One-Step Synthesis of Silver-Decorated Reduced Graphene Oxide Nanocomposites for Effective Elimination of Iodide Anions from Water

Water contamination by radioactive iodide raises public concerns due to potential threats to human health and ecosystems. In this study, we synthesized Ag/RGO-4, anchoring nanosilver (Ag) onto reduced graphene oxide (RGO), and verified its efficacy for selective iodide removal. The structure, surface morphology, and functional group composition of the composite material were thoroughly characterized. Iodide adsorption properties, encompassing pH effect, kinetics, equilibrium isotherm, anions' influence, and column test, were systematically evaluated. Batch tests revealed that RGO addition increased silver's iodide adsorption capacity from 0.87 to 2.06 mmol g(-1) at neutral pH. pH variations had minimal impact, as Ag/RGO-4 relied on AgI precipitate formation. The maximum adsorption capacity was 2.9 mmol g(-1). Ag/RGO-4 selectively removed iodide in the presence of interfering anions (CO32-, SO42-, NO3-, Cl-) at 266 mmol L-1, with minimal iodide removal enhancement. After batch test analysis and using comprehensive analytical techniques (XRD, SEM, TEM, FTIR, and XPS), a plausible adsorption mechanism emerged. Hypothesized is the initial oxidation of Ag by C=O groups on RGO in Ag/RGO-4, producing Ag+, leading to iodide sequestration as AgI. The material holds promise for treating iodide-contaminated water from nuclear incidents and nuclear medicine.