Selective adsorption performance and mechanism of ZIF-8-functionalized titanium-based lithium-ion sieve/cellulose composite aerogel for lithium recovery from salt-lake brine

ZIF-8 improves HTO dispersion and ion transport within the cellulose aerogel. • ZIF-8/HTO@CA achieves 29.85 mg/g Li + uptake and 58.62% brine extraction. • Li + selectivity is governed by HTO recognition, dehydration, and lattice migration. Selective lithium recovery from high-Mg/Li salt-lake brines remains challenging because of competing ions and slow ion transport. In this study, a ZIF-8-functionalized H 2 TiO 3 (HTO)/cellulose composite aerogel (ZIF-8/HTO@CA) was prepared for Li + adsorption. The cellulose aerogel provided a three-dimensional support for particle immobilization and recovery. ZIF-8 improved HTO dispersion and provided additional transport interfaces. The composite had a specific surface area of 117.89 m 2 ·g −1 and retained a mesoporous structure. Its Li + adsorption capacity reached 29.85 mg·g −1 at pH 11 and 298 K. Nonlinear isotherm fitting showed that the Langmuir model gave a better description of the equilibrium data, with a fitted maximum capacity of 34.53 mg·g −1 . Both pseudo-first-order and pseudo-second-order models reasonably described the adsorption kinetics. Competitive adsorption tests showed preferential Li + uptake over Na + , K + , Mg 2+ , and Ca 2+ . The Li + /Mg 2+ separation factor increased from 46.29 for pristine HTO to 80.33 for ZIF-8/HTO@CA. In natural salt-lake brine with an initial Mg/Li mass ratio of 706, the composite achieved a single-stage Li + extraction efficiency of 58.62% without additional pH adjustment. The adsorption efficiency was 77.34% after the sixth adsorption–desorption cycle. Zeta-potential measurements and DFT calculations suggest that Li + selectivity mainly originates from the intrinsic recognition of HTO and the combined effects of ion dehydration and lattice migration. ZIF-8 mainly improves particle dispersion, accessible interfaces, and ion transport. These results demonstrate the potential of ZIF-8/HTO@CA for lithium recovery from complex brines.