Scalable synthesis of nanoscale sulfurized zero-valent iron via wet mechanochemical milling for efficient catalytic degradation of phenol in water treatment.

The scalable and cost-effective synthesis of high-performance nanoscale zero-valent iron (nZVI) catalysts remains a critical bottleneck for the practical implementation of advanced oxidation processes (AOPs) in water treatment. Herein, we report a facile and scalable wet mechanochemical strategy for synthesizing sulfurized nZVI (S-nZVI) via alkaline sulfidation-assisted sand milling using sodium sulfide and ammonium hydroxide. This strategy enables the uniform production of S-nZVI particles with sizes of 56.3-174.1 nm, achieving 4.5- and 2.2-fold increases in Fe0 electron utilization efficiency and 179- and 657-fold enhancements in the phenol degradation rate constant compared with pristine commercial ZVI and sand-milled nZVI, respectively. The conductive FeSx shell facilitates rapid electron transfer from the Fe0 core for peroxydisulfate (PS) activation, while surface-unsaturated sulfur species (e.g., S2-, S22-, Sn2-) promote proton capture and accelerate the rate-limiting Fe(III)/Fe(II) cycling, thereby enhancing PS activation and reactive species generation. Furthermore, the synthesis strategy was successfully scaled to the tens-of-kilograms level, yielding S-nZVI with high Fe0 content and exceptional pH adaptability (90.599.6% degradation efficiency of phenol over pH 3-11). This work provides mechanistic insights into the structure-activity relationship of sulfurized ZVI and establishes wet mechanochemical synthesis as a scalable platform for the rational design and preparation of high-performance iron-based catalysts for environmental remediation.