Selective extraction of lithium from the clay-type lithium ore by a novel process of blank roasting and CaO-aided alkaline leaching

Abstract

With the explosive demand for lithium and the depletion of high-quality lithium resources, the extraction and utilization of lithium from clay-type lithium ore have become increasingly significant. In this research, a clay-type lithium ore composed of diaspore, goethite, kaolinite, illite, and cookeite (LiAl₄(AlSi₃O₁₀)(OH)₈) was used, and lithium mainly situated in the structure of cookeite. To destroy the cookeite structure and selectively extract lithium from it, a novel and green process of blank roasting and CaO-aided alkaline leaching was proposed. After roasting at 800 °C and leaching with CaO/roasting powder mass ratio of 0.35 and NaOH concentration of 3 g/L at 100°C, the leaching efficiency of Li could be 82.84 %, while those of Al, Si, Mg, and Fe were only 0.030 %, 0.013 %, 0 %, and 0 %, respectively. Li₂CO₃ with a purity of 99.85 % was precipitated after the purification of the leaching solution by a solvent extraction method. In the view of structural transformation, cookeite was decomposed and transformed into LiAlSi₂O₆ in roasting, which was then disrupted by OH^– and released lithium in CaO-aided alkaline leaching, along with the formation of solid Ca₃Al₂O₆·6H₂O and Ca₃Al₂SiO₄(OH)₈. Thermodynamic equilibrium calculation results indicate that adding CaO and NaOH and maintaining the pH at 12.6 ∼ 12.9 can immobilize Al and Si and inhibit the leaching of Mg, Fe and Ca, which is the key for the efficient and selective extraction of lithium.