Abstract
In this study, the preparation of activated carbons from various materials of biomass origin by activation with potassium hydroxide and a comprehensive computer analysis of their porous structure and adsorption properties based on benzene (C6H6) adsorption isotherms were carried out. In particular, the influence of the mass ratio of the activator’s dry mass to the char mass on the formation of the microporous structure of the obtained activated carbons was analysed. The summary of the analyses carried out based on benzene adsorption isotherms begged the conclusion that activated carbon with a maximum adsorption volume in the first adsorbed layer and homogeneous surface can be obtained from ebony wood at a mass ratio of the activator to the char of R = 3. The obtained results confirmed the superiority of the new numerical-clustering-based adsorption analysis (LBET) method over simple methods of porous structure analysis, such as the Brunauer–Emmett–Teller (BET) and Dubinin–Raduskevich (DR) methods. The LBET method is particularly useful in the evaluation of the influence of the methods and conditions of production of activated carbons on the formation of their porous structure. This method, together with an appropriate economic analysis, can help in the precise selection of methods and conditions for the process of obtaining activated carbons at specific manufacturing costs, and thus makes it possible to obtain materials that can successfully compete with those of other technologies used in industrial practice and everyday life.
Highlights
Published: 23 July 2021Activated carbons are amorphous carbonaceous materials characterized by a large specific surface area and adsorption capacity
Based on the SEM-EDX research, which was conducted for both the primary raw materials and the activated carbons derived from them presented in Table 2, it is correct to conclude that the highest content of C and O was found in pecan nut shells and the PNAC/3 activated carbons, which were obtained from pecan nut shells
In comparison with the activated carbons obtained from wood, one can see the isotropic structure and a significantly smaller proportion of voids between the walls, as well as the smaller diameters of the voids resulting from the much denser structures of the nut shells
Summary
Activated carbons are amorphous carbonaceous materials characterized by a large specific surface area and adsorption capacity. At an early stage of carbonisation, e.g., at about 300–350 ◦ C, the less durable links in the polymeric network break up, and free macromolecules are formed. Substantial amounts of volatile components are discharged, and the atoms of carbon are regrouped into a more stable form [3,4]. Cross-links between the macromolecules are generated, and the stiff, network-like carbonaceous structure that develops in the process reflects the development of the microporosity of the material. When the carbonisation temperature exceeds 500 ◦ C, the structure becomes increasingly carbonised and aromatised as a result of the elimination of the atoms of hydrogen and oxygen [3,4]
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