Insight into the Enhanced Removal of U(VI) with Fe–Ni Bimetallic Particles Loaded on Biochar

This work develops Fe–Ni particles loaded on biochar (Fe–Ni/BC) to remove U(VI) efficiently. Fe–Ni bimetallic particles loaded on biochar (BC) can improve stability and reactivity, and the mesoporous structure of BC can effectively reduce Fe⁰ aggregation. The removal ability of Fe–Ni/BC is higher than that of Fe–Ni, BC, and Fe/BC. With the aid of kinetics and isotherms, the removal data were fitted by the pseudo-second-order kinetic model (R² ≥ 0.999) and Langmuir model (R² ≥ 0.94). Meanwhile, Fe–Ni/BC exhibited the largest removal capacity of 250.78 mg/g for U(VI) at pH 5.0 and a temperature of 303 K. Removing uranium using Fe–Ni/BC was carried out in the following steps: First, U(VI) in the solution was sorbed onto the Fe–Ni/BC surface through chemical bonds. Second, Fe(II) and Fe⁰ contributed to the U(VI) reduction process. At the same time, Fe–Ni formed a primary cell and underwent electron transfer. Moreover, Ni⁰ adsorbed H₂ generated by Fe⁰ corrosion, forming Ni–H to prevent agglomeration and reduce U(VI). The results indicate that Fe–Ni bimetallic particles loaded on biochar enhance the removal of U(VI) by sorption-reduction synergistic effect. This work offers valuable insights into the design of bimetallic nanomaterials for environmental remediation of U(VI) contamination.