Crown-position recognition-driven selective adsorption: Efficient capture of strontium and cesium ions by dual crown ether-modified chitosan

A novel chitosan (CTS) - based composite material, CTS/B18C6/B21C7, has been developed through the Schiff base reaction, incorporating two distinct crown ether ligands - aldehyde-benzo-18-crown-6 (B18C6) and aldehyde-benzo-21-crown-7 (B21C7). This design enables efficient and selective adsorption of cesium and strontium. The material features two recognition sites of exclusive affinity, enhancing selective adsorption through the matching cavity sizes of the crown ethers with Sr 2+ and Cs + . The structure and surface properties were characterized using SEM, TG, FT-IR and XPS confirming the successful Schiff base reaction and effective material synthesis. Adsorption experiments revealed that CTS/B18C6/B21C7 exhibited strong affinity and high adsorption capacity for Sr 2+ and Cs + . Under strong acid conditions (pH < 1), the adsorption strength increased, and higher acidity further enhanced adsorption capacity, indicating that electrostatic and other interactions play significant roles in the adsorption process. The Sips isothermal model was more suitable for describing this adsorption process, with maximum adsorption capacities of 172.11 mg/g for Cs + and 132.23 mg/g for Sr 2+ determined. These findings highlight the potential application of CTS/B18C6/B21C7 in treating radioactive nuclides.