flotation Collectors on Spodumene Surfaces

Gaining in-depth insights into the adsorption mechanism of collectors serves as the core scientific basis for achieving efficient spodumene (the most important lithium-bearing mineral) flotation. Due to the spodumene exhibits complex anisotropic surface properties, the quantitative understanding of the facet-dependent interaction between collectors and spodumene surfaces remains challenging. Herein, taking the typical collectors sodium oleate (NaOL) and dodecylamine (DDA) used in spodumene flotation separation, the chemical force microscopy technique was used to quantitatively measure the intermolecular interactions between collectors and different spodumene surfaces (110, 100, and 010) at the nanoscale. Adhesion measurements revealed that the adhesion forces of DDA with the (110), (100), and (010) surfaces were 21.7, 43.3, and 23.3 mN/m, respectively, with adhesion energies following the order (100) > (010) ≈ (110). Anisotropic adhesion was attributed to variations in the density of negatively charged O atoms on the surfaces. Conversely, the strong electrostatic repulsion between -COO- group and spodumene surfaces induced much weaker adhesion (1.7-8.8 mN/m) of NaOL toward all the surfaces. The adhesion energies between oleate ions and spodumene surfaces followed the order (110) ≈ (010) > (100), which correlated with differences in the number of exposed Al sites on the surfaces. Furthermore, the stronger adhesion between -NH₃⁺ group and spodumene surfaces enabled DDA to adsorb more stably and effectively onto them, thereby enhancing the surface hydrophobicity and facilitating spodumene flotation. This study provides quantitative insights into the facet-dependent adsorption of collectors on mineral surfaces at the nanoscale, offering significant potential for establishing a quantitative link between mineral flotation behavior and the interaction forces between collector molecules and mineral surfaces.