Efficient adsorption of uranium and rhenium using magnetic bentonite: mechanisms and thermodynamics

Abstract The CaFe 2 O 4 –Fe 3 O 4 -bentonite (Bt@CF@F) adsorbent was prepared by sintering and coprecipitation to capture U(VI) and Re(VII) from aqueous environments. A systematic exploration of the influence of operational parameters, including equilibrium time, adsorbent dosage, temperature, pH, and initial concentration, on the removal efficiency of U(VI) and Re(VII) by Bt@CF@F was explored through static adsorption experiments. The results indicate that the adsorption of U(VI) and Re(VII) by the Bt@CF@F conforms to the quasi-second-order model and the Freundlich isotherm model and all reactions were endothermic and can occur spontaneously. The adsorption process is dominated by physical adsorption, accompanied by chemical adsorption. Moreover, Bt@CF@F had a maximum adsorption capacity of 144.33 ± 2.96 mg/g for U(VI) and 233.39 ± 4.70 mg/g for Re(VII). Meanwhile, the SEM, FT-IR, XRD, VSM and XPS analyses revealed that the partial reduction of U (VI) and Re (VII) during adsorption. Consequently, the synthesized Bt@CF@F has the characteristics of large adsorption capacity, environmental friendliness and good stability, making it a powerful choice for cleaning and recovering these elements of U(VI) and Re(VII) from aqueous systems.