Highly efficient removal of radioactive iodine from solution using in situ prepared Cu⁰@ACF adsorbent

Rapid and efficient removal of radioactive iodine from nuclear accidents and effluent waste was significantly essential to protect the living environment and maintain human health. The nano-zero-valent copper modified activated carbon fiber (Cu⁰@ACF) composite was successfully synthesized via an in situ self-reduction method. The structural and chemical compositions of both pristine and iodine-adsorbed samples (ACF and Cu⁰@ACF) were systematically analyzed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The coexistence of carbon and copper was verified using energy dispersive spectroscopy (EDS). The effects of modifier concentration, contact time, pH value and interfering ions on the removal of I₂ and I^- were comprehensively investigated through batch experiments. The adsorption capacity of 4 wt% Cu⁰@ACF for I₂ reached 980 mg/g (C₀ = 1000 mg/L, pH = 2), and for I^- was 358 mg/g (C₀ = 400 mg/L, pH = 2), significantly outperforming other reported iodine adsorbents. The kinetic studies revealed that the adsorption processes followed pseudo-second-order kinetics, while isotherm data were best described by the Langmuir model (R² > 0.99), indicating monolayer chemisorption. The adsorption mechanism was dominated by chemical reactions where in iodide ions (I^-) interact with the metallic nano‑copper (Cu⁰) anchored on the ACF surface, resulting in the formation of CuI characterized by polar covalent bonding. In a word, Cu⁰@ACF showed an outstanding potential for radioactive wastewater treatment applications and this work presents a facile strategy for developing high-performance ACF-based adsorbents.