Effective Absorption Mechanism of SO(2) and NO(2) in the Flue Gas by Ammonium-Bromide-Based Deep Eutectic Solvents

[Image: see text] Simultaneous capture of SO(2) and NO(x) from flue gas is critical for coal-fired power generation. In this study, environmentally friendly and high-performance deep eutectic solvents based on ethylene glycol and ammonium bromide were designed to capture SO(2) and NO(2) simultaneously. The SO(2) and NO(2) absorption performances and absorption mechanisms were systematically investigated by (1)H NMR and Fourier transform infrared (FT-IR) spectroscopy in combination with ab initio calculations using Gaussian software. The results showed that EG-TBAB DESs can absorb low concentrations of SO(2) and NO(2) from the flue gas simultaneously at low temperatures (≤50 °C). (1)H NMR, FT-IR, and simulation results indicate that SO(2) and NO(2) are absorbed by forming EG-TBAB-SO(2)–NO(2) complexes, Br(–) is the main active site for NO(2) absorption, and NO(2) is more active in an EG-TBAB-NO(2)–SO(2) complex than SO(2). EG-TBAB DESs exhibit outstanding regeneration capability, and absorption capacities remain unchanged after five absorption–desorption cycles. The fundamental understanding of simultaneous capture of SO(2) and NO(2) from this study enables DES structures to be rationally designed for efficient and low-cost desulfurization and denitrification reagents.