Engineering built-in electric fields via tuning electronic structure in activated carbon supported sulfidized nanoscale zero-valent iron for highly efficient removal of florfenicol under ambient conditions

The urgent need for sustainable water purification technologies to remove halogenated pollutants, particularly antibiotics, continues to drive innovation in environmental remediation. In this study, we propose a simple and scalable strategy to develop an activated carbon supported sulfidized nanoscale zero-valent iron (S-nZVI-AC) for efficient florfenicol (FF) removal under ambient conditions. Leveraging the synergistic interplay of sulfidation and carbon support, S-nZVI-AC outperformed conventional nZVI systems, delivering a high-rate constant (k₁ = 0.39 min^-1) and surface-area-normalized activity (k_SA = 9.94 mL m^-2 min^-1). Experimental results and DFT calculations demonstrated that the rectifying contacts between S-nZVI and AC generated built-in electric fields, reprogramming the interfacial electronic structure and accelerating electron transfer. This facilitated halogen bond cleavage and reactive site exposure, effectively overcoming the kinetic bottleneck in FF degradation. S-nZVI-AC exhibited strong environmental compatibility, achieving >90 % FF removal in natural waters and 70 % in pharmaceutical wastewater, while substantially reducing post-reaction toxicity and posing negligible material-associated hazards. This work offers a viable route to tailor interfacial electronic structures via synergistic sulfidation-carbon coupling and offers new insights into the rational design of high-efficiency, low-consumption remediation materials for sustainable water purification.