Sulfur vacancy-rich bismuth sulfide nanowire derived from CAU-17 for radioactive iodine capture in complex environments: Performance and intrinsic mechanisms

Effective capture and immobilization of volatile radioiodine from the off-gas of post-treatment plants is crucial for nuclear safety and public health, considering its long half-life, high toxicity, and environmental mobility. Herein, sulfur vacancy-rich Vs-Bi2S3@C nanocomposites were systematically synthesized via a one-step solvothermal vulcanization of CAU-17 precursor. Batch adsorption experiments demonstrated that the as-synthesized materials exhibited superior iodine adsorption capacity (1505.8 mg g-1 at 200 °C), fast equilibrium time (60 min), and high chemisorption ratio (91.7%), which might benefit from the nanowire structure and abundant sulfur vacancies of Bi2S3. Furthermore, Vs-Bi2S3@C composites exhibited excellent iodine capture performance in complex environments (high temperatures, high humidity and radiation exposure). Mechanistic investigations revealed that the I2 capture by fabricated materials primarily involved the chemical adsorption between Bi2S3 and I2 to form BiI3, and the interaction of I2 with electrons provided by sulfur vacancies to form polyiodide anions (I3-). The post-adsorbed iodine samples were successfully immobilized into commercial glass fractions in a stable form (BixOyI), exhibiting a normalized iodine leaching rate of 3.81×10-5 g m-2 d-1. Overall, our work offers a novel strategy for the design of adsorbent materials tailed for efficient capture and immobilization of volatile radioiodine. Due to the biological toxicity, ionizing radiation and environmental mobility, volatile radioiodine will affect the ecological environment and human health. Bi-based adsorbents have become potential candidates for their low-cost and high adsorption properties. This work proposed a solvent thermal vulcanization method to obtain Vs-Bi2S3@C nanocomposites with abundant sulfur vacancies. Importantly, the prepared materials exhibited excellent iodine capture performance at high temperatures, high humidity and irradiation environments. In addition, the iodine-captured Vs-Bi2S3@C could be immobilized into commercial glass compositions. This work demonstrated a viable strategy for constructing adsorbent materials for efficient capture and immobilization of radioiodine through surface defect engineering.