Dual-anchoring mechanism of amide-carboxyl groups enables activator-free flotation separation of spodumene from feldspar

To address the challenge of difficult flotation separation between spodumene and aluminosilicate minerals, this work synthesized a long-chain carboxylic acid surfactant featuring amide groups, N-Oleoylglycine, as a high-performance collector. Experimental results demonstrate that N-Oleoylglycine exhibits significantly improved collecting power for spodumene compared to conventional sodium oleate, along with superior selectivity in distinguishing spodumene from feldspar. Under optimized conditions (5 × 10 −4 mol/L concentration, pH 7.0), N-Oleoylglycine achieved 89.39 % flotation recovery for spodumene, contrasted with merely 9.78 % for feldspar, highlighting its exceptional separation efficacy. Nuclear magnetic resonance (NMR) analyses reveal that the deprotonated amide nitrogen coordinated with Al 3+ ions on spodumene surfaces. Density functional theory (DFT) calculations further identify the amide and carboxyl groups as the primary functional groups responsible for its collector properties. DFT calculations also predict that in the adsorption configuration of N-Oleoylglycine with Al ions, the Al ions form complexes with the N atom of the amide group and two carbonyl oxygen atoms, respectively Multiple characterization techniques — including contact angle measurements, FTIR spectroscopy, and XPS analysis — collectively substantiated that N-Oleoylglycine achieves selective adsorption on spodumene through synergistic interactions between its amide and carboxyl moieties. Notably, the self-assembly capability of amide groups through intermolecular hydrogen bonds enables ordered collector molecular arrangement on mineral surfaces, suggesting potential for advancing mineral separation technologies.