Lithium in Greek Coal Fly Ashes: Contents and Characterization by Sequential Extraction

Lithium belongs to the critical elements and is used in a variety of high-tech applications. In the context of the circular economy, demand has arisen for technologies that are able to recover high-tech metals from wastes and byproducts. To achieve efficient recovery, apart from assessing metal enrichment, extensive knowledge of metal binding and leaching characteristics is required. The aim of the present study is to investigate the Li contents and mode of occurrence in Greek coal fly ashes. Eight coal fly ashes from different power plants in Greece were collected, and their major constituents were analyzed by X-ray fluorescence spectroscopy (XRF); their mineralogy was studied by X-ray powder diffraction (XRD), and their Li content was determined by ICP–MS. To identify Li binding and leaching characteristics, two sequential extraction methods (Tessier and BCR) were employed. The results showed that the Li content in the samples studied was between 95 and 256 μg/g and could be mainly attributed to the amorphous material encountered in the samples. The sequential extraction experiments revealed that 70–90% of Li is included in the residual fraction, indicating that it is strongly bound to the fly ash matrix.