HOPO-functionalized MXene self-supporting membrane for highly efficient and selective uranium extraction from radioactive wastewater

The efficient treatment of radioactive uranium-containing wastewater is crucial for environmental safety and sustainable development. Developing high-performance organic-inorganic hybrid materials is recognized as an effective strategy for remediating radioactive wastewater. However, these materials face challenges in solid-liquid separation during practical applications, which significantly restrict their widespread use in uranium extraction from wastewater. To address this, we designed and synthesized a novel self-supporting composite membrane (MXene-AP-HOPO) by covalently conjugating silanized MXene nanosheets (modified with APTES) with carboxylated HOPO monomers via amidation. This design overcomes the limitations of traditional powdered adsorbents, such as difficult solid-liquid separation and propensity for aggregation, thereby providing a reliable material for the rapid and efficient extraction of uranium from aquatic systems.The MXene-AP-HOPO exhibit excellent uranium adsorption capacity (256 mg/g), remarkable adsorption selectivity, favorable antioxidant properties, and good reusability. The adsorption behavior of UO₂ 2+ onto the MXene-AP-HOPO is well-fitted by the Langmuir adsorption isotherm model and pseudo-second-order kinetic model. The detailed adsorption mechanism was systematically investigated using X-ray photoelectron spectroscopy (XPS), extended X-ray absorption fine structure (EXAFS), and density functional theory (DFT) analyses. The results indicate that the efficient adsorption of UO 2 2+ by MXene-AP-HOPO is mainly ascribed to the complexation between UO 2 2+ and the C–OH and C=O groups of HOPO monomers on the membrane surface, together with minor redox effects and electrostatic adsorption from the MXene matrix.This work not only demonstrates a highly promising material for uranium remediation but also provides a general membrane design strategy for advanced environmental applications.