Targeting ash generated from coal combustion as secondary source of rare earth elements

The demand of Rare Earth Elements (REEs) has increased for the development of clean and green technologies. Conventional geological sources of REE are insufficient to overcome the high demand of REE; hence, the secondary resources are being actively explored. Coal ashes (CAs), a potentially hazardous material, is one of the best secondary sources containing high concentration of REE. The present study aims to explore the abundance of REE in coal and coal ash from different Thermal Power Stations (TPS). The mineralogy and surface morphology of all samples have been determined. The coals mostly consist of quartz and kaolinite, whereas CAs predominantly contain quartz and mullite. Both coal and CAs are dominated by LREE elements, followed by MREE and HREE. The outlook coefficient (C-out) is close to "1" and the critical percentage (C-p) is more than 30%. Coal ash from some of the TPS is identified as secondary source for REE. Fractionation study of REE from coal to CA is carried out to understand the feasibility of CA. A Pearson correlation has been plotted for individual REE elements with other parameters to understand the affinity of REE to different phases of CA.