Direct extraction of lithium from α-spodumene by alkali mechanochemical conversion and water leaching

Abstract

As a main component in lithium-ion batteries, lithium is crucial for the energy transition. This work investigated the use of mechanochemistry to extract lithium directly from α-spodumene, thus bypassing the energy-intensive stages of decriptation to β-spodumene and roasting. The investigated method is based on mechanochemical milling with sodium hydroxide and water leaching. A full factorial design was implemented to study the effect of milling media size (2–10 mm) and NaOH-ore mass ratio (1.5–8.5) on lithium extraction. ANOVA was conducted to assess the statistical significance of the obtained results. The lithium extraction upon mechanochemical conversion ranged from 20 to 74 %, with the highest extraction observed with 10 mm milling balls and a NaOH-ore ratio of 8.5. XRD results highlighted the disappearance of α-spodumene, with increase in amorphous content and formation of sodium aluminosilicate. FTIR revealed the formation of sodium and lithium carbonates as well as the partial cleavage of the Si-O-Si bonds in α-spodumene. All results suggest that the extraction of lithium from α-spodumene take place upon (i) Li-Na replacement in the mineral structure of α-spodumene and (ii) complete alkali conversion, both resulting in the formation of a water-soluble lithium product.