Application of microwave radiation for decrepitation of spodumene from the Kolmozerskoe deposit

Abstract

The lithium-ion industry is experiencing a rapidly growing demand for compounds containing lithium. Spodumene is one of the primary industrial minerals used in the production of this metal. It exists in three polymorphic forms. In its natural state, it is known as α-spodumene, which possesses a high resistance to chemical attack due to its compact structure containing silicon and aluminum oxides. When subjected to microwave radiation, α-spodumene undergoes a transformation, first becoming the γ form and then transitioning to the β form. It is known that the β form can be chemically treated to extract lithium. In light of this, microwave exposure was applied to α-spodumene with the aim of decrepitation, followed by sulfuric acid decomposition of the mineral. The mineral was crushed into different sizes (1.0, 0.5, and 0.25 mm). Temperature changes, induced by both conventional and microwave heating, were analyzed. The heating process was continued for samples of various sizes until a temperature of 1200 °C was reached. Sulfation of calcined samples was carried out for 60 minutes at a temperature of 250 °C. After cooling to 22 °C, distilled water was added and mixed for 120 minutes in closed leaching vessels. To determine the recovery of valuable and associated components, leach cakes and the liquid phase were analyzed using inductively coupled plasma atomic emission spectrometry. Based on the analysis of experimental results, the feasibility of using microwave radiation for decrepitation of spodumene to extract lithium is confirmed. The influence of particle size on phase transformations and, consequently, the degree of lithium extraction from spodumene was investigated. It was found that the recovery of lithium during the microwave action and leaching process for particles smaller than 0.25 mm reached 96.82 %. Microwave heating resulted in lower recovery rates of “harmful” components, such as iron, sodium, and calcium, in the leaching process, leading to a higher purity of the resulting product.