Novel approach to recover rare earth metals (REMs) from Indian coal bottom ash

Abstract CSIR-National Metallurgical Laboratory (CSIR-NML), India dealing with coal characterization, has recently made sincere efforts to develop a process to recover REMs from Indian coal bottom ash (CBA) using hydrometallurgical route. The developed process consists of REMs leaching from CBA followed by solvent extraction and selective precipitation. After the selection of suitable leachant, bench scale studies were performed to optimize various process parameters viz. concentration of leachant, mixing time, temperature and pulp density. Maximum dissolution of REMs were achieved using 4 mol/L HCl at 90 °C for 2 h and pulp density 50 g/L. Unused acid present in the leach liquor was further extracted and subsequently processed for selective precipitation of REMs at pH 1.67. A novel process flow-sheet is proposed for the effective recovery of highly pure REMs salt. Developed process at laboratory scale has potential to be commercialized after scale-up and feasibility studies.