Structural coordination of rare earth elements on Fe nano-minerals

Rare Earth Elements (RE) are critical raw materials which are essential for modern technologies. The RE concentrations in AMD are significantly high and are retained in the solid precipitated from AMD (i.e., schwertmannite). This study aims to understand how the changes in the physical-chemical parameters in solution affect the retention mechanism of RE in schwertmannite, a poorly crystalline Fe oxyhydroxide sulfate. High affinity between RE and schwertmannite has been described, where RE are retained by double covalent bonding. However, our desorption experiments exhibit a potential single covalent bonding in light RE, together with stronger desorption. We propose a HEXD experiment with RE-enriched schwertmannite experiments to determine how physical-chemical conditions affect the structure in schwertmannite and the bonding with RE. The results will shed light on the effectiveness of the natural attenuation and remediation treatments and the feasibility of extraction of RE from waste.