Deep eutectic solvent-based blended membranes for ultra-super selective separation of SO.

SO is a major atmospheric pollutant leading to acid rain and smog. As a new generation of green solvents, deep eutectic solvents (DESs) have been widely investigated for gas capture. Nevertheless, studies on DES-based membranes for SO separation are yet minimal. Herein, we devised polymer/DES blended membranes comprising 1-butyl-3-methyl-imidazolium bromide ([Bmim]Br)/diethylene glycol (DEG) DES and poly (vinylidene fluoride) (PVDF), and these membranes were firstly used for selective separation of SO from N and CO. The permeability of SO reaches up to 17480 Barrer (0.20 bar, 40 ºC) in PVDF/DES blended membrane containing 50 wt% of [Bmim]Br/DEG (2:1), with ultrahigh SO/N and SO/CO selectivity of 3690 and 211 obtained, respectively, far exceeding those in the state-of-the-art membranes reported in literature. The highly-reversible multi-site interaction between SO and [Bmim]Br/DEG DES was revealed by spectroscopic analysis. Furthermore, the PVDF/DES blended membrane was also able to efficiently and stably separate SO/CO/N (2.5/15/82.5%) mixed gas for at least 100 h. This work demonstrates for the first time that [Bmim]Br-based DESs are very efficient media for membrane separation of SO. The easy preparation, low cost and high performance enable polymer/DES blended membranes to be promising candidates for flue gas desulfurization.