Low-Temperature Conversion of NO in Flue Gas by Vaporized H2O2 and Nanoscale Zerovalent Iron

To remove NO from coal-fired flue gas at a low temperature and avoid secondary pollutions of the current selective catalytic reduction (SCR) system, a high-reactive catalyst, nanoscale zerovalent iron (nZVI), was prepared and used to activate vaporized H2O2 for NO conversion. Effects of various factors on NO conversion were investigated, i.e., the H2O2 concentration and pH, gas flow velocity, reaction temperature, and coexisting gases, and the optimal NO conversion efficiency of 80.4% was obtained at 120 °C with a gas hourly space velocity of 198 726 h–1. The physicochemical properties of the fresh and spent nZVI were characterized through X-ray diffraction (XRD), Fourier transformation infrared spectrometry (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), from which the formation of iron oxide and the aggregation of catalyst after reaction were confirmed, resulting from the electron transfer between nZVI and H2O2 and the continuous release of Fe2+/Fe3+. Meanwhile, the methylene blue experiments were accomplished to indirectly prove the production of HO•, and the continuity tests were performed to assess the stability of the catalyst. The conversion mechanism was speculated on the basis of the characterizations of nZVI, analyses of conversion products, and literature references.