Sorption of Uranium and Plutonium Species over Mn-Doped Fe₃O₄ Nanoparticles Dispersed in KIT-6: A Thermodynamically...

The sorption of UO₂²⁺ and PuO₂²⁺ ions over mesoporous magnetic nanoparticles (MNPs) has garnered quite a bit of importance lately. Apart from different sorption studies with higher concentrations of UO₂²⁺ and PuO₂²⁺ ions, limited studies are available for the sorption of both UO₂²⁺ and PuO₂²⁺ ions together at the ultratrace level. The effect of different thermodynamic and kinetic parameters owing to different structural attributions affecting sorption efficiency has always been the gray area. This present manuscript deals with the sorption of both UO₂²⁺ and PuO₂²⁺ ions over the MNPs, which were dispersed in a silica-based mesoporous material called KIT-6 (Korea Advanced Institute of Science and Technology). The sorption behavior in these materials was investigated in terms of different structural parameters using several characterization techniques like X-ray Photoelectron Spectroscopy (XPS), zeta potential, Mössbauer spectroscopy, Brunauer-Emmett-Teller (BET) surface area analysis, Fourier Transform Infrared (FTIR) Spectroscopy, and High-Resolution Transmission Electron Microscopy (HRTEM). These provide deep insights for the different structural factors such as surface charge, surface hydroxyl groups, particle size, and magnetic properties governing their sorption mechanism and capabilities. These materials uniquely show very high K_d values for sorption of both UO₂²⁺ (8.34 × 10³ mL/g) as well as PuO₂²⁺ ions (4.75 × 10⁴ mL/g) under optimized conditions like pH, temperature, and analyte concentration. Isotherm modeling studies show highly comparable sorption capacity for UO₂²⁺ ions (66.31 mg/g) following Langmuir adsorption behavior. It was established that mainly the thermodynamic parameters govern the sorption efficacy and not the kinetic parameters. Selectivity for the materials toward UO₂²⁺ and PuO₂²⁺ ions individually was tested in the presence of different interfering ions.