Microporous carbon derived from cotton stalk crop-residue across diverse geographical locations as efficient and regenerable CO2 adsorbent with selectivity

Abstract

Six porous carbons (PCs) were prepared via thermochemical methodology from cotton-stalk crop residue, collected from diverse geographical locations in India. Although similar in nature, the precursor collection sites majorly influenced the properties of the generated PCs, possibly due to variations in soil characteristics and fertilizer usage patterns. The microstructures were characterized by a series of analytical data, including FT-IR and Raman Spectra, XRD, TGA, SEM imaging, and in-depth XPS studies. Nitrogen sorption isotherms at 77 K of all PCs revealed well-defined microporosity and high specific surface area, varying from 1706 to 2438 m2/g under similar synthetic conditions. Further, gaseous CO2 adsorption studies showed that the PCs exhibited diverse uptake performances at 1 bar under varied temperatures. The maximum uptake capacity of 6.23 mmol/g (273 K), 3.85 mmol/g (298 K), and 3.28 mmol/g (313 K) defined superior values over contemporary adsorbents. A critical-point drying technique was employed further to enhance the CO2 uptake capacity of these carbons. Importantly, all the carbons revealed moderate to good CO2/N2 separation selectivity at low temperature (~25 at 273 K) that experienced a unique enhancement under elevated temperature, as calculated from ideal adsorbed solution theory. After vacuum regeneration, the activated carbons exhibited stable CO2 adsorption up to five cycles, validating their potential reusability for CO2 capture. Precisely, the cotton stalk crop residue-derived PCs represent one-of-a-kind low cost, eco-friendly, abundant, and scalable absorbents for regenerable CO2 capture with moderate heat of adsorption and selectivity values, with promises of practical usability.