Ionic liquid-grafted chitosan/polyethylene glycol blended membranes for efficient separation of H2S

Chitosan (CS) is a potential membrane material for acid gas separation owing to its advantages of low cost, high biocompatibility, good film-forming property, and abundant amine groups. However, due to the strong hydrogen bonding network inside bulky CS, it has poor solvent processability and high membrane crystallinity leading to slow gas permeation. Herein, via alkylating primary amine on chitosan using 1-bromohexyl-3-methylimidazolium bromide ([Brhmim]Br), water-processable ionic liquid-grafted chitosan (ICS) membrane was fabricated for H 2 S separation. Furthermore, polyethylene glycol (PEG) was introduced into ICS to improve H 2 S separation performance owing to its good plasticizing ability and highly reversible hydrogen bonding interaction with H 2 S. The successful fabrication of ICS and ICS/PEG membranes was validated using various characterizations. Notably, H 2 S/CO 2 /CH 4 (20/20/60 vol%) mixed gas permeation test shows H 2 S permeability up to ∼1100 Barrer, with desired H 2 S/CH 4 (∼24) and H 2 S/CO 2 (∼11) selectivity obtained. Quantum chemical calculations revealed that both the ionic liquid and PEG have highly reversible hydrogen bonding interaction with H 2 S, which facilitates H 2 S permeation. Overall, this work proposes a novel and green method for preparing modified chitosan membranes targeting H 2 S separation, which may provide a new insight into the design of sustainable membrane materials for natural gas desulfurization.