Activated carbons are porous materials of great importance for several processes. Among the main applications of activated carbons is their use in the adsorption of pollutants in gaseous phase1 or liquid phase,2 gases storage3 and as catalysts support.4 Porous materials such as activated carbons are usually characterized by several physical parameters such as surface area and pore volume. In the development of these materials it is very important to satisfy such physical properties, because they will directly influence the performance of the material in its application.https://www.coalactivatedcarbon.com/
The surface areas of activated carbons are usually measured using the Brunauer-Emmett-Teller (BET) method,6 which employs the nitrogen adsorption at different pressures at the temperature of liquid nitrogen (77 K). The surface area according to BET is then determined by the product of the cross-sectional area of the nitrogen molecule, of the Avogadro’s number and of the specific monolayer capacity of nitrogen, which is obtained by an equation proposed by BET with further modifications. For the pore volume determination, the procedure more commonly used also uses nitrogen adsorption isotherm data. The total pore volume is estimated from the amount of nitrogen adsorbed at the highest relative pressure and the micropore volume is calculated from the nitrogen adsorption isotherms using the Dubinin-Radushkevich equation.7 In spite of these methods being more used and employed as a reference in the surface area and pore volume determination of porous materials, they are time consuming and require the use of expensive equipment.
Additional information about the structure of activated carbons can be obtained by the adsorption characteristics of different adsorbates, such as methylene blue and iodine. Adsorption experiments of these molecules are easy and habitually done to characterize activated carbons with the purpose of obtaining information on the adsorption capacity of the materials. According to the dimensions of the methylene blue molecule, it is mainly adsorbed in mesopores, however, a small portion is also found in larger micropores. In relation to methylene blue, the iodine molecule possesses inferior dimensions which make its penetration in micropores possible.5 These charac-teristics confer such molecules the potential for using them as probes in the study of the physical structure of activated carbons. In spite of this, no detailed study has been found concerning the quantitative relationships between methylene blue and iodine numbers and the structural characteristics of the activated carbons.https://www.activated-carbon-pellets.com/
The surface areas of activated carbons are usually measured using the Brunauer-Emmett-Teller (BET) method,6 which employs the nitrogen adsorption at different pressures at the temperature of liquid nitrogen (77 K). The surface area according to BET is then determined by the product of the cross-sectional area of the nitrogen molecule, of the Avogadro’s number and of the specific monolayer capacity of nitrogen, which is obtained by an equation proposed by BET with further modifications. For the pore volume determination, the procedure more commonly used also uses nitrogen adsorption isotherm data. The total pore volume is estimated from the amount of nitrogen adsorbed at the highest relative pressure and the micropore volume is calculated from the nitrogen adsorption isotherms using the Dubinin-Radushkevich equation.7 In spite of these methods being more used and employed as a reference in the surface area and pore volume determination of porous materials, they are time consuming and require the use of expensive equipment.
Additional information about the structure of activated carbons can be obtained by the adsorption characteristics of different adsorbates, such as methylene blue and iodine. Adsorption experiments of these molecules are easy and habitually done to characterize activated carbons with the purpose of obtaining information on the adsorption capacity of the materials. According to the dimensions of the methylene blue molecule, it is mainly adsorbed in mesopores, however, a small portion is also found in larger micropores. In relation to methylene blue, the iodine molecule possesses inferior dimensions which make its penetration in micropores possible.5 These charac-teristics confer such molecules the potential for using them as probes in the study of the physical structure of activated carbons. In spite of this, no detailed study has been found concerning the quantitative relationships between methylene blue and iodine numbers and the structural characteristics of the activated carbons.https://www.activated-carbon-pellets.com/
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