Simultaneous oxidation removal of NO and SO2 in simulated flue gas stream via a UV-light/composite oxidant system

In this work, an ultraviolet light (UV-light)/composite oxidant oxidation system based on an impinging stream absorber has been constructed, and then used for synchronously removing NO and SO₂ in simulated flue gas. The influences of process variables on NO/SO₂ oxidation processes, removal mechanisms, enhancement mechanisms, and macro-kinetics were studied. This system constructed can realize superior simultaneous desulfurization and denitrification efficiency owing to the synergistic effects of composite oxidant under far lower reagent and smaller energy consumption. The simultaneous removal efficiency of 98.9 % for NO and 100 % for SO₂ was achieved in the UV-light/composite oxidant oxidation system, far exceeding the systems induced via a single oxidant. The concentrations of H₂O₂ and S₂O₈^2-, operation temperature, and solution pH value have a dual influence on the NO removal efficiency, and the optimized values are 0.1 mol/L, 0.1 mol/L, 60℃ and 2.48, respectively. The utilization rate of free radicals in liquid phase is greatly improved owing to the interaction between the two oxidants, which is attributed to the crucial role of H₂O₂ as a free radical capture intermediate in this system. For the NO removal, oxidation via hydroxyl radical played the most key role and oxidation via sulfate free radical played a second key role. Oxidation by peroxides played a significant role in SO₂ removal. The NO absorption process in the UV-light/composite oxidant oxidation system was determined to be a pseudo-first-order rapid reaction kinetic characteristic.