Valorization of shrimp shell biowaste for environmental remediation: Efficient contender for CO₂ adsorption and separation

Over the years, single heteroatom-doped biowaste-derived activated carbons were studied for effective CO₂ adsorption. However, binary or ternary heteroatoms-doping is equally important and could significantly affect the CO₂ adsorption and flue gas (i.e., CO₂/N₂) separation. Herein, for the first time, shrimp shell-derived chitosan was used to design a series of ternary (N, S, O)-doped hierarchically porous carbons. The resultant carbons exhibit a large specific surface area (up to 2095 m²/g), micropore volume (up to 1.2647 cm³/g), and high heteroatoms content i.e., N up to 4.1 at. %, S up to 4.6 at. %, and O up to 13.4 at. %. Consequently, high CO₂ uptake of 236.80 mg/g at 273 K/1 bar and an excellent CO₂/N₂ gas selectivity (84.3) was observed, attributed to the synergistic role of narrow micropores (<1 nm) and optimum heteroatom content. Furthermore, the stable CO₂ adsorption-desorption cyclic behavior under flue gas conditions i.e., 15% CO₂/85% N₂ reveals the physisorption mechanism of CO₂ adsorption and appears to be an energy-efficient regeneration process. Concluding, our work demonstrates a facile route of valorization of biowaste for environmental remediation to combat biowaste accumulation and mitigating atmospheric CO₂ levels, simultaneously.