Accelerating Fe(iii)/Fe(ii) redox cycling by Zn⁰ in micro-nano dendritic Fe-Zn alloy for enhanced Fenton-like degradation of phenol

The sluggish Fe³⁺/Fe²⁺ cycling and nanocatalyst agglomeration are still the great challenges limiting the industrial application of Fenton-like processes. Herein, Fe-Zn alloy catalysts with micro-nano dendritic morphology were prepared by a simple electrodeposition method with FeSO₄·7H₂O and ZnSO₄·7H₂O as metal sources, which were characterized using SEM, EDS, XRD and XPS. The effects of electrolyte composition, current density and electrodeposition time on the performance of the catalysts were investigated. Compared with zero-valent iron (ZVI) or zero-valent zinc (ZVZ), the obtained Fe-20Zn catalysts displayed satisfactory Fenton-like degradation properties, which could almost completely remove phenol within 20 min and be repeatedly used for six times. The removal rate of phenol slowed down with an increase of cycle times. It took 180 min for the sixth cycle to remove 95.14% phenol, due to zinc loss, nanosheet degradation and ZVI species oxidation on the surface. Through free radical scavenging experiment, it was confirmed that hydroxyl radical was the main active species in phenol degradation. The degradation mechanism demonstrated the dominant role of Zn in promoting Fe(iii)/Fe(ii) cycle for improving phenol degradation performance. This study will promote the application of bimetallic Fenton-like catalysts in treatment of wastewater containing organic contaminants.