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

Abstract

• Fe(II)EG-ChCl DESs demonstrated an excellent capacity to adsorb NO. • The denitrification performance of Fe(II)EG-ChCl DESs was optimized. • Fe(II) EG-ChCl DESs maintained a first-order absorption reaction kinetics. • Fe(II) was found to be the main absorptive active species. 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 (FeCl 2 ), 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 × 10 6 (L/mol·s) for the denitrification reaction. The FT-IR result indicated that there was a chemical interaction between Fe 2+ and NO, and Fe 2+ was the absorptive active species.