Synergistic adsorptive reduction for enhanced U(VI) recovery from seawater via Fe3S4-decorated biochar nanosphere hybrids

Abstract Herein, the in situ growth strategy successfully facilitated the synthesis of a novel BN-PDA@Fe 3 S 4 composite through the integration of polydopamine-functionalized biochar nanospheres (BN-PDA) with Fe 3 S 4 . A suite of characterization techniques was employed to elucidate the microscopic morphology and crystallographic structure of the as-prepared adsorbent. Experimental results indicated that at 298 K and pH 5, the maximum U(VI) adsorption capacity of BN-PDA@Fe 3 S 4 reached 203.4 mg g −1 , along with a remarkable improvement in the removal efficiency. The adsorption behavior of BN-PDA@Fe 3 S 4 toward U(VI) was well described by the Langmuir isotherm model and Pseudo-second-order kinetic model, which confirmed the monolayer chemical adsorption nature of the process. Thermodynamic analyses further demonstrated that the U(VI) adsorption process was spontaneous and endothermic. Mechanistic investigations revealed that U(VI) ions could be reduced to less toxic U(IV) species, with this reduction process promoted by the reductive Fe(II) and S(-II) moieties in the Fe 3 S 4 component. Collectively, this study provides a promising research avenue for the extraction of uranium from seawater. Graphic Abstract