Extraction of lithium from lepidolite and spodumene

James Mulwanda

The energy intensive extraction of lithium from α-spodumene (LiAlSi2O6) involves decrepitation at 1100 oC followed by sulphuric acid roasting (200 oC) and water leaching. The extraction of lithium from lepidolite (K(Li,Al)3(Al,Si)4O10(F,OH)2) also involves high temperature (750 – 1000 oC) roasting with additives or direct leaching. The leaching in acid or alkaline media is less attractive due to high reagent consumption and complex purification processes. This thesis reports low temperature extraction of lithium from α-spodumene and lepidolite of 3.58% and 2.37% Li (w/w), from Greenbushes (Western Australia) and Minas Gerais (Brazil), respectively. Characterisation of the solids (feed, calcines, residues, and precipitates) was performed using XRD, SEM-EDS, FTIR and Raman spectroscopy. The ICP-MS analysed the elemental composition of the leach liquors and digested solids. Results from thermogravimetric and differential thermal analysis of feed material and XRD scans of solids were justified by thermodynamic modelling of chemical reactions using HSC software package. The roasting of α-spodumene and lepidolite concentrate of particle size range -75+45 μm with NaOH and Ca(OH)2 for 2 h in a muffle furnace at 500 °C, followed by alkaline leaching at 90 oC, resulted in 98.2% and 98.5% Li extraction, respectively after 3 h, with relatively low dissolution of impurities. Alkaline pressure leaching in autoclave removed about 95% Li, 98% K, 96% Rb and 90% Cs from lepidolite at 250 °C with relatively low NaOH consumption. Alternatively, roasting lepidolite at 500 oC and α-spodumene at 1000 oC with NaHSO4 followed by water leaching yielded 96% and 80% of Li extraction, respectively. Precipitation of Li3PO4 by adding phosphoric acid to the purified alkaline and sulphate leach liquors, both by pH adjustments, recovered 83% and 93% of Li, respectively. Addition of lime to Li3PO4 produced 98% LiOH·H2O with 99.7% conversion.

Extraction of lithium from lepidolite and spodumene

Files and links (1)

Abstract

Details

Metrics