Formation of pseudo-crown ether sites in chitosan aerogel via ion-imprinting for selective and acid-stable Sr2+ capture

Selective removal of 90 Sr from highly acidic nuclear wastewater remains challenging due to strong H + competition and poor adsorbent stability. Here, we report a Sr 2+ -imprinted chitosan aerogel (IIP-CE-CS) with pseudo-crown ether recognition cavities, synthesized via ion-imprinting combined with low-temperature thermally induced phase separation. The material exhibits a high specific surface area (142.5 m 2  g −1 ) and a hierarchical porous structure (pore volume 0.90 cm 3  g −1 ). At pH = 1.0, IIP-CE-CS achieves a Sr 2+ adsorption capacity of 142.6 mg g −1 , fast pseudo-second-order kinetics, and excellent selectivity over competing ions (α(Sr/pb) = 2.74). The imprinted cavities retain their configuration after acid elution, resulting in 82% capacity retention over five adsorption–desorption cycles. Mechanistic studies confirm that Sr 2+ capture occurs via specific coordination with ether‑oxygen atoms within the imprinted cavities, while protonated amino groups stabilize the aerogel structure under acidic conditions. This work provides a regenerable and highly selective adsorbent for Sr 2+ separation from acidic solutions