Study on extraction of rare earth elements from coal fly ash through alkali fusion – Acid leaching

Abstract The growing demand for rare earth elements (REEs), which play vital roles in the production of technologically advanced products, has stimulated the development of original processes to recover REEs from secondary resources. Coal fly ash (CFA), as the main byproduct of coal combustion, enriches REEs in some areas of the world. In this paper, a two-stage hydrometallurgical process (alkali fusion-acid leaching) was developed to recover REEs from CFA. The CFA was firstly roasted at high temperature with Na 2 CO 3 addition, followed by the leaching step. The effects of parameters of the alkali fusion and acid leaching on REEs extraction were investigated. Results indicated that the two-stage method was more efficient compared with direct leaching method. Optimum conditions of alkali fusion were 1:1 (mass ratio of CFA/Na 2 CO 3 ), heating in 860 °C for 0.5 h. The 72.78% leaching REEs efficiency can be obtained in the optimal operation conditions: leaching time (2 h), stirring speed (400 rpm), the HCl concentration (3 mol/L) and the solid-liquid ratio (1/20). This study should be useful in developing a strong theoretical foundation and technological support for the enrichment and extraction of REEs.