Bromide-intercalated poly (triazine imide) as a dual-functional adsorbent for Sr(II) and Co(II) removal from aqueous solution: Contrasting mechanisms of ion exchange and coordination-driven immobilization

Radioactive strontium (Sr 2+ ) and cobalt (Co 2+ ) in nuclear wastewater pose significant environmental risks, leading the need of developing effective remediation strategies. In this study, a poly (triazine imide) (PTI) composite intercalated with bromide (Br − ), referred to as PTI/LiBr, synthesized via a molten salt method, is introduced as a novel adsorbent for the removals of Sr 2+ and Co 2+ . PTI/LiBr composite exhibited rapid adsorption and high efficiency for both radionuclides, driven by electrostatic interactions and partial exchange of Li + ions. The removal efficiency for Sr 2+ and Co 2+ exceeded 95 % within 30 min. Adsorption kinetics followed a pseudo-second-order model, while isotherm analysis indicated that Sr 2+ adsorption aligned with the Freundlich model and Co 2+ adsorption followed the Langmuir model. The adsorption process was confirmed to be spontaneous and endothermic. The γ-radiation tolerance tests verified the structural stability and high adsorption efficiency of the material under ionizing radiation conditions. Additionally, DFT-based wave function and charge density analyses showed a stronger and more stable interaction between PTI/LiBr and Co 2+ compared to Sr 2+ , which might be driven by favorable magnetic interactions and significant charge transfer. This study highlights the potential of PTI/LiBr as a robust and efficient adsorbent for mitigating radioactive pollutants in complex aqueous environments.