Efficient and selective separation of uranium(VI) from natural waters by MgAl-LDH/CNT composites: Performance evaluation and adsorption mechanism

Uranium (U) contamination in natural waters poses a serious threat to both ecosystems and human health. However, the efficient adsorption and separation of U(VI) remains significantly challenging due to its extremely low concentrations and the complexity of coexisting ions. Herein, we demonstrated that MgAl-LDH/CNT composites with synergistic interfacial properties were successfully synthesized via a hydrothermal method, enabling efficient adsorption and separation of U(VI) from various natural waters while maintaining excellent chemical stability and anti-interference capacity. The evaluation of adsorption performance indicated that U(VI) adsorption by MgAl-LDH/CNT composites reached equilibrium within 10 min at pH 3, exhibiting a maximum adsorption capacity of 126.4 mg/g at 298 K. Furthermore, MgAl-LDH/CNT composites exhibited excellent resistance to coexisting ions, maintaining the adsorption efficiency over 95 % after five adsorption-desorption cycles. The adsorption mechanism studies based on FT-IR, XPS, and DFT revealed that the -OH function groups in MgAl-LDH/CNT composites were involved in U(VI) complexation with a binding energy of 3.69 eV. U(VI) was preferentially enriched on the MgAl-LDH surface and its interface with CNT, confirming the interface-dominated adsorption mechanism of MgAl-LDH/CNT composites. This work provides a promising strategy for efficient adsorption and separation of U(VI) from natural waters, while offering valuable insights into environmental remediation and sustainable nuclear resource management.