Lithium extraction from β-LiAlSi2O6 using Na2CO3 through thermal reaction

Abstract

• Heating of β-spodumene (mineral and synthetic) and sodium carbonate was studied. • NaAlSi 2 O 6 is produced by Li + substitution in β-spodumene after heating at 400 °C. • At high temperature (above 600 °C) NaAlSiO 4 is obtained. • Li 2 CO 3 is recovered from a mixture containing NaAlSi 2 O 6 with a yield of 70%. • β-spodumene displays similar thermal behavior regardless its origin. The aim of this study is to evaluate the role of Na 2 CO 3 in solid-state lithium extraction from β -spodumene (β -LiAlSi 2 O 6 ) under both dynamical and static heating conditions. Different samples of β -spodumene were used: one obtained from a mineral sample and another synthesized from oxides/carbonates reagents. Structural, chemical, microstructural and thermal analysis techniques were employed to analyze the samples before and after reaction. Experimental results show that lithium could be extracted from β -spodumene structure through sodium aluminosilicate phases formation under air atmosphere: NaAlSi 2 O 6 at low temperature (∼400 °C) and NaAlSiO 4 at high temperature (above 600 °C). The comparison between both β -spodumene samples reveals the formation of the same crystalline phases under both dynamical and static heating conditions, although mixtures of Na 2 CO 3 with synthetic β -spodumene show minor reactivity at low temperature. In addition, the study of different molar ratios of LiAlSi 2 O 6 :Na 2 CO 3 evidences that a major amount of NaAlSi 2 O 6 phase is obtained at 400 °C for the 2:1 mol ratio. Lithium can be recovered by additional dissolution and drying stages in the form of lithium carbonate Li 2 CO 3 reaching a high yield. These results are in agreement with thermodynamical calculations obtained for the LiAlSi 2 O 6 -Na 2 CO 3 system.