Synthesis and performance evaluation of bentonite co-doped with sulfur and bromine for selective radionuclide sequestration from aqueous environments

This study investigates the synthesis and application of bentonite co-doped with sulfur and bromine (S/Br-B-2.0) as a novel, scalable adsorbent for the selective removal of ⁶⁰Co and ^85,90Sr, which are significant contaminants in liquid radioactive waste, with the aim of overcoming the limitations of conventional treatment methods. The material was synthesized by a hydrothermal method and characterized by XRD, FE-SEM, BET, FTIR, XPS, and zeta potential analysis. The adsorption kinetics revealed different mechanisms: ⁶⁰Co followed a pseudo-second-order model, suggesting chemisorption, while ^85,90Sr followed a Elovich model, applied to heterogeneous surfaces, highlighting variations in surface activity and activation energy. Isothermal studies showed that ⁶⁰Co adsorption followed the Freundlich model, indicating multilayer adsorption with a maximum capacity of 46.66 mg/g, while ^85,90Sr followed the Langmuir model, indicating monolayer adsorption with a capacity of 43.20 mg/g. Batch experiments confirmed consistent performance over pH, temperature, and dosage variations. Reusability tests showed moderate retention of adsorption capacity after five cycles, proving the durability of the material. Response surface methodology optimized the adsorption process by analyzing the effects of pH, temperature, concentration, and contact time. The results highlight the potential of S/Br-B-2.0 as an efficient and sustainable solution for radionuclide removal, particularly for managing liquid radioactive waste in water treatment and environmental remediation.