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.