Impact of KOH Activation on Rice Husk Derived Porous Activated Carbon for Carbon Capture at Flue Gas alike Temperatures with High CO2/N2 Selectivity

Metal-free porous activated carbon is an effective alternative to capture CO2 due to its high surface area and textural advantages. In this regard, the present research work explores a suitable method for producing activated porous carbon with a high specific surface area through a two-step reaction involving rice husk and KOH at 600 °C for 1 h to capture CO2. By varying the ratio of rice husk biomass to KOH, the texture and specific surface area of the activated porous carbon has been altered. A high surface area of ∼755 m2/g and a micropore volume of 0.243 cm3/g have been observed in the porous carbon produced with a KOH/biomass weight ratio of 3 (PAC2). Nitrogen contents in PAC1 and PAC2 were approximately 2.27 and 2.71 atom %, respectively. When compared with other materials, PAC2 has the highest CO2 adsorption capability, reaching up to 3.13 mmol/g at 0 °C and 1.55 mmol/g at 50 °C. The isosteric heat of adsorption confirms the presence of both physisorption and chemisorption. The materials turn out to be highly CO2/N2 selective, with the highest selectivity of 131, proving that the samples are potential materials for capturing CO2 from flue gases. These findings unequivocally show that porous activated carbon can be used to make CO2 adsorption efficient, inexpensive, and, more importantly, extremely effective.