Screening of New bio-based materials for radioactive iodide adsorption from water environment

Several bio-based adsorbents containing cations were screened for radioactive iodide removal from a water environment. The efficiency of the selected adsorbents was assessed in different pH, temperature as well as competitive ions. Based on the adsorption capacity, iron-alginate (Fe-Alg), hazelnut shells, and sacha inchi shells were selected as potential adsorbents. They possessed 139, 18.9, and 45.1 mg/g iodide (I−) adsorption capacities, respectively. The adsorption equilibrium time for Fe-Alg was 30 min, while hazelnut shells and sash inchi shells took 120 min to stabilize. The adsorption results fit the Langmuir isotherm model with predicted adsorption capacities similar to those of the experimental data. The fitting of pseudo-first-order reaction and the negative values of the Arrhenius activation energy inferred that the adsorption had a physical nature. The iodine X-ray absorption edges of 4552.83–4553.40 eV from the near-edge structure analysis confirmed the physisorption, as the I− in bio-based adsorbents did not go through any chemical transformation. Fe3+ was used to synthesize Fe-Alg. With an energy dispersive X-ray analysis, magnesium, potassium, and calcium were detected in the hazelnut shells and sacha inchi shells. Consequently, the binding of I− to the surface of the adsorbents was mainly through electrostatic forces, with the cationic species on the surface of the adsorbents. The selected bio-based adsorbents could be used for industrial effluents in natural water environments as they exhibited I− adsorption at various pH levels, temperatures, and in the presence of competitive anions.