Amide group enhanced self-assembly and adsorption of dicarboxylic amino acid surfactants on a rhodochrosite surface through intermolecular weak interaction

Efficient recovery of fine mineral particles is challenging for minerals flotation due to a small particle mass and high specific surface area. This work innovatively applied a multifunctional surfactant 2-dodecanoylamino-pen-tanedioic acid (DPA) for achieving flocculation and recovery of fine rhodochrosite. Interestingly, the formation of larger aggregation induced by DPA, instead of sodium oleate (NaOL), was observed and the medium particle size (d50) was 2.29 times than that of NaOL, resulting in more strong collecting ability for fine rhodochrosite particles (with a recovery of 82.5% for 0.1 mmol/L DPA and 35.3% for 0.1 mmol/L NaOL). Analysis with EDLVO theory illustrated that the hydrophobicity force is one of the factors that induces hydrophobic flocculation, along with electrostatic repulsion, the Van der Waals force, and weak interaction. Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculations revealed the "weak-to-medium" hydrogen bond formation among the amide groups or amide and carboxyl functional groups in the DPA complex, further enhancing aggregation between rhodochrosite fine particles. These discoveries are beneficial for providing new insights into aggregation generation among fine particles in the presence of surfactants containing multiple functional groups.