Highly efficient lithium leaching from α-spodumene via binary composite salts low-temperature roasting process

With the rapid development and widespread application of lithium-ion batteries, the demand for lithium has surged dramatically, drawing increasing attention to its extraction from spodumene deposits. However, the sustainable development of the lithium industry faces challenges, as traditional processes are hindered by high conversion temperatures, excessive acid consumption, and difficulties in purifying the leachate. Hence, we propose a binary composite additive system based on sodium sulfate‑calcium oxide (Na₂SO₄-CaO) for roasting α-spodumene at comparative low temperatures. The optimal roasting conditions entailed a mass ratio of spodumene/CaO/Na₂SO₄ at 1:0.1:0.8, a roasting temperature of 900 °C, a holding time of 2 h, a liquid-to-solid ratio of 5 mL/g, and leaching at 60 °C for 30 min, resulting in an impressive lithium leaching efficiency of 95.45 %. Thermodynamic and kinetic analyses reveal that the roasting formed the product of water-soluble LiNaSO₄, which was then dissolved into water, with the leaching process being governed by internal diffusion.