Structure-activity relationships in lithium-hosting montmorillonite: Octahedral lithium locking mechanisms

The structural complexity of lithium-bearing clay minerals and limitations of conventional characterization methods impede efficient lithium extraction from montmorillonite-type ores. This study employs density functional theory to elucidate structure-activity relationships governing lithium occurrence in montmorillonite, with particular emphasis on octahedral locking mechanisms and interfacial reaction barriers. Systematic calculations reveal four potential lithium occurrence sites: Al-O octahedra, Si-O tetrahedral lattices, interlayer sites and Li substituted H site. Lithium demonstrates optimal stability within Mg-Al-O octahedral lattices, exhibiting the lowest interaction energy (−672.982 kJ/mol) and substantial Mulliken charge transfer (2.35 e), confirming this configuration as the primary hosting environment. Density of states analysis uncovers critical electronic structure features: the 1s orbital of lithium remains energetically isolated from the Fermi level, explaining its chemical inertness and resistance to direct leaching. Conversely, the reactive 2p orbital of oxygen near the Fermi level facilitate surface interactions with flotation reagents. These electronic signatures imply the feasibility of flotation recovery alongside hydrometallurgical approaches. The octahedral locking mechanism originates from Li-induced dynamic symmetry reconstruction. This process achieves energy minimization through bond-angle regularization, while the notable contraction of Al-O/Mg-O bonds enhances electrostatic coupling. These synergistic effects ultimately establish a structural-charge dual-locking mechanism. This study delivers atomic-level insights into lithium occurrence mechanisms, addressing critical gaps in clay-type lithium mineralogy and revealing structure-activity relationships that guide sustainable lithium recovery via interface regulation.