Abstract
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.
Highlights
The quality of the air that is breathed in almost the entire planet is being significantly affected by atmospheric pollutants present in daily anthropic activities, to which the supply and use of fossil fuels contributes approximately to 80% of the emissions of Greenhouse gases such as: carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O)
Different international organizations have determined, that in order to reduce the impact that this situation has on living beings, ecosystems and sustainable development, it is necessary that the global temperature rise keeps below 1.5◦C, mechanisms that allow the reduction of carbon dioxide and other greenhouse gas emissions in all sectors of society are needed (Rubino et al, 2019; World Meteorological Organization (WMO), 2019)
The precursor was chemically activated using two chemical agents mixed at different concentrations: CaCl2 and H3PO4, subsequently carbonized and the porous material obtained was chemically modified with HNO3 and NH4OH in order to enrich the surface chemistry of the solid with functional groups that increase its interaction with the CO2 molecule
Summary
The quality of the air that is breathed in almost the entire planet is being significantly affected by atmospheric pollutants present in daily anthropic activities, to which the supply and use of fossil fuels contributes approximately to 80% of the emissions of Greenhouse gases such as: carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). Technological options for CO2 capture have been studied, such as: chemical absorption, cryogenic separation, use of separation membranes, carbonationcalcination cycles and adsorption (Yu et al, 2012; Wang et al, 2017; Borhani and Wang, 2019). It has been shown that studies aimed at the preparation and use of activated carbon for CO2 removal have increased in recent years, because this adsorbent material has a developed porous structure, a varied surface chemistry, a wide surface area, specificity, among other features that can be adjusted according to the needs of the application. The precursor was chemically activated using two chemical agents mixed at different concentrations: CaCl2 and H3PO4, subsequently carbonized and the porous material obtained was chemically modified with HNO3 and NH4OH in order to enrich the surface chemistry of the solid with functional groups that increase its interaction with the CO2 molecule. CO2 adsorption calorimetry was performed to determine energy aspects of the process
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