Retention mechanism of rare earth elements on Fe nanominerals

Rare Earth Elements (RE) are critical raw materials which are essential for modern technologies. The RE concentration in AMD is significantly high, and RE are retained in the solids that precipitated in AMD (i.e., schwertmannite). This study aims to understand how the changes in the physical-chemical parameters in solution affect the retention mechanism between RE and schwertmannite, the poorly crystalline Fe oxyhydroxide sulfate. High affinity between RE and schwertmannite has been described, where RE are retained in the solid structure by double covalent bonding. However, our recently performed desorption experiments exhibit a potential single covalent bonding in light RE. We propose La L3-edge and Gd L3-edge HERFD EXAFS experiments on RE-enriched schwertmannite to determine how physical-chemical conditions affect the RE retention. The results will shed light in the effectiveness of contaminant attenuation process and the feasibility of extraction of RE from schwertmannite.