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.