Paper Title
Coal Fly Ash: A Waste Created from Thermal Power Plants or a Profuse Source of Rare Earth Elements

Abstract
Coal based thermal power plants are major contributor for electrical power globally and especially in Asian countries. After pulverization, coal is burned in these power plants, which gives rise to a waste material known as coal fly ash. This waste material i.e. coal fly ash is used partially in making construction materials like cement, bricks etc. However,a good amount of coal fly ash is discarded in low lying areas and open mines, posing a serious risk to environmentby contributing to land and water pollution along with human health risks. Over the last few years, it has been established that the coal fly ash is a considerablesecondary source of rare earth elements (REEs), with the REEs being 6-7 times richer in concentration in fly ashes as compared to coal itself. The REEs are crucial pertaining to their uses in clean energy applications such as solar panels, wind turbines, electric vehicles, powerful magnets and other modern sustainable technologies.Several mechanisms of recovery of REEs from coal fly ash has been recognized with acid and alkali leaching being the prominent ones. REEs extracted through these leaching processes vary in concentration depending on the extraction techniques used, type of coal fly ash and the source coal. The review emphasizes that for coal fly ash to be considered as anattractive secondary source of REEs, it needs to be ensured that their maximum utilization is made in variety of applications, which can also help with economic constraints associated with the technology. The review also highlights the need to think forward towards creating commercially feasible extraction methodologies for REEs from coal fly ashes at industrial scales. The same would cater to the increasing demand of REEs for the sustainable energy requirements as well as help in reduction of severe dumping of coal fly ashes in ash ponds and landfills.