Sulfur dioxide absorption by novel green solvents of deep eutectic solvents: Modeling screening

Sulfur dioxide (SO₂), produced mainly from the combustion of coal, is the most important cause of acidic rain, skin diseases, and environmental issues. To overcome the environmental problems, SO₂ must be captured on an industrial scale before it is released into the air. In chemical industries, organic solvents are used for partial absorption of SO₂. However, those organic solvents have negative environmental effects. Thus, proposing environmentally friendly and green solvents for SO₂ absorption is vital for industries. Recently, increased attention has been paid to capturing SO₂ using Deep Eutectic Solvents (DESs) as the most recently introduced category of green solvents. This study performed a comprehensive screening study on the investigation of the performance of various simple and complicated models for SO₂ solubilities in a wide range of different nature DESs. For this purpose, the most updated and largest SO₂ solubility data bank in DESs involving 976 data points for 63 different nature DESs over wide temperature and pressure ranges has been gathered from open literature. For model screening, for the physical absorption models, the performances of SRK and CPA as the simple cubic and complicated sophisticated equations of state, NRTL and UNIQUAC as the well-known activity coefficient models, and for the chemical absorption models, RETM were investigated and compared. For physical absorption models, coupling an equation of state with the UNIQUAC activity coefficient model i.e. CPA-UNIQUAC, SRK-UNIQUAC, and also using simple SRK-SRK models led to the best performances. Compared to all investigated models, RETM as the chemical absorption model showed the best performance with the AARD% value of 12.95. This shows the importance of considering the chemical absorption mechanism for SO₂ absorption by DESs. Finally, general guidelines for using different modeling approaches were proposed to be considered by the researchers.