A molecular simulation study on the adsorption and separation performance of carbon nanotubes for SO2 in flue gas

To control the emission of SO₂ from flue gas into the atmosphere while considering the capture and collection of greenhouse gas CO₂, the adsorption behavior of a binary mixture of SO₂ and other gases in flue gas (O₂/N₂/H₂O/CO${}_2)$ in (10, 10) carbon nanotube (CNT) was simulated using grand canonical Monte Carlo (GCMC) simulation. The adsorption and separation performance of SO₂ in CNTs with a diameter range of 0.81–1.63 nm for the five-component mixture gas was also analyzed. The findings suggest that the adsorption and separation of SO₂ are primarily influenced by CO₂ (reduction of adsorption capacity by about 50%, separation coefficient of SO₂/CO₂ is lowest) with this effect being more pronounced under high pressure. Meanwhile, it was observed that CNTs with larger pipe diameters exhibit higher SO₂ adsorption capacity, but relatively lower SO₂/CO₂ selectivity and lower stability. On the other hand, CNTs with smaller diameters have relatively lower adsorption capacity for SO₂, but exhibit good selectivity and stability (under different pressure) for SO₂/CO₂. Based on the statistical analysis of SO₂ adsorption capacity and SO₂/CO₂ selectivity, it was determined that (6, 6) CNT with a diameter of 0.81$$nm can exhibit excellent SO₂ adsorption and separation performance at atmospheric pressure, while appropriate large diameter CNTs should be selected for flue gas treatment under high pressure.