Novel polyelectrolyte functionalized mesoporous silica for sustainable and ultraselective adsorption of Re(VII) and 99Tc(VII) remediation.

The selective recovery of perrhenate (ReO4-) and radio-toxic pertechnetate (99TcO4-) from complex and hypersaline matrices remain challenging task for nuclear waste management and strategic metal valorization. High-performance novel anionic sorbent (QA-APMA-Si), is engineered by anchoring high-density cationic poly-additives, covalently bonded onto a mesoporous silica via surface-initiated redox polymerization. The resulting material features with superior capacity and selectivity toward Re and 99Tc. Adsorption experiments show high sorption efficiency. The kinetic data fitted well to the PFORE (< 30 min for total sorption). Meanwhile, sorption isotherms confirm an endothermic entropy-driven process evidenced by the twofold enhancement in adsorption capacity (1.35 mmol/g at 21 ℃ to 2.61 mmol/g at 50 ℃). Crucially, QA-APMA-Si demonstrates extraordinary salinity tolerance maintaining high capture efficiency even in hypersaline media (20% NaCl and NaNO3) with a limited sorption loss (< 15%). The selectivity coefficients (SFRe/Metal) exceeding 140-fold at pH 2.1 over competing ions. Furthermore, direct 99TcO4- hot tests confirmed rapid capture, with 99.98% and 99.51% for 50 and 102 Bq/L, respectively. The residual activity was reduced to near-background levels with loading capacity 4434 Bq/g. The optimum sorbent dose (SD) required for complete removal of radionuclide element (supporting zero-waste remediation) was determined to be 1.05 g/L. Different mechanisms pathways are anticipated including anion-exchange and dipole-anion stabilization. A nearly complete regeneration efficiency is maintained over 10 cycles with negligible Si leaching detection, attributed to the robustness of its covalent grafting. This sorbent architecture minimizes steric hindrance and leverages carboxylic and amide functionalities to create multiple binding pathways. The design achieves high sorption capacity, selectivity, rapid mass transfer, and regenerability, and with validated to both ReO₄⁻ and ⁹⁹TcO₄⁻. Confirming its sustainability for efficient Re/99Tc remediation in industrial and nuclear fuel cycle waste.