Adsorption Behavior of Co2+, Ni2+, Sr2+, Cs+, and I- by Corrosion Products α-FeOOH from Typical Metal Tanks

Throughout the nuclear power production process, the disposal of radioactive waste has consistently raised concerns about environmental safety. When the metal tanks used for waste disposal are corroded, radionuclides seep into the groundwater environment and eventually into the biosphere, causing significant damage to the environment. Hence, investigating the adsorption behavior of radionuclides on the corrosion products of metal tanks used for waste disposal is an essential component of safety and evaluation protocols at disposal sites. In order to understand the adsorption behavior of important radionuclides 60Co, 59Ni, 90Sr, 135Cs and 129I on α-FeOOH, the influences of different pH values, contact time, temperature and ion concentration on the adsorption rate were studied. The adsorption mechanism was also discussed. It was revealed that the adsorption of key nuclides onto α-FeOOH is significantly influenced by both pH and temperature. This change in surface charge corresponds to alterations in the morphology of nuclide ions within the system, subsequently impacting the adsorption efficiency. Sodium ions (Na+) and chlorate ions (ClO3-) compete for coordination with nuclide ions, thereby exerting an additional influence on the adsorption process. The XPS analysis results demonstrate the formation of an internal coordination bond (Ni-O bond) between Ni2+ and iron oxide, which is adsorbed onto α-FeOOH.

Efficient and selective adsorption of U(VI) by succinic acid modified iron oxide adsorbent

The iron oxide surface was modified with succinic acid moiety and the adsorbent obtained, Fe-SUC, was evaluated for the adsorption of U(VI) (Uranium (VI)) from aqueous solution. The Fe-SUC was characterized by FT-IR (Fourier Transform Infrared Spectroscopy), Raman spectroscopy, thermogravimetry, X-ray diffraction, SEM-EDX (Scanning Electron Microscope - Energy-dispersive X-ray Spectroscopy), and particle size analysis. The adsorption behavior of U(VI) on Fe-SUC was studied as a function of pH, contact time, and concentration of U(VI) in the aqueous phase. The adsorption of U(VI) increased with increase in the pH of aqueous phase, and the adsorption saturation occurred at pH = 6. The kinetic data obtained for the adsorption of U(VI) on Fe-SUC were modeled with the pseudo-first-order and pseudo-second-order rate models. Similarly, the U(VI) adsorption isotherm was fitted with Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich adsorption isotherm models. The Langmuir adsorption capacity of U(VI) on Fe-SUC was about ∼176 mg g−1. The selectivity of the adsorbent toward U(VI) was evaluated in the presence of several possible interfering ions. The adsorbed U(VI) was recovered by 0.5 M sodium carbonate solution and the spent adsorbent was tested for its reusability.