Simultaneous Removal of NO and SO₂ from Flue Gas Using [Bmim]₂FeCl₄/Sulfolane Binary Mixtures

Abstract

NO and SO2 are the major pollutants of coal combustion. As superior absorbents, ionic liquids are environmentally friendly, are reusable, and can clean flue gases, such as CO2, SO2, and NO x . However, NO and SO2 absorption with low concentration in flue gases under normal conditions is rarely studied. In this work, [Bmim]2FeCl4 was synthesized and mixed with sulfolane for NO and SO2 removal from flue gas. The investigated concentrations of NO and SO2 were 1100 and 2500 ppm, respectively, which are close to real fuel gas conditions. Results showed that 30 wt % [Bmim]2FeCl4/sulfolane mixture performed the best absorption behavior. The presence of SO2 could promote NO absorption by [Bmim]2FeCl4/sulfolane mixture. The 30 wt % [Bmim]2FeCl4/sulfolane mixture had removal efficiencies of 93.6 and 76.2% for NO and SO2, respectively. This mixture also showed great reusability for NO and SO2 after six cycles of absorption. Fourier transform infrared (FTIR) spectrum indicated that SO2 and NO removal by [Bmim]2FeCl4/sulfolane binary mixture was due to the chemical reaction between NO and [Bmim]2FeCl4 and the physical absorption between SO2 and sulfolane.