An environmentally friendly synthesis method of activated carbons based on subabul (Leucaena leucocephala) sawdust waste for CO2 adsorption

Abstract

A novel micro-mesoporous activated carbon (SBL AC-700) is synthesized from subabul (Leucaena leucocephala) sawdust waste by direct single-stage physical activation at 700 °C for 1 h for carbon capture applications. The synthesized AC is characterized to explore various physiochemical properties like elemental composition, surface morphology and crystallinity, presence of functional groups, surface area, pore size, and pore volume. Additionally, emphasis is given to exploring the thermophysical aspects of the novel AC, the literature regarding which is scarce in the open domain. The CO2 adsorption study is carried out for a 0–1 bar pressure for temperatures ranging from 0 to 75 °C. The analysis revealed that the AC possesses a surface area of 590 m2/g and pore volume and width of 0.27 cm3/g and 1.85 nm, corresponding to a 70% microporosity with a well-developed porous structure. At 25 °C and 1 bar, a CO2 uptake of 40.54 cm3/g is achieved, corresponding to an increment of 6–202% compared to other commercials, chemically and physically activated carbons. Moreover, SBL AC-700 has a thermal conductivity of 0.095 W/m K, 8–131% higher than other benchmarks ACs and much lower specific heat of 0.82 kJ/kg K corresponding to lesser regeneration energy requirements. Experimental data are fitted with various isotherm models, i.e., Langmuir, Freundlich, Sips, R–P, and Toth, out of which R–P and Toth models exhibit the best fit. In continuation, adsorption kinetics is studied to explore the dynamic performance of the SBL AC-700 by using Pseudo-first-order, Pseudo-second-order, Elovich, and intraparticle diffusion kinetic models.