Lithium Recovery from a Clay-Type Ore by Pressure Leaching Oxidation: A Kinetic Study

The increasing demand for lithium in energy storage technologies has renewed interest in clay-type deposits as alternative resources to brines and hard rock ores. This study investigates the leaching behavior of a Mexican clay-type lithium ore through conventional, hot, and pressure leaching using sulfuric acid. Mineralogical characterization (XRD and SEM–EDS) revealed that montmorillonite (~56 wt.%) is the primary lithium-bearing phase. Conventional leaching with 1–8 M H2SO4 resulted in limited lithium dissolution (<30% after 24 h), whereas hot leaching at 80 °C increased extraction to ~39%. Pressure leaching with oxygen overpressure significantly enhanced lithium dissolution, achieving ~64% within 180 min under 8 M H2SO4 and 80 °C. Kinetic modeling using a pseudo-first-order model accurately reproduced the extraction profiles, yielding increasing rate constants and equilibrium conversions with temperature. The low activation energy (~12 kJ·mol−1) indicates that lithium dissolution proceeds through weakly activated reaction–solution interactions rather than diffusion through a product layer. These findings provide a mechanistic basis for understanding lithium release from clay-hosted ores and highlight the importance of optimizing acid concentration, temperature, and oxygen availability to improve hydrometallurgical processing of clay-type lithium deposits.