Synthesis of Activated Carbons by Thermal Treatments of Agricultural Wastes for CO2 Capture from Flue Gas

Activated carbons (AC) were synthesized by a pyrolysis process and activation with water vapor of agricultural wastes, namely, apricot stones, peach stones, and olive stones, for CO2 capture from a simulated flue gas. Kinetic and thermodynamic adsorption tests were carried out in a lab-scale fixed-bed column under operating conditions typical of a flue gas (i.e., P = 1 atm, CO2 = 3-30%, T = 30 degrees C). Experimental results showed that the AC derived from olive stones is characterized by a slightly faster saturation, due to a higher contribution of meso-macropores, while the AC derived from the apricot stones had the highest adsorption capacity, likely ascribed to a higher micropore volume and a narrower pore size distribution. Regeneration studies conducted on the AC derived from apricot stones showed that CO2 adsorption is a reversible process and that the time to achieve a desired CO2 recovery percentage is mainly controlled by temperature and, at less extent, by desorbing agent flow rate.