Protonated amination magnetic chitosan microspheres for efficient iodide removal from nuclear wastewater: Synthesis,...

A series of novel protonated amination magnetic chitosan microspheres (P-A-MCMs) were successfully prepared for efficient iodide (I^-) removal from nuclear wastewater through the amination and protonation modifications using as-synthesized core-shell-shaped magnetic chitosan microspheres (MCMs) as the matrix materials. The morphology, composition, and surface property of microspheres were fully characterized by various analytical techniques. The characterization results confirmed the successful introduction of protonated amine groups while retaining the good magnetic properties of microspheres. The I^- adsorption mechanism of P-A-MCMs was primarily governed by electrostatic attraction and ion-exchange process. Among the prepared P-A-MCMs, the protonated tetraethylenepentamine magnetic chitosan microspheres (P-TEPA-MCMs) achieved over 89 % iodide removal efficiency across a wide pH range of 3 to 11. The maximum I^- adsorption capacity of P-TEPA-MCMs reached 1.3482 mmol g^-1 within 120 min at 298 K, which was 1.67-fold greater than unmodified MCMs. Thermodynamic and kinetic analyses revealed that the I^- adsorption process of P-A-MCMs was dominated by the monolayer physisorption, following the pseudo-first-order, Langmuir and Dubinin-Radushkevish models. Notably, the P-A-MCMs maintained a high I^- removal efficiency of 88.4 % after ten regeneration cycles, demonstrating excellent reusability. These findings highlight the potential of P-A-MCMs as a cost-effective, high-performance, and recyclable adsorbent for managing radioactive iodide in nuclear wastewater.