Extraction of Lithium and Synthesis of Kaolinite from α‐Spodumene via Alkali Calcination

Abstract

AbstractExtracting lithium from spodumene by sulfuric acid roasting is the largest commercialized way at present, which not only consumes a large amount of energy but also produces massive waste residue that will cause environmental problems. In this work, a new process for extracting lithium by directly decomposing α‐spodumene through alkali calcination is designed. The reaction of α‐spodumene with Na2CO3 at 750 °C for 2 h can decompose it and form nepheline and lithium silicate/sodium silicate. The nepheline and soluble lithium silicate/sodium silicate are separated by water leaching, and 93.9 % of lithium can be leached under optimal conditions. In addition, the synthesis of nano‐kaolinite is investigated with nitric acid solutions. Conversions of 98.7 % were obtained with 0.4 M nitric acid at 250 °C and an L/S ratio of 17.5 L/kg. The water leachate can precipitate Li2CO3 with a purity of 99.0 % by CO2 after desilicated by CaO. The final yields of Li2CO3 and kaolinite relative to the Li and Si content of the starting minerals are 91.4 % and 48.5 %, respectively. This new method achieves the full utilization of spodumene with lower energy consumption and demonstrates great potential for industrial applications.