Highly efficient activation of peroxides by Fe-BDC-NH2 encapsulated nano zero-valent iron composite catalyst for the degradation of chlorophenols

Abstract

Chlorinated pollutants, particularly chlorophenols, present a significant concern to ecosystems due to their persistence and toxicity, necessitating the development of effective methods for their elimination from water bodies. In this study, we synthesized a novel nZVI@Fe-MIL-101 catalyst through the reduction of nZVI by NaBH₄ and its subsequent encapsulation within Fe-MIL-101, creating a unique core–shell structure. The synthesized nZVI@Fe-MIL-101 catalyst could be effectively utilized for the removal of 2,4-dichlorophenol via an activated hydrogen peroxide-mediated Fenton reaction. The synthesized nZVI@Fe-MIL-101 demonstrated a remarkable enhancement in catalytic performance, with an 11.6-fold increase in the chlorophenol removal rate compared to the unmodified MIL-101(Fe) catalyst. Comprehensive mechanistic investigations using XPS and EPR revealed that nZVI served as the main active substance, with the Fe(II)/Fe(III) cycle providing the primary driving force for H₂O₂ activation. The π-π interactions between the catalyst and 2,4-dichlorophenol molecules facilitated effective adsorption of 2,4-dichlorophenol onto the catalyst surface. Moreover, the Fe-BDC-NH₂ skeleton not only serves a protective function but also, through the incorporation of nitrogen via the amino group, offered a reactive site for the generation of ¹O₂ and facilitated electron transfer, further activating O₂ to produce ¹O₂. the 2,4-dichlorophenol molecule was ultimately degraded by the combined action of ⋅OH radicals and ¹O₂ non-radicals. This study demonstrates that nZVI@Fe-MIL-101 exhibits excellent stability and recyclability, making it a promising multiphase catalyst for the treating of chlorophenolic compounds.