Non-hydrothermal synthesis of robust and radiation-resistant sodalite microspheres for effective removal and in-situ immobilization of Cs⁺ and Sr²⁺

The safe management of radioactive ¹³⁷Cs and ⁹⁰Sr from nuclear wastewater requires not only efficient capture but also permanent immobilization, yet current strategies often treat these as separate processes, leading to incompatibility and complex operations. Herein, non-hydrothermal method based on geopolymer technology was developed to fabricate robust sodalite zeolite microspheres (GXU-SODs) for the integrated adsorption-immobilization of Cs⁺ and Sr²⁺. The synthesized GXU-SODs exhibited well-defined crystalline structure and spherical morphology with compressive strength of 13.88 MPa. Batch adsorption experiments revealed the maximum adsorption capacities (Q_m) of GXU-SODs were 56.67 and 59.64 mg·g^-1 for Sr²⁺ and Cs⁺ with rapid kinetics of 1.21 and 0.94 g·mg^-1·min^-1, respectively. The adsorption process followed pseudo-second order and Langmuir models, indicating monolayer homogeneous chemisorption. Meanwhile, GXU-SODs exhibited excellent radiation resistance, retaining >96 % structural integrity and adsorption performance after 500 kGy. Dynamic adsorption column tests confirmed excellent breakthrough performance and practical applicability in real seawater. The adsorbed GXU-SODs could permanently immobilize radionuclides via simple thermal treatment at 1100 ºC without secondary additives, achieving 28-day leaching rates significantly below regulatory standard. Combining XRD, XPS, FT-IR, SEM-EDS and DFT calculations revealed the ion exchange, chemisorption and lattice incorporation within the sodalite cages were the primary mechanisms for the effective adsorption and long-term immobilization of Sr²⁺ and Cs⁺. This work presents a novel, scalable, and energy-efficient synthesis route for advanced sodalite-based materials and establishes an integrated adsorption-immobilization strategy for the treatment and safe disposal of radioactive wastes.