Influence of the activation route on the textural properties and CO2 capture performance of activated carbons derived from Parkinsonia aculeata
Gomez-Delgado, Edward (1); Rodríguez Ortíz, Hector (1); Nunell, Gisel (1); Alvarez-Zurita, Carlos (1); Gómez Vargas, Carolina (1); Cukierman, Ana Lea (1 y 2); Bonelli, Pablo Ricardo (1).
(1) Instituto de Tecnología de Alimentos y Procesos Químicos ITAPROQ CONICET. Universidad de Buenos Aires, FCEyN, Depto. de Industrias, Int. Güiraldes 2620, Ciudad Universitaria. Buenos Aires, Argentina. (2) Universidad de Buenos Aires, FFyB, Depto. de Tecnología Farmacéutica, Cátedra de Tecnología Farmacéutica II. Junín 956. Buenos Aires, Argentina.
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Abstract
The continuous increase in anthropogenic CO2 emissions has driven the development of efficient adsorbent materials derived from residual biomass. In this study, the influence of two activation routes on the textural properties and CO2 adsorption capacity of activated carbons (ACs) produced from Parkinsonia aculeata was evaluated. For the conventional route (CA_PA-C), the biomass was carbonized at 300 °C for 1 h in air. Subsequently, the resulting biochar was impregnated with KOH at a biochar mass ratio of 1:1 and thermally activated at 800 °C for 2 h under a nitrogen atmosphere. In contrast, for the microwave-assisted route (CA_PA-M), the precursor was carbonized at 500 °C for 1 h, and the resulting biochar was impregnated with KOH at a 1:3 mass ratio and subsequently subjected to microwave irradiation at 850 W and 2.45 GHz for 2 min. The resulting materials were characterized by N2 adsorption isotherms at 77 K and CO2 adsorption isotherms at 273 K. CA_PA-M exhibited a greater overall textural development, reaching a BET specific surface area of 1011 m2/g, a total pore volume of 0.51 cm3/g, and an N2 adsorption capacity of 14.42 mmol/g. In comparison, CA_PA-C exhibited a BET surface area of 768 m2/g, a total pore volume of 0.37 cm3/g, and an N2 adsorption capacity of 11.89 mmol/g. However, this trend was not reflected in the CO2 capture performance. CA_PA-C showed a higher CO2 adsorption capacity, reaching 5.01 mmol/g compared with 4.74 mmol/g for CA_PA-M. These findings demonstrate that a larger specific surface area does not necessarily result in enhanced CO2 capture, suggesting that the distribution, size, and accessibility of ultramicropores play a determining role in the adsorption process. Therefore, the specific conditions associated with each activation route significantly influenced both the porous structure and the CO2 adsorption performance of the resulting activated carbons.
Keywords: CO2 adsorption; microwave-assisted activation; microporosity.