Oxidative Degradation of Aniline by Ferrate-Hydrogen Peroxide System: Unveiling pH-Dependent Mechanisms and Pathways

This study systematically investigated the efficacy and underlying mechanisms of aniline degradation in a Ferrate (Fe(VI))-hydrogen peroxide (H₂O₂) system.The effects of key operational parameters, including H₂O₂ dosage, initial pH (3-11), and reaction temperature (10-60ºC), were evaluated.Under optimal conditions (10 mM Fe(VI), 176 mM H₂O₂, 30ºC, 30 min), high aniline removal efficiencies of 91±0.3% and 88±0.2% were achieved at pH 3.0 and 7.0, respectively.Radical quenching experiments with tert-butanol, coupled with kinetic modeling, revealed a critical pH-dependent mechanistic shift.Under acidic conditions (pH 3.0), the degradation followed pseudo-second-order kinetics (kₐₚₚ = 0.03425 mM⁻¹•min⁻¹), with hydroxyl radicals (•OH) identified as a primary oxidizing species.In contrast, under alkaline conditions, the process was dominated by high-valent iron species (Fe(IV)/Fe(V)) and direct electron transfer by Fe(VI), adhering to pseudo-first-order kinetics (maximum kₐₚₚ = 0.07319 min⁻¹).Fourteen intermediate products were identified via liquid chromatography-mass spectrometry (LC-MS), leading to the proposal of four potential degradation pathways.This work provides fundamental insights into the pH-dependent mechanisms of the Fe(VI)/H₂O₂ system and proposes a promising, sustainable strategy for the treatment of aniline-containing industrial wastewater.