From biopolymer dissolution to CO2 capture under atmospheric pressure - A molecular view on biopolymer@Ionic liquid materials

Abstract

Finding a cheap and easily recycling material that can capture CO2 under atmospheric pressure (1 atm) is of paramount importance. In this context, combining ionic liquids (ILs) with abundant and natural materials, such as chitin-based biopolymers, appears as an interesting alternative. In this work, four acetate-based ILs were selected to explore the solubility of chitin, chitosan, and carboxymethyl-chitosan. Using carboxymethyl-chitosan and biopolymer monomer units as models, different Nuclear Magnetic Resonance (NMR) techniques, namely, 1H, 13C, nuclear Overhauser effect spectroscopy, and spin-lattice relaxation, were performed to evaluate the dissolution. Shrimp shells were used as a chitin source. Through a simple acid/base treatment, it was possible to remove minerals and proteins, and use it to prepare biopolymer@IL materials for CO2 capture tests. Efficient CO2 sorption capacity was observed upon bubbling CO2 with a maximum of 2.32 mmolCO2/gsorbent. Under N2 bubbling, the system demonstrated excellent recycling capacity using a room temperature procedure that outperformed aqueous amine solutions recycling. The absence of heating and vacuum recycling procedures, combined with the use of N2 or compressed air is much more appealing for industrial applications.