New Insights into the Role of Crystalline Fe3P in Phosphatized Zerovalent Iron for Enhancing Advanced Oxidation Processes and Storage Stability

Zerovalent iron (ZVI) is a widely utilized remediation agent for contaminated soil and groundwater; however, it has consistently faced the challenge of balancing catalytic activity with storage stability. Herein, submicron ZVI particles were phosphatized to produce phosphatized ZVI (P-ZVI), which was employed to activate peroxydisulfate (PDS) for phenol degradation. As anticipated, phosphatization significantly enhanced both the storage stability (>10 months vs 1 d) and catalytic activity (4.37 vs 0.12 L m–2 h–1) of ZVI compared to unphosphatized counterparts attributed to the formation of a crystalline Fe3P shell on P-ZVI. This Fe3P shell selectively interacts with H2O/O2/PDS, maintaining the stability of P-ZVI under high humidity and oxygen conditions while creating mass transfer channels that enhance reactivity in the presence of PDS. Characterization results from the reaction process demonstrated that the Fe3P shell activated PDS through both direct (via Fe cations) and indirect pathways (through a phosphorus anion-mediated Fe3+/Fe2+ cycle), generating reactive species and facilitating mass transfer between core Fe0 and external PDS for efficient PDS activation and phenol degradation. This study elucidates how constructing an Fe3P shell can realize selective activation of PDS while simultaneously enhancing both the storage and catalytic stabilities of ZVI, thereby boosting the practical application of PDS-based advanced oxidation processes in various environmental remediation.