Enhancing CO2 capture performance through activation of olive pomace biochar: A comparative study of physical and chemical methods

This work contributes understanding technical feasibility use of an agro-industrial waste as raw material for CO2 capture. Physical and chemical activation treatments to enhance adsorption properties of exhausts olive pomace biochar were investigated. Innovatively, the effects of different kinds of activating agents (steam, CO2, H3PO4 and KOH) on activated biocarbon's properties were deeply examined, also through an original high-pressure thermobalance, that is enabled higher initial sample weights, temperatures, and pressures compared to those employed in conventional methods. The activation conditions significantly affect the biochar morphology and CO2 adsorption capacity. Chemical activation, particularly with KOH, produced highly microporous structures, greatly enhancing CO2 adsorption. Specifically, KOH activation achieved adsorption capacities of up to 3.04 mmol/g at 30 ◦C and 10 bar. Textural analysis showed that KOH activation primarily increased microporosity, while other methods produced both micropores and mesopores. Interestingly, acid and physical activations were less effective, as they reduced CO2 adsorption due to changes in the internal structure. Thus, olive pomace proves to be a promising precursor for developing efficient biochar adsorbents. The use of KOH as an activating agent particularly stands out, achieving notable CO2 adsorption capacities.