Highly efficient absorption and separation of NH3 by simple lithium deep eutectic solvents

It remains a challenge in chemical industry to achieve highly efficient and reversible capture of ammonia (NH3) for improving environment and ecology. In this work, new lithium deep eutectic solvents (DESs) by pairing simple lithium salt with various hydrogen bond donors of ethylene glycol (EG), formamid (FM), glycerol (Gly), 1,3-dimethyl-2-imidazolidinone (DMI), and N, N'-dimethylpropyleneurea (DMPU) were conducted. Their physical properties were characterized and NH3 absorption performance were investigated from the parameters of temperature, gas flow rate, molar ratio, different HBAs and HBDs. Results demonstrated that LiCl/EG (1:3) DES possessed fast absorption rate, exceptional NH3 absorption mass ratio of 0.219 g g−1 and high NH3/CO2 selectivity of 389.7 at 303.15 K, exceeding all the reported metallic ILs and IL-based DESs. 1H NMR and FT-IR spectra analysis implied that the excellent performance was originated from the comprehensive interaction of lithium and hydroxyl groups with NH3. Present work will provide useful idea for designing metallic DESs for NH3 separation applications.