Nitrogen-doped CNTs enhance heterogeneous Fenton reaction for IOH removal by FeOCl: Role of NCNTs and mechanism

Heterogeneous Fenton has already been used extensively to remove emerging contaminants, however, sluggish Fe(III)/Fe(II) circulation and high mass-transport resistance are its two major limitations. In this study, a novel heterogeneous N-doped carbon nanotubes loaded nano-FeOCl (NCF) catalyst was synthesized by partial thermal decomposition to enhance its catalytic performance. By incorporating NCNTs, the specific surface area of NCF was significantly increased in comparison to FeOCl, which promotes the accumulation of contaminants on the catalyst surface. Similarly, the degradation rate constant (k) of IOH in the NCF/H2O2 system was observed 114 times greater than that of the FeOCl/H2O2 system. Besides not significantly increased k, excessive H2O2 substantially reduced H2O2 utilization. Electron paramagnetic resonance and electrochemical analysis reflected that the NCNTs facilitated the Fe(III)/Fe(II) circulation by improving electron transfer and enhanced •OH, O2•− and 1O2 availability by exerting a confinement effect. The major reactions assumed in IOH degradation include hydrogen atom abstract, amide hydrolysis, deiodination reaction, •OH radical adduct formation, and oxidation of C-OH. This study elucidates the degradation mechanism of IOH in the heterogeneous Fenton system with carbon-based co-catalysts and provides an efficient measure for removing emerging contaminants from the environment.