Synthesis and Characterization of Activated Biocarbons Produced from Avocado Seeds Using the Non-Toxic and Environmentally Friendly Activating Agent K2CO3 for CO2 Capture

Activated biocarbons were synthesized from avocado seeds using potassium carbonate as an activating agent. The study aimed to evaluate K₂CO₃ as a greener and less corrosive alternative to KOH, traditionally used for producing porous carbons. Twelve samples were obtained under varying activation conditions using both dry K₂CO₃ and its saturated solution. The material activated at 800 °C with a 1:1 precursor-to-activator ratio (C_K₂CO₃_800) showed the highest CO₂ adsorption capacity of 6.26 mmol/g at 0 °C and 1 bar. Nitrogen adsorption-desorption analysis confirmed a predominantly microporous structure, with ultramicropores (0.3-0.7 nm) primarily responsible for the high CO₂ uptake. The Sips model provided the best fit to the adsorption equilibrium data, indicating a heterogeneous surface. The isosteric heat of adsorption (22-26 kJ/mol) confirmed a physical adsorption mechanism. Furthermore, the CO₂/N₂ selectivity, evaluated using the Ideal Adsorbed Solution Theory (IAST), reached values up to 18 at low pressures, highlighting the excellent separation performance. These findings demonstrate that avocado seed-derived activated carbons prepared with K₂CO₃ are efficient, renewable, and environmentally friendly sorbents for CO₂ capture, combining high adsorption capacity with sustainability and ease of synthesis.