Defect engineering of zero-valent iron promotes interfacial electron transfer for efficient Fenton-like activation at low catalyst dosage

Zero-valent iron (ZVI)-activated persulfate systems are limited by sluggish Fe cycling and rapid surface passivation, resulting in inefficient electron utilization and excessive reagent consumption. Here, we develop a NaCl-assisted ball milling strategy to construct a defect-rich ZVI interface (Cl-D-ZVI) with enhanced electron transfer capability. NaCl-assisted ball milling induces local structural disorder and coordination reconstruction at the ZVI interface, facilitating interfacial electron transfer and Fe redox transformation. Cl-D-ZVI enables efficient persulfate activation at a low catalyst dosage (20 mg·L^-1), exhibiting consistently higher degradation activity than conventionally ball-milled ZVI. Mechanistic investigations reveal that the defective interface reduces the solid-liquid electron transfer barrier and facilitates Fe redox transformation, thereby promoting the concurrent formation of ·OH and Fe(Ⅳ)=O species. Continuous-flow filtration demonstrates sustained reactivity under different water matrices, while life-cycle assessment indicates reduced environmental impacts of the developed system. This study provides a scalable defect-engineering strategy for improving electron utilization and advancing sustainable iron-based advanced oxidation processes.