Investigation of the Processes of Rare Earth Elements Extraction from Decomposition Products of Primorskaya Thermal Power Plant’s Ash and Slag Wastes

Ash and slag waste (ASW) from coal combustion is a potential source of many valuable components, while their processing also solves an important environmental problem. This study assessed the possibility of extracting valuable components, mainly rare earth elements (REE), from the ASW of the Primorskaya thermal power plant (TPP), Primorsky Krai, Russia. Processes of REE extraction using n-tributyl phosphate from liquid ASW decomposition products have been studied. A significant dependence of the extraction degree on the method of ash leaching, the acidity of the environment, and the content of matrix components is shown. For nitric acid solutions, the degree of extraction of most rare earth elements was more than 90% and their subsequent re-extraction into the aqueous layer exceeded 85%. Fractions of silicon, aluminum, and iron oxides with a total mass of more than 75% of the ASW initial mass were obtained as additional valuable products.