Selective Lithium extraction from clay minerals using a Superacidic urea–Methanesulfonic acid deep eutectic solvent

Urea–methanesulfonic acid (MSA) deep eutectic solvents (DESs) are reported here for the first time as a green, superacidic platform for the highly selective extraction of lithium (Li) from clay-bearing ores. Formulated in molar ratios from 1:2 to 1:8, these DESs were characterized using Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, 1 H and 13 C nuclear magnetic resonance (NMR), ultraviolet-visible (UV–Vis) spectroscopy, alongside density functional theory (DFT) to map their unique molecular interactions and tuneable acidity. Spectroscopic and computational analyses revealed a transition from hydrogen-bond-dominant to ionic environments as the MSA ratio increased, with DFT indicating rising interaction energies (1.583 to 3.237 eV) and vibrational signatures of protonation. The urea-MSA 1:2 system, optimized with 20% water, maintained superacidity ( H 0 = −3.102) and achieved a remarkable 100% extraction efficiency for Li, Na, and Sr. Critically, the system exhibited superior selectivity, recovering 100% Li while leaching only 23% Al and 6% K, significantly outperforming conventional sulfuric acid (4% Li) and citric acid (92% Li). This selectivity is attributed to a “coordination window” where the superacidic protons effectively disrupt the mineral lattice while the DES components inhibit the total dissolution of structural impurities. These findings demonstrate that urea-MSA DESs serve as high-performance, recyclable, and sustainable alternatives for the selective recovery of critical metals. By operating at moderate temperatures with high atom economy, this system offers a viable industrial pathway for the green valorization of complex mineral matrices, addressing the urgent need for sustainable lithium sourcing in the global energy transition. • Urea-MSA DESs formulated and characterized across 1:2 to 1:8 ratios. • FTIR, Raman, and NMR show a shift from H-bonding to an ionic environment. • Pure DESs exhibit superacidic behavior: H 0 from −3.501 to −5.681. • Achieved 100% Li, Na, and Sr extraction from complex Serbian clay-hosted ore. • High selectivity for Li over structural gangue elements like Al (23%) and K (6%). • DFT analysis links molecular reactivity descriptors to macroscopic leaching performance.