Direct lithium extraction from α-Spodumene using NaOH roasting and water leaching

The conventional method for extracting Li from the primary mineral source of Li (i.e., spodumene) involves complex and energy-intensive processes, including the conversion of naturally occurring α-spodumene to leachable β-spodumene through high-temperature calcination, followed by sulfuric acid baking, and water leaching. To address the economic and environmental challenges associated with the conventional method, this paper presents a patent-pending process for the direct extraction of Li from α-spodumene. This innovative method entails low-temperature roasting with NaOH to convert α-spodumene to water-soluble Li-bearing phases, from which Li is recovered through water leaching. This paper studies the process chemistry, thermodynamics, and kinetics, and further optimizes its parameters to maximize Li recovery. The roasting process promoted the alkali-silica reaction at about the melting temperature of NaOH (318 °C), producing water-soluble LiNaSiO₄ phase, eliminating the need for high-temperature calcination and acid-baking processes. The roasting reaction followed shrinkage core model. The exothermic water leaching reaction exhibited fast kinetics, achieving maximum Li recovery within one minute at room temperature. The regeneration of NaOH radicals during the water leaching yielded product solution with a pH of approximately 13, reducing chemical consumption in downstream purification. Based on the obtained results, a process flowsheet incorporating countercurrent water leaching was developed and validated. The optimized proposed two-stage NaOH roasting and water leaching process resulted in over 99 % Li recovery. This direct Li extraction method from α-spodumene offers a sustainable solution, with significant potential to meet the growing demand for lithium while minimizing the environmental footprint of the conventional extraction process.