A novel blended adsorbent granule of crown ether polymer mixed with Mn-based lithium-ion sieves for efficient lithium recycling from shale gas wastewater

The transition in the global energy structure has significantly increased the demand for new energy resources, particularly lithium. To efficiently recover lithium from shale gas wastewater, this study developed an innovative blended adsorbent granule combining crown ether (CE) polymer backbones integrated with Mn-based lithium-ion sieve to maximize lithium adsorption sites. The CE-based adsorbent featured a porous, honeycomb-like interior structure and a high specific surface area of 15.20 m 2 /g, with Mn-based adsorbent uniformly dispersed within the CE polymer matrix. Lithium adsorption performance was systematically evaluated through adsorption isotherms, kinetics, selectivity and reusability tests. The CE-based adsorbent exhibited a lithium adsorption capacity of 17.04 mg/g, recovering over 82.7 % of lithium, with a partition coefficient reaching 1686.75 mL/g, outperforming the PVC-based counterpart. Moreover, the adsorbent showed excellent selectivity for lithium, with a Li/Na separation factor of 421.80. In fixed-bed adsorption-desorption experiments, the CE-based adsorbent processed shale gas wastewater volume up to 100 times its own bed volume, concentrating lithium ions by a factor of 5. To better understand the extraction mechanisms and selectivity, density functional theory calculations were conducted, including optimized structures, molecular orbitals, charge transfer and stabilization energy. Compared to Na + , the CE polymer preferential adsorbed Li + ion, which occupied the crown ether ring core, exhibited shorter O Li bond lengths, greater charge transfer and stabilization energy. This study provides a novel strategy for advancing lithium adsorption materials and presents promising potential for efficient lithium recovery from complex wastewater sources.