Sulfomethylated lignin-intercalated layered double hydroxide nanosheets for high-efficiency uranium extraction from seawater

The efficient extraction of uranium from seawater remains a significant challenge in nuclear resource recovery. Herein, we report a special nickel-cobalt layered double hydroxide (Ni Co LDH) intercalated with sulfomethylated lignin (SL) via co-precipitation (denoted as Ni-Co@SLx). The SL intercalation accomplishes dual optimization at both structural and functional levels. The sulfomethyl groups on the SL molecular chains expose a plethora of negatively-charged sites within the interlayers, which offer additional sites for electrostatic adsorption and coordination anchoring. Meanwhile, the introduction of SL substantially increases the specific surface area, enabling Ni-Co@SL2 to achieve a 1.51-fold uranium adsorption capacity in comparison to the pristine Ni Co LDH. The optimized Ni-Co@SL2 composite exhibits an exceptional U(VI) adsorption capacity of 298.95 mg g −1 , outperforming most reported LDH-based adsorbents, while maintaining >80 % capacity retention after 5 regeneration cycles. Practical evaluation using natural seawater (Bohai Sea, China, 38.96°N, 121.62°E) reveals its industrial potential, achieving 6.77 mg g −1  U(VI) adsorption within 24 h and reaching 11.33 mg g −1 after 27 days in 500 L seawater. Mechanistic studies indicate that uranium adsorption occurs primarily through electrostatic interaction and chemical adsorption. This study pioneers the strategic integration of functionalized lignin with LDH materials, establishing a sustainable platform for seawater uranium extraction.