Adsorption Behavior of U(VI) and Re(VII) on Iron Sulfide Nanoparticles Modified with Titanate Nanotubes: Mechanism and Performance Insights

Graphical A novel nanocomposite (TNTs-FeS) was developed for removal of U(VI) and Re(VII) from aqueous solutions. Experiment results revealed that TNTs as a stabilizer for FeS had good stability and prevention FeS agglomeration. The pseudo-second-order kinetic model was both able to adequately interpret the experimental rate data of U(VI) and Re(VII) removal. The U(VI) adsorption affected by the coexisting ions (Cd 2+ and Cu 2+ ) significantly due to competitive adsorption. A novel nanocomposite (TNTs-FeS) was developed by anchoring ferrous sulfide (FeS) nanoparticles immobilized on titanate nanotubes (TNTs) by hydrothermal method to remove U(VI) and Re(VII) from aqueous solution, and the removal mechanism and efficiency were examined. The experimental results showed that the TNTs can effectively improve the dispersibility and stability of FeS. The environmental conditions, including initial solution pH, initial concentration, equilibrium time, and dosage, played an important role in the remediation process, which can affect the immobilization efficiency significantly. The maximum quantity removal of U(VI) and Re(VII) was 291.67 and 226.23 mg/g at pH of 6.0 and 12.0. The adsorption kinetics and the equilibrium isotherms of U(VI) and Re(VII) all fitted well with the pseudo-second-order model ( R 2 >0.99) and the Freundlich model ( R 2 >0.99). The main mechanism of removal by TNTs-FeS was electrostatic attraction, chemical reduction, and surface complexation. Thus, TNTs-FeS composites exhibited a high potential to remove U(VI) and Re(VII) heavy metal ions from the surface and groundwater.