Three-dimensional printed zerovalent iron enables selective and sustained reductive dehalogenation of florfenicol via structure-induced corrosion resistance and electron transfer regulation.

Zero-valent iron (Fe0) is widely applied for reductive dehalogenation but is limited by inefficient electron utilization and rapid corrosion in aqueous environments. Herein, 3D printing was employed to engineer the structural and interfacial properties of Fe0 for enhanced reductive transformation of florfenicol (FLO) under anoxic conditions. Compared with pristine Fe0 powders, the 3D-printed Fe0 (3DP-Fe0) exhibited a hierarchical porous architecture, lattice expansion, and enhanced hydrophobicity, which collectively regulated Fe0 corrosion behavior and interfacial electron transfer. These structural and interfacial modifications improved electron utilization efficiency toward FLO dehalogenation while suppressing non-productive hydrogen evolution. Mechanistic investigations revealed that atomic hydrogen was the dominant reactive species responsible for sequential FLO dechlorination. Benefiting from regulated corrosion and preserved Fe0 reactivity, 3DP-Fe0 maintained high FLO removal efficiency during repeated cycles and prolonged anoxic aging, accompanied by substantially reduced Fe0 consumption and Fe leaching. Transformation products generated through sequential dechlorination exhibited markedly decreased antibacterial activity, indicating effective toxicity reduction during FLO degradation. Furthermore, 3DP-Fe0 retained robust performance in complex water matrices and enabled efficient removal of other recalcitrant pharmaceuticals, demonstrating its broad applicability. Overall, this study highlights 3D printing as an effective strategy to enhance Fe0 reactivity and stability for the efficient reductive treatment of emerging contaminants.