Nanocrystalline Silicotitanate for Selective Lithium Adsorption from Industrial Lithium Sludge Leachates

The rapid expansion of the lithium-ion battery industry has led to the generation of substantial amounts of lithium sludge, representing a largely untapped yet promising secondary lithium resource. Acid leaching of this sludge produces a lithium-rich leachate with high concentrations of coexisting impurities, such as Fe3+ and Al3+, posing significant challenges for selective lithium recovery. In this study, crystalline silicotitanate (CST) was employed as an adsorbent to selectively capture Li+ from complex leachates, leveraging its unique molecular sieve framework and ion-exchange properties. CST exhibited a Li+ adsorption capacity of 16.26 mg/g and a removal efficiency of 73.91% within 4 h, while maintaining high selectivity toward Li+ under the investigated conditions. After desorption, CST retained its original microstructure and morphology. Theoretical analysis indicates that Li adsorption is a spontaneous process, with Ti–O sites representing the most stable adsorption locations. The small ionic radius of Li+ allows it to match the channel size within the CST framework and spontaneously replace Na+ at the framework sites, thereby conferring preferential selectivity toward Li+. These findings not only advance the sustainable recovery of secondary lithium resources from lithium sludge, but also provide theoretical support and practical guidance for the broader application of CST in lithium recovery.