Simultaneous removal of SO2 and NO by FeII(EDTA) solution: promotion of Mn powder and mechanism of reduction

The effect of Mn powder addition on the simultaneous removal of SO 2 and NO coupled with Fe II (EDTA) absorption was investigated in this work. In the NO absorption system with Fe II (EDTA), SO 2 reduced Fe II (EDTA)-NO to Fe II (EDTA) with a reduction efficiency reaching 88.5% under the conditions of 4000 mg/m 3 SO 2 , pH 8.0, 44 °C, and the flow rate of 1.2 L/min within 60 min. Introducing 0.1 M Mn powder with SO 2 increased the Fe II (EDTA)-NO reduction efficiency to 96.8% within 5 min. SO 2 was also removed by reducing Fe II (EDTA)-NO and converted into SO 4 2- at a removal efficiency of 100%. After adding Mn powder, NO was removed through the following reaction: \( 5\mathrm{Mn}+2{\mathrm{Fe}}^{\mathrm{II}}\left(\mathrm{EDTA}\right)-\mathrm{NO}+12{\mathrm{H}}^{+}\longrightarrow 2{\mathrm{Fe}}^{\mathrm{II}}\left(\mathrm{EDTA}\right)+5{\mathrm{Mn}}^{2+}+2{\mathrm{NH}}_4^{+}+2{\mathrm{H}}_2\mathrm{O} \) . Mn powder functioned as a reductant to regenerate the absorption of solution, and the coordinated NO in Fe II (EDTA)-NO was reduced to NH 4 + . The resource utilization rate of N reached approximately 77.2%. The integrated technology is a potential solution for flue gas treatment in industrial sectors with coal-fired power plants and industrial boiler. Graphical abstract