QUANTITATIVE VISUALIZATION OF COMPLEX MINERAL DECOMPOSITION PROCESSES: A STRATEGY TO IDENTIFY NOVEL ENERGY-EFFICIENT APPROACHES FOR THE RECOVERY OF LITHIUM FROM LCT PEGMATITES

As long as Li-ion batteries remain the dominant technology for transport electrification, the demand for lithium will grow dramatically (estimated 30 to 40 times by 2040). Consequently, a sustainable battery supply chain requires diversified sources of lithium and innovative recovery approaches to produce high-purity cathode precursors (e.g. Li₂CO₃, LiOH∙H₂O) economically. In this context, considering the many occurrences of LCT pegmatites in the Superior geological province within Canada, there is significant interest in accessing lithium from these deposits. However, due to the refractory nature of a-spodumene and petalite, conventional recovery processes are very energy-intensive, involving an initial high-temperature treatment (>1000^oC) to induce a transition to a b-spodumene solid solution, a reactive phase that can be decomposed in a subsequent hydrometallurgical stage. In this context, an extensive study focusing on the investigation of alternative energy-efficient strategies to directly decompose the primary lithium aluminosilicates hosted in LCT pegmatites at low temperatures was initiated.

Here we report advancements in the quantitative visualization of complex reactive processes involved when a starting material with textural and modal properties consistent with the conversion of petalite to SQI (spodumene quartz intergrowth) is exposed to concentrated alkali media at temperatures below 500^oC, followed by a water leach to recover lithium in solution. This was achieved by adopting a correlative characterization approach including automated quantitative mineralogy, electron probe X-ray microanalysis, laser ablation inductively coupled plasma mass spectrometry, electron backscatter diffraction, and Raman confocal microscopy, as well as sample preservation techniques allowing access to highly soluble phases. We will discuss how this can provide a clear picture of factors that promote efficient alkali exchange leading to optimal energy-efficient pathways for the direct decomposition of a-spodumene with strong partitioning of lithium in solution.