Morphological Distribution and Phase Composition of Rare Earth Elements in Waste Incineration Fly Ash

Abstract

Utilising scanning electron microscopy (SEM) and X-ray powder diffraction (XRD), the morphological and phase composition characteristics of waste incineration fly ash were meticulously analysed. Morphological evaluations revealed a predominant presence of irregularly shaped particles, encountering a spectrum of structures inclusive of polycrystalline polymers and amorphous forms. Additional particle shapes encompassed polygons, strips, blocks, and flakes, while a notable high porosity between particles and a markedly rough surface were observed. Despite the scarcity of complete crystals within the ash, the majority manifested as polycrystalline polymers and amorphous forms, indicating the structural complexity intrinsic to waste incineration fly ash. Through the deployment of chemical continuous extraction technology, forms, migrations, and transformation laws pertaining to rare earth elements (REEs) in fly ash were elucidated. In three fly ash samples analysed for REEs, the most abundant state was identified as the residual, succeeded by the Fe-Mn oxide-bound state and minimally, the carbonate-bound state. Amongst all REEs, Ce exhibited the highest prevalence, followed by La, Y, Nd, Gd, and other elements. Furthermore, the source of waste and the respective incineration process markedly influenced REEs content.