Absorption mechanism and kinetics of NO by Fe(II) based ethylene glycol (EG)-choline chloride (ChCl) deep eutectic solvents

A series of novel iron-based deep eutectic solvents (DESs) as denitrification sorbents were evaluated to capture NO from simulated flue gases. The application of Fe(II) EG-ChCl DESs demonstrated the efficiency of absorption performance with the complete removal of NO and zero secondary pollution. In this study, mixtures of Ferric chloride (FeCl2), Ethylene glycol (EG), and Choline chloride (ChCl) were prepared using Fe(II) EG-ChCl DESs. Experimental results showed that the best performance for denitrification was achieved when DES solutions were treated at 60 °C, the gas flow rate of 50 mL/min, 5% partial pressure of steam, and the concentration of Fe(II) was 0.1 mol/L. Furthermore, excellent stability for denitrification was observed for the Fe(II) EG-ChCl DESs during five absorption–desorption cycles. The absorption reaction of Fe(II) EG-ChCl DESs maintained a first-order reaction kinetics with a reaction rate constant of 1.1 × 106 (L/mol·s) for the denitrification reaction. The FT-IR result indicated that there was a chemical interaction between Fe2+ and NO, and Fe2+ was the absorptive active species.