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

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 . 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.