Mechanistic Study of Selective Absorption of NO in Flue Gas Using EG-TBAB Deep Eutectic Solvents

The selective absorption of NO in flue gas has been investigated using a series of deep eutectic solvents (DESs) as novel denitrifying agents. The EG-TBAB DESs used in this work are composed of a hydrogen donor ethylene glycol (EG) and a parent salt tetrabutylammonium bromide (TBAB). Effects of DES composition (EG:TBAB molar ratio), operation temperature, residence time, and O2 concentration in the flue gas on denitrification performances of EG-TBAB DESs have been investigated. The highest denitrification efficiency and capacity were achieved using EG to TBAB molar ratio of 50:1 at an operation temperature of 50 °C. The O2 partial pressure in the flue gas showed no noticeable effects on NO absorption in EG-TBAB DESs. EG-TBAB DESs maintain high denitrification stability after five absorption–desorption cycles. The calculated absorption equilibrium constant (K0) and Henry's law constant (H) showed that EG-TBAB DESs exhibited high absorption capacity for NO molecules, indicating that they are applicable in industrial denitrification processes. The kinetics analysis of NO absorption in EG-TBAB DESs indicated that EG-TBAB DESs could effectively absorb NO and the absorption of NO was strongly influenced by mass transfer.