Production of Lithium - A Literature Review Part 1: Pretreatment of Spodumene

Among lithium minerals, spodumene contains the highest value of lithium, and therefore developing new or improving existing processes for extracting lithium from spodumene can have a significant effect in lowering the cost of lithium production. Spodumene can exist in three different polymorphs, namely alpha-, beta-, and gamma-spodumene. Studies to date confirm that alpha-spodumene, which is the naturally occurring form of spodumene, is refractory to leaching and has to be converted to a more reactive form in which lithium atoms are more accessible to the extraction reagent. So far, calcination at temperatures of around 1000 degrees C prior to extraction is the most promising approach. The calcination produces beta-spodumene as the primary polymorph and in some cases limited amounts of gamma-spodumene. In addition to calcination, microwave-assisted heating and mechanical activation can also produce phases that are more reactive. Microwave-assisted production of beta-spodumene can be achieved faster and using less energy than heating in a conventional oven. However, some challenges with this approach have been identified. Mechanical assisted processes too can lead to the formation of an amorphous phase, which is to some extent suitable for efficient lithium extraction. This article will provide details of spodumene mineralogy, an overview of current pretreatment technology, and a summary of alternative options for the activation stage of the extraction process.