LAUSR

Abstract Coal ash is considered as a promising alternative resource for rare earth elements and yttrium (REE + Y or REY) recovery. Coal ash samples (fly ash and bottom ash), as well as corresponding feed coals, collected from the Luzhou coal-fired power plant in Sichuan, southwestern China were analyzed for their chemical and mineralogical characteristics. The fly ash was further tested for its feasibility of REE extraction. The feed coals are characterized as a low-volatile bituminous, medium‑sulfur, and high-ash coal, sourced from the Guxu coalfield (Late Permian Longtan Formation) in Sichuan, SW China. REE and Y, along with high-field-strength elements Zr(Hf) and Nb(Ta), and Li, F, Sc, V, Cr, Co, Cu, Zn, Ga, Ge, Se, Sr, Cd, In, Sn, Hg, Th, U, are all enriched in the feed coal. The mineralogical compositions of the feed coals are dominated by kaolinite and illite/smectite (I/S) mixed layers, followed by the carbonate minerals including calcite, siderite, ankerite, and minor amounts of anatase and jarosite. The combustion of the feed coals produces a Class F fly ash, characterized by an aluminosilicate composition with a low CaO content. The bottom ash is compositionally similar to the fly ash, except that it is more enriched in high-density elements (Fe and Mn), and more depleted in volatile elements. REY are enriched in both the fly ash and bottom ash, although heavy REY (HREY) are notably more enriched in the fly ash. Mineralogical analysis shows that the fly ash consists of >70% amorphous glass and