Characterization study of rare earths, yttrium, and scandium from various Colombian coal samples and non-coal lithologies

Abstract

This study provides data on the occurrence and distribution of rare earth elements, yttrium, and scandium (REY + Sc) in coals and non-coal lithologies associated with coals from various Colombian coalfields. A number of authors have characterized the REY + Sc content of various international coal deposits; however, no study to date has specifically addressed the REY + Sc content of Colombian coals, despite Colombia's prominence as a global coal producer. In this study, 24 samples were collected from seven coalfields and subjected to REY + Sc analysis, density fractionation, and modified release tests. Overall, the Colombian coals analyzed in this study have an average REY + Sc abundance of 45 ppm on a dry whole coal basis (459 ppm on a dry ash basis) whereas the non-coal lithologies have an average REY + Sc content of 222 ppm. In particular, materials collected from the Antioquia-Viejo Caldas coalfield were found to contain a relatively higher amount of REY + Sc (>100 ppm) relative to the rest of the samples, which may be attributed to the volcaniclastic character of the sediment associated with the seams. Moreover, test results from the density fractionation and modified release tests show that the inorganic constituents are the major hosts of REY + Sc in Colombian coals, which is reflected by a strong and positive linear relationship existing between REY + Sc and sample ash yields.