Alkaline Process for Extracting Lithium from Spodumene

Abstract

The growing market demand for lithium is mainly due to its use in the manufacture of batteries for electric or hybrid vehicles and portable equipment (cellphones, tablets, power tools, notebooks, etc.). Currently there is great interest in finding new sources of lithium and technologies for itsutilization. Brazil has large lithium pegmatite reserves and spodumene is the most important commercially mined lithium mineral.There are two main routes to obtain lithium carbonate and lithium hydroxide from mineral concentrates. In the first - the acid process - the mineral concentrate is roasted, sulfated with sulfuric acid and leached with water. Soda ash is added to form lithium carbonate. In the second process - the alkaline one - the mineral concentrate is roasted with lime or limestone, forming a clinker which is leached with water, filtered and crystallized as lithium hydroxide monohydrate. In Brazil, only the acidic process is used, although lithium hydroxide is the product most in demand in the domestic market, used mainly by automotive lubricant manufacturers. Lithium hydroxide is the main product in the alkaline process.The processing of spodumene concentrate to produce lithium hydroxide via the alkaline process can provide advantages to the production process, especially by replacing expensive chemicals such as sulfuric acid and soda ash with products such as limestone or hydrated lime, which are produced domestically and have more affordable prices.Thermodynamic modeling using the HSC software 5.1 was conducted to predict different reactions that could occur during roasting of the α-spodumene/CaO system. Lithium extraction from the solid obtained after roasting was also investigated. The results of thermodynamic analysis provided a better understanding of the alkaline process for lithium extraction. The metallurgical tests allowed 84% recovery of the lithium contained in the spodumene concentrate.