Obtaining Li2CO3 from β-LiAlSi2O6 by solid state reaction with NaOH

Abstract

Li2CO3 was obtained by the solid-state reaction between β-LiAlSi2O6 (β-spodumene) and NaOH under dynamic and static thermal conditions in the temperature range between 300 °C and 800 °C followed by washing and drying stages. Prior to the reaction, the reagents have been mixed by mechanical milling 1 h under air atmosphere at room temperature. The ball-milled mixture of β-LiAlSi2O6:NaOH has been studied after heating to determine its morphological, microstructural, structural and thermal stability characteristics. The results indicate that sodium from NaOH replaces lithium in the aluminosilicate structure by heating under air. Different crystalline phases have been observed depending on temperature: NaAlSi2O6 near 300 °C and non-stoichiometric sodium aluminosilicates over 500 °C. The only lithium-containing product formed has been Li2CO3 obtained at 350 °C and 300 °C under dynamic and static heating conditions, respectively. Additional experiments at different β-LiAlSi2O6:NaOH molar ratios have shown that a major amount of NaAlSi2O6 phase is obtained for the 1:1 M ratio. Lithium recovery experiments (as Li2CO3) combining washing and drying stages have given 91.2 wt% of Li2CO3 in the recovered solid residue.