Title : Development of an iron-catalyzed peroxide oxidation system for efficient atmospheric NOx remediation
Abstract:
Nitrogen oxides (NOx) are significant air pollutants that come from combustion-related activities and vehicle exhaust. NOx are responsible for photochemical smog, acid rain, secondary particulate formation, and adverse human health effects. In this study, a comparative investigation of peroxide-based oxidation systems for NOx remediation was conducted under acidic conditions using homogeneous and heterogeneous iron catalysts. A custom-built sealed reaction chamber was developed to simulate controlled NOx generation and oxidation processes. NO2 generated through the reaction between copper turnings and concentrated nitric acid was exposed to three oxidation systems: (i) H2O2 alone, (ii) homogeneous Fe2+/ H2O2 Fenton oxidation, and (iii) heterogeneous Fe2O3/ H2O2 oxidation. The resulting nitrate (NO??) formation was quantified using UV-Visible spectroscopy and ion chromatography (IC) to evaluate oxidation efficiency. UV-Visible spectroscopic analysis confirmed NO3- ion formation in the peroxide-only system, which achieved a moderate NOx removal efficiency of 24.7%. The addition of Fe2+ significantly enhanced oxidation performance through Fenton-mediated.OH radical generation that yielded a maximum NOx removal efficiency of 85.6% at 5% H2O2 concentration. In contrast, the Fe2O3-assisted heterogeneous system exhibited comparatively lower but stable catalytic activity that achieved 29.2% removal efficiency under identical peroxide concentration. IC analysis consistently identified NO3- as the dominant oxidation product in both catalytic systems which confirmed effective oxidative conversion of gaseous NO2 into stable aqueous NO3- species. The results demonstrate that catalyst-assisted peroxide activation substantially improves NOx oxidation efficiency. Homogeneous Fenton chemistry provided superior performance due to rapid bulk-phase hydroxyl radical production. Although the heterogeneous hematite system displayed lower activity, its operational stability and potential catalyst recoverability demonstrate its suitability for sustainable NOx treatment processes. This study establishes an effective laboratory-scale framework for peroxide-assisted NOx remediation and provides important mechanistic insight into iron-mediated oxidation pathways for the development of low-cost and environmentally sustainable atmospheric NOx control technologies.
Keywords: NOx, hydrogen peroxide, Fenton reagent, air pollution, ion chromatography
