Microwave-assisted sample preparation of α-spodumene: A simple procedure for analysis of a complex sample

Abstract

Lithium-ion industry requires high amounts of lithium in high purity and spodumene, together with brine, are the major sources. Spodumene has three polymorphic forms, the one occurring in nature is α-spodumene. This form is highly resistant to chemical attack due to its compact structure containing silicon and aluminium oxides. Chemical analysis of this material is usually performed by combining fusion followed by acid digestion. However, microwave radiation converts α-spodumene to β-spodumene and it is known that this latter form can be chemically attacked using less critical reaction conditions. Based on this behaviour, it was developed a microwave-assisted procedure for chemical analysis of α-spodumene aiming the determination of lithium and other metals of interest by using an acid mixture composed by sulphuric and phosphoric acids and diluted hydrofluoric acid solution. The feasibility of using ammonium fluoride, a less critical reagent, instead of HF was also demonstrated. The heating program was implemented in 60 min at a maximum temperature of 230 °C using closed vessels for digestion of α-spodumene. All elements were determined by inductively coupled plasma optical emission spectrometry.