Performance and characterization of nano-engineered silica waste concrete composite for efficient marine radionuclides remediation

The disposal of solid and radioactive waste poses significant risks to terrestrial and marine ecosystems. This study presents a sustainable solution by recycling silica-rich glass waste (RG) and fly ash (FA) to develop a functional nanocomposite concrete for radionuclide treatment. A Radionuclide removal Zeolite (RrZ) was hydrothermally synthesized from RG powder at low temperature and NaOH molar ratio. The RrZ was incorporated into a porous geopolymer composite concrete (PGCC) comprising 20 % RrZ and 80 % FA, with SiO₂/Na₂O = 1, liquid-to-solid ratio (L/S) = 0.33, paste-to-bone ratio (B/A) varying from 0.15 to 0.2, and porosity (P) from 14.95 to 25.45 %. The results from SEM, TEM and BET indicated a highly porous structure of RrZ adsorbent with mesopores capable of achieving high adsorption efficiency (83.13–97.71 % for Sr²⁺ and 55.31–91.01 % for Cs⁺) within short time, adhering to the quasi-second-order kinetic models. Moreover, the XRD results identified key crystalline phase of analcime (NaAlSi₂O₆•H₂O), and no new phase formed after ion exchange with Sr²⁺ and Cs⁺, while the FTIR analysis revealed minimal chemical changes post-adsorption. Additionally, the porosity of 14.95 %–25.45 % and water permeability of 1.876–11.956 mm/s were the key factors for PGCC design, while larger aggregates and lower B/A ratios helped to optimize the adsorption. The ANOVA analysis revealed that aggregate size was the most significant factor for single-cycle adsorption, followed by porosity and B/A ratio. This study demonstrates that PGCC effectively combines waste recycling with environmental remediation, offering a durable and efficient method for hazardous radionuclide removal from marine ecosystems.