Recyclable MFe2O4 (M = Mn, Zn, Cu, Ni, Co) coupled micro–nano bubbles for simultaneous catalytic oxidation to remove NOx and SO2 in flue gas

Abstract

NO_x can be efficiently removed by micro–nano bubbles coupling with Fe³⁺ and Mn²⁺, but the catalyst cannot be reused and the adsorption wastewater should be treated. This work developed a new technology that uses micro–nano bubbles and recyclable MFe₂O₄ to simultaneously remove NO_x and SO₂ from flue gas, and clarified the effectiveness and reaction mechanism. MFe₂O₄ (M = Mn, Zn, Cu, Ni and Co) prepared by a hydrothermal method was characterized. The results show that MFe₂O₄ can be activated to produce ˙OH which can accelerate the oxidation absorption of NO_x. Compared with no catalyst, the NO_x conversion rate increased from 32.85% to 83.88% in the NO_x–SO₂–MFe₂O₄-micro–nano bubble system, while the removal rate of SO₂ can reach 100% at room temperature. The catalytic activities of MFe₂O₄ showed the following trend: CuFe₂O₄ > ZnFe₂O₄ > MnFe₂O₄ > CoFe₂O₄ > NiFe₂O₄. The results provide a new idea for the application of advanced oxidation processes in flue gas treatment.