Simultaneous Deep Dehalogenation and Mineralization of Refractory Halogenated Organics in the ZVI-Water System: A Synergistic Reduction–Oxidation Process via the Reconstruction of the Hydrogen-Bond Network

Abstract

The synergistic redox process has emerged as an innovative strategy for the complete mitigation of refractory halogenated organics. However, constructing an in situ oxidation–reduction coupling in the ZVI-water system remains challenging due to cross-quenching. Herein, a bifunctional ZVI-NFNi catalyst was engineered by incorporating NH4F to reconstruct the hydrogen-bond network of adsorbed water, which created a micropartition to couple atomic hydrogen (H*) reduction with active oxygen (•OOH) oxidation. Experimental and theoretical analyses revealed that NH4F disrupted tetrahedral H-bonding of H2O via strong F/N–H···[OH···OH2]δ+ interactions, thereby accelerating H2O splitting and H* generation, which dramatically enhanced nucleophilic dechlorination of 4-chlorophenol (4-CP) to 93.8%, with a rate constant (0.87 min–1) of 12.2 times higher than that of ZVI-Ni. More significantly, the hydrogen bond electrostatic gradients of NH4F on ZVI-NFNi enhanced *O stabilization at N sites, while H* was trapped at F sites. These micropartitions promoted H*-driven *O reduction to •OOH (H* + O2 → *OOH), thus oxidizing the residual carbon skeleton and significantly raising the mineralization efficiency of 4-CP to 87.6% (vs 29.1% for ZVI-Ni). This study innovatively integrates in situ redox partition in ZVI-H2O systems through the reconstruction of hydrogen-bond networks, offering a synergistic strategy for the complete detoxification of refractory halogenated pollutants.