Simultaneous removal of NO and SO 2 from flue gas using vaporized H 2 O 2 catalyzed by nanoscale zero-valent iron

Abstract

To remove NO and SO₂ from flue gas simultaneously, a heterogeneous catalytic oxidation system was developed with the nanoscale zero-valent iron (nZVI), vaporized H₂O₂, and sodium humate (HA-Na) acting as the catalyst, oxidant, and absorbent, respectively. The experimental results indicated that the desulfurization was mainly influenced by the absorption, and the denitrification was significantly affected by the catalytic oxidation parameters. Under the optimal conditions, the simultaneous removal efficiencies of SO₂ and NO were 100 and 88.4%, respectively. The presence of ^·OH during the removal process was proved by the scavenger tests, and the production of ^·OH with and without nZVI was indirectly evaluated by the electron paramagnetic resonance (EPR) and methylene blue experiments. Moreover, the fresh and aged nZVI were characterized by a series of techniques and the results suggested that the redox pair Fe²⁺/Fe³⁺ released by nZVI could react with H₂O₂ to provide the sustainable ^·OH, which was important for the oxidation from NO and SO₂ to NO₃⁻ and SO₄²⁻. The removal mechanism was proposed preliminarily based on the correlative experiments, characterizations, and references.