Relationship Between the Carbon Chain Structures of Amide Podand Derivatives and Adsorption Performance for Europium

Radioactive wastewater containing high concentrations of radionuclides threatens ecosystems and human health. Developing environmentally friendly adsorbents with high enrichment efficiency and ease of solid–liquid separation is essential for removing europium from wastewater. In this study, three amide podand derivatives with different alkyl chain structures were loaded onto polyacrylonitrile via electrospinning, yielding DODGA@PAN, DPDGA@PAN, and DEHDGA@PAN nanofibers. The presence of two carbonyl oxygens and one ether oxygen in these materials enhances coordination with trivalent metal ions, making them highly efficient in europium removal.In reuse tests, DODGA@PAN and DPDGA@PAN maintained strong performance, with only 3.84% and 3.87% decreases after five adsorption–desorption cycles, respectively. In contrast, DEHDGA@PAN, due to its branched structure, exhibited higher adsorption capacity but lower reusability. This branched structure increased porosity, improving adsorption while also causing deformation, reducing its durability. Europium removal efficiency varied with changes in pH, temperature, time, and initial concentration. The Langmuir isotherm model confirmed effective europium adsorption by all three nanofibers. Kinetics indicated chemisorption, while thermodynamics showed the process was endothermic and spontaneous.