Synthesis and characterization of Cu-Cu2O/reduced graphene oxide for enhanced iodide adsorption through multiple pathways

Fabricating efficient copper-based adsorbents for radioactive iodine removal is crucial for environmental protection and waste volume reduction, particularly in the treatment of radioactive waste from hospitals. In this study, a composite of reduced graphene oxide (RGO) supported by Cu-Cu 2 O nanocrystals (Cu-Cu 2 O/RGO-3) was synthesized via a one-step method and evaluated for its effectiveness in iodide removal from water. The composite was comprehensively characterized using XRD, SEM, FT-IR, and XPS analyses. The effects of copper content, pH, contact time, iodide concentration, temperature, and coexisting anions on iodide uptake were systematically investigated. In the Cu-Cu 2 O/RGO-3 composite, copper primarily existed as metallic Cu, along with a small amount of Cu 2 O. Cu-Cu 2 O/RGO-3 exhibited a significantly higher I - adsorption capacity compared to Cu powder, effectively reducing I - concentrations from 8.6 to 0.029 mg/L within just 3 min, demonstrating a rapid uptake rate for trace I - . Furthermore, the maximum adsorption capacity reached 152.1 mg/g at pH 7.0, surpassing that of many reported copper-based adsorbents. The composite showed selectivity in the presence of competing ions like Cl - , NO 3 - , and SO 4 2- , but HCO 3 - at higher concentrations inhibited I - adsorption. Post-adsorption analysis revealed that iodine was present solely as CuI. XPS analysis indicated that residual carboxyl groups in RGO facilitated the oxidation of Cu and promoted redox reactions between Cu(OH) 2 and Cu, providing multiple pathways for generating additional Cu + ions, thereby enhancing I - adsorption. This study offers a practical approach for modifying carbon-based materials with copper compounds, emphasizing the potential of copper-based materials for effective iodide purification in wastewater treatment.