Bundled capillary chromatography with magnetic field assistance for uranium and lithium extraction from salt lake

Bundled capillary chromatographic columns using methyl vinyl silicone rubber (MVQ) and polytetrafluoroethylene (PTFE) as substrates were constructed and assisted by an axial magnetic field to achieve the coupled extraction of uranium and lithium from a simulated salt-lake environment. Through multiple groups of comparative experiments, the optimal flow rate was identified as 1.81 mL/min, and the optimal magnetic-field-assisted configuration was obtained when the magnetic field direction of the annular magnets was opposite to the solution flow direction (“S–N"). Among the two materials, the MVQ capillary exhibited better separation performance. Without an external magnetic field, the U Li and Mg Li separation factors of the MVQ capillary chromatographic column were 1.32 and 1.008, respectively, and 289 separation stages would theoretically be required to reduce the Mg/Li ratio from 200 to 20. Under the “S-N" magnetic field configuration, the U Li separation factor increased to 1.41 and the Mg Li separation factor increased to 1.015, reducing the theoretically required number of separation stages to 155, corresponding to a 46.4% reduction in the required stage number. Moreover, the action mechanism of the magnetic field was explored, the possible role of the liquid-membrane diffusion model in the separation process was discussed, and the migration behavior of ions inside the capillary chromatographic column was further analyzed. Overall, the application of an external magnetic field enables the in-situ extraction of uranium and lithium in a simulated salt-lake environment, providing a new approach for their separation and enrichment.