Efficient uptake of NH3 by dual active sites NH4SCN-imidazole deep eutectic solvents with low viscosity

Abstract

Development of high-efficient solvents for NH3 capture to improve the quality of atmosphere and ecological environment is a hot research topic. Deep eutectic solvents (DESs) as NH3 absorbents can overcome some problems troubling the traditional NH3 capture process. In this work, NH4SCN was paired with imidazole (Im) DESs to form low viscous DESs with dual active sites for highly efficient NH3 absorption. The effects of absorption temperature, gas flow rate, water content, molar ratio on NH3 absorption performance as well as physical properties of NH4SCN/Im DESs were systematically investigated. The results show that NH4SCN/Im DESs can rapidly capture NH3 with good recycling performance, while the gas flow rate only shortens the absorption time. The NH3 absorption capacity of NH4SCN/Im DESs decreased with increasing temperature and NH4SCN/Im molar ratio. The absorption capacity of NH4SCN/Im (1:2) DES reaches 9.65 mol NH3/kg DESs for atmospheric NH3. Based on 1H NMR and IR spectroscopy analysis, the strong hydrogen bond between protic ammonium cation and NH3 plays the major essence of efficient NH3 capture for NH4SCN/Im DESs.