Coupled mineral dissolution–precipitation regulates solution chemistry for calcination-free lithium extraction from α-spodumene under geothermal conditions

Conventional lithium extraction from α-spodumene requires energy-intensive calcination before leaching. Here, we demonstrate calcination-free lithium extraction under hydrothermal conditions by coupling NaHCO 3 -promoted α-spodumene dissolution with olivine-mediated secondary mineral precipitation, which efficiently removes Si and Al from solution. At 300 °C, the α-spodumene–olivine–NaHCO 3 system achieved 74.1 ± 2.6% lithium extraction after 6 h, compared with 39.7% for α-spodumene in NaHCO 3 solution alone and 2.0% in water. Olivine alone provided only limited enhancement, demonstrating the synergistic effect of NaHCO 3 -promoted spodumene dissolution and olivine-mediated secondary mineral formation for sustained lithium extraction. X-ray diffraction and electron microscopy show that smectite and a carbonate-bearing Na–Mg–Al–Si secondary phase formed predominantly on or near olivine particles rather than α-spodumene, thereby maintaining favorable conditions for continued lithium extraction. At 250 °C, the same dissolution–precipitation pathway remained effective, although the reaction proceeded with slower kinetics. These results demonstrate that coupled mineral dissolution–precipitation governs fluid evolution and enables calcination-free lithium extraction from α-spodumene under geothermal conditions. Carbonate-bearing secondary mineral formation additionally retained bicarbonate-derived inorganic carbon in the solid products.