Synergistic regulation of crystal structure and surface properties by cerium doping: enhancing lithium extraction...

Titanium-based lithium-ion sieves (HTOs) have shown significant potential for lithium extraction from brines. However, their industrial application is severely constrained by a relatively low practical adsorption capacity and structural instability arising from metal dissolution during repeated cycling. To address these issues, large-radius cerium(Ce) was incorporated into the framework of a layered titanium-based lithium-ion sieve precursor (LTO) via a high-temperature solid-state method. This strategy achieved moderate unit cell expansion, optimization of the pore structure, and synergistic regulation of surface charge properties. Microscopic characterization and adsorption kinetics revealed that Ce doping not only widened the Li⁺ diffusion channels and reduced mass transfer resistance, but also increased the specific surface area and enhanced surface electronegativity, providing more active sites and a favorable interfacial exchange environment for Li⁺. In a simulated solution with an initial Li⁺ concentration of 100 mg L^-1, the equilibrium adsorption capacity of HTO-Ce-1% reached 36.89 mg g^-1, representing a 25.3% increase compared to pristine HTO. Furthermore, this modified material exhibited favorable Li⁺ sieve selectivity in simulated brines containing multiple coexisting ions. Benefiting from the improved cyclic stability conferred by Ce doping, HTO-Ce-1% suppressed the dissolution loss of Ti⁴⁺ after ten adsorption-desorption cycles, exhibiting an average dissolution rate of 0.667% and maintaining a capacity retention of 90.44%. These findings suggest that the Ce-doped lithium-ion sieve holds certain promise for the extraction and recovery of lithium from lithium-bearing brines.