Geochemical Characterization and Process Response of Coal-Derived Post-Mining Waste to Dry Electrostatic and Magnetic Separation: Implications for REE Pre-Concentration Screening

This study compares the response of five coal-derived post-mining waste streams from Poland and the Czech Republic to dry electrostatic and magnetic separation, with emphasis on rare earth element (REE) enrichment, product yield, and material variability. The materials included dump-derived wastes and process-derived streams from beneficiation operations. Electrostatic separation was performed on the <45 µm fraction, whereas magnetic separation was performed on the <3 mm fraction. Chemical composition was determined by ICP–MS, and process response was evaluated using enrichment factor (EF), product yield, and mass distribution. The ΣREE content of the feeds ranged from 109.33 to 250.54 ppm, while loss on ignition varied from 12.5% to 50.8%, confirming substantial heterogeneity. Electrostatic separation produced only moderate and material-specific enrichment, with EF ΣREE values generally close to unity and reaching a maximum of 1.26 for the Haldex K conductive product. Magnetic separation was less favourable, as most magnetic products showed ΣREE depletion or very low yields. Although the Haldex K paramagnetic product reached EF ΣREE = 1.30, its yield was only 0.2%. Overall, no tested configuration combined high REE enrichment with high product yield, indicating limited standalone beneficiation potential for the investigated materials. This study provides a comparative process-response assessment of low-grade, heterogeneous coal-derived post-mining waste streams and shows that dry electrostatic and magnetic separation can reveal material-dependent REE partitioning behaviour under laboratory conditions.