Rare Earth Element Occurrence and Leaching Behavior in Stone Coal Based on Synchrotron-Based Elemental Analysis

Stone coal is an important vanadium-bearing resource and a potential source of rare earth elements (REEs). Previous studies have mainly focused on the bulk occurrence, resource potential, and leaching behavior of V or REEs in stone coal, whereas the microscale spatial relationships between V and REEs and their evolution during leaching remain poorly constrained. In this study, three representative stone coal samples were analyzed by synchrotron radiation micro-X-ray fluorescence (μXRF) to characterize the microscale distributions of V and REEs in raw samples and corresponding leaching residues. Pearson correlation analysis was further used to quantify changes in V–REE spatial relationships during leaching. The results showed that V–REE relationships were generally weak and were modified to different extents after leaching. In the GZ sample, the V–Eu correlation coefficient decreased from 0.63 to 0.34, indicating that the migration of V and REEs was not fully synchronized. The three samples also showed different REE distribution tendencies after leaching: GZ showed partial transfer of REEs to the leachate with residual retention, PX showed mixed behavior with appreciable retention in the residue, whereas PZ retained REEs predominantly in the residue. These results suggest that the integrated utilization of V and REEs in stone coal can be better achieved through a staged recovery route, in which the REE recovery pathway is determined according to their actual distribution between the leachate and the residue after V leaching. This study provides a microscale basis for the comprehensive utilization of coal-related critical metal resources.