Vol.:(0123456789) 1 3 Journal of Thermal Analysis and Calorimetry https://doi.org/10.1007/s10973-021-10943-8 Calorimetric evaluation of activated carbons prepared by chemical activation Sergio Acevedo 1  · Liliana Giraldo 1  · Juan Carlos Moreno‑Piraján 2 Received: 1 December 2020 / Accepted: 7 June 2021 © Akadémiai Kiadó, Budapest, Hungary 2021 Abstract In this research, a calorimetric evaluation of activated carbon-type adsorbent solids prepared by chemical activation of Afri- can palm shells with solutions of Fe(NO 3 ) 3 and Cu (NO 3 ) 2 salts with change in concentration was carried out. In the investiga- tion, the immersion calorimetry in porous carbon-type solids in water, dichloromethane, and benzene was determined. The solids were characterized by the nitrogen adsorption technique at 77 K and the determination of functional groups by Boehm titrations. The calorimetric evaluation showed that the immersion of porous materials generated immersion enthalpy values between −10.8 and −131 J g −1 . The immersion calorimetry of these materials in the immersion liquids varied with respect to the change of chemical agents and to the change of concentrations at which these materials were prepared, showing varia- tions in textural and chemical characteristics of porous solids. The BET areas obtained are between 120 and 1360 m 2  g −1 , and pore volumes are between 0.05 and 0.51 cm 3  g −1 ; these parameters increased proportionally to the increase in the values of immersion enthalpies. The adsorbent solids obtained are used in the adsorption of CO 2 , in this investigation, the calorimetric study was carried out in solvents with diferent polarities, in order to correlate these enthalpic properties of the activated carbons with the surface area and the adsorption, which presented values between 88 and 218 mg g −1 . Keywords Activated carbon · Chemical activation · Immersion enthalpy · Hydrophobic factor Introduction The use of lignocellulosic residues of agroindustry origin as precursors in the preparation of activated carbons is well known and even more so if they are produced in high quanti- ties. In this research, the African palm shells were chosen as precursor material in the preparation of adsorbent solids, since Colombia is currently among the top producing coun- tries of this plant, with more than 3 million tons of shells per year. These are solid residues from the production of palm oil that currently causes environmental pollution due to the lack of adequate alternatives that lead to its use in industrial processes and thus giving added value to this residue. The preparation of activated carbon is associated with the retention of pollutants in aqueous media and at atmos- pheric level, since industrialization requires more technical processes and more rigorous legislation regarding emissions in most countries. Activated carbon is prepared in diferent forms; the one chosen for this study is the granular one, which allows its use on an industrial scale. With the chemi- cal impregnation, the intention was to modify the surface chemistry of the adsorbent material in order to develop selectivity and afnity in CO 2 capture [1]. The immersion calorimetry technique is relevant due to its usefulness in the characterization of solids and in the study of diferent interactions between molecules and the surface of the (AC); this technique is thermodynamic in nature, since it provides data on the interactions between adsorbent materials and the diferent wetting liquids in the immersion; this generates a certain amount of heat, which correlates the accessible area with the interactions that occur between the surface of the material and immersion liquid under study. The intensity of the thermal efect generates a * Juan Carlos Moreno-Piraján jumoreno@uniandes.edu.co 1 Departamento de Química, Facultad de Ciencias, Universidad Nacional de Colombia, Carrera 30 No 45-03, Bogotá, DC, Colombia 2 Departamento de Química, Grupo de Investigación en Sólidos Porosos y Calorimetría, Facultad de Ciencias, Universidad de Los Andes, Carrera 1a No 18 A -12, Bogotá, DC, Colombia