Recyclable MFe(2)O(4) (M = Mn, Zn, Cu, Ni, Co) coupled micro–nano bubbles for simultaneous catalytic oxidation to remove NO(x) and SO(2) in flue gas

NO(x) can be efficiently removed by micro–nano bubbles coupling with Fe(3+) and Mn(2+), 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 MFe(2)O(4) to simultaneously remove NO(x) and SO(2) from flue gas, and clarified the effectiveness and reaction mechanism. MFe(2)O(4) (M = Mn, Zn, Cu, Ni and Co) prepared by a hydrothermal method was characterized. The results show that MFe(2)O(4) 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)–SO(2)–MFe(2)O(4)-micro–nano bubble system, while the removal rate of SO(2) can reach 100% at room temperature. The catalytic activities of MFe(2)O(4) showed the following trend: CuFe(2)O(4) > ZnFe(2)O(4) > MnFe(2)O(4) > CoFe(2)O(4) > NiFe(2)O(4). The results provide a new idea for the application of advanced oxidation processes in flue gas treatment.