High CO2 absorption of O-carboxymethylchitosan synthesised from chitosan

CO2 absorption by liquid-containing amines to form carbamate and bicarbonates is an effective method of CO2 mitigation from industrial exhausts, but this process is expensive and requires large quantities of amines. Here we modified chitosan, a naturally occurring biopolymer containing NH2 functions, to use it for CO2 absorption in aqueous media. Chitosan was dispersed in 40% aqueous NaOH solution then treated with monochloroacetic acid dissolved in isopropanol, to yield O-carboxymethylchitosan. Results show that the CO2 absorption capacity of O-carboxymethylchitosan is 0.508 g/g, which is higher than the capacity of conventional amines such as 1-aminoamine, 2-methylpropanolamine and methyldiethanol amine, but lower than the capacity of monoethanolamine. A cyclic study showed that O-carboxymethylchitosan is a stable component for CO2 absorption and regeneration.