Study of CO₂ Adsorption on Chemically Modified Activated Carbon With Nitric Acid and Ammonium Aqueous

The study of CO₂ adsorption on adsorbent materials is a current topic of research interest. Although in real operating circumstances, the removal conditions of this gas is carried out at temperatures between 290 and 303 K and 1 Bar of pressure or high pressures, it is useful, as a preliminary approach, to determine CO₂ adsorption capacity at 273K and 1 Bar and perform a thermodynamic study of the CO₂ adsorption heats on carbonaceous materials prepared by chemical activation from African palm shell with CaCl₂ and H₃PO₄ solutions, later modified with HNO₃ and NH₄OH, with the aim to establish the influence that these treatments have on the textural and chemical properties of the activated carbons and their relationship with the CO₂ adsorption capacity. The carbonaceous materials were characterized by physical adsorption of N₂ at 77K, CO₂ at 273K, proximate analysis, Boehm titrations and immersion calorimetry in water and benzene. Activated carbons had a BET area between 634 and 865 m²g^-1, with a micropore volume between 0.25 and 0.34 cm³g^-1. The experimental results indicated that the modification of activated carbon with HNO₃ and NH₄OH generated a decrease in the surface area and pore volume of the material, as well as an increase in surface groups that favored the adsorption of CO₂, which was evidenced by an increase in the adsorption capacity and the heat of adsorption.