Computer Analysis of the Effect of Activation Temperature on the Microporous Structure Development of Activated Carbon Derived from Common Polypody.

Mirosław Kwiatkowski,Jarosław Serafin,Beata Michalkiewicz,Andy M Booth

doi:10.3390/ma14112951

Abstract

This paper presents the results of a computer analysis of the effect of activation process temperature on the development of the microporous structure of activated carbon derived from the leaves of common polypody (Polypodium vulgare) via chemical activation with phosphoric acid (H3PO4) at activation temperatures of 700, 800, and 900 °C. An unconventional approach to porous structure analysis, using the new numerical clustering-based adsorption analysis (LBET) method together with the implemented unique gas state equation, was used in this study. The LBET method is based on unique mathematical models that take into account, in addition to surface heterogeneity, the possibility of molecule clusters branching and the geometric and energy limitations of adsorbate cluster formation. It enabled us to determine a set of parameters comprehensively and reliably describing the porous structure of carbon material on the basis of the determined adsorption isotherm. Porous structure analyses using the LBET method were based on nitrogen (N2), carbon dioxide (CO2), and methane (CH4) adsorption isotherms determined for individual activated carbon. The analyses carried out showed the highest CO2 adsorption capacity for activated carbon obtained was at an activation temperature of 900 °C, a value only slightly higher than that obtained for activated carbon prepared at 700 °C, but the values of geometrical parameters determined for these activated carbons showed significant differences. The results of the analyses obtained with the LBET method were also compared with the results of iodine number analysis and the results obtained with the Brunauer–Emmett–Teller (BET), Dubinin–Radushkevich (DR), and quenched solid density functional theory (QSDFT) methods, demonstrating their complementarity.

Highlights

Activated carbons are well-known for being a very good gas and liquid phase adsorbents for a wide variety of organic and inorganic chemicals, resulting in their used or consideration for a wide range of applications
The adsorption capacity and efficiency of activated carbons are significantly influenced by their physicochemical properties, which in turn are dependent on carbon precursor selected and the method of synthesis [1,2,3,4,5,6,7,8,9,10,11]
Industrial production of activated carbons starts with the carbonisation of the raw materials, followed by a physical or chemical activation process, or a combination of these processes

Summary

Introduction

Activated carbons are well-known for being a very good gas and liquid phase adsorbents for a wide variety of organic and inorganic chemicals, resulting in their used or consideration for a wide range of applications. Industrial production of activated carbons starts with the carbonisation of the raw materials, followed by a physical or chemical activation process, or a combination of these processes. Carbonisation is achieved by heating the raw materials without the presence of air or in an inert gas atmosphere [22]. The physical activation process comprises a partial gasification of the carbonisation product at a temperature of 800–1000 ◦C with oxidising agents such as water steam or carbon dioxide; the use of a mixture of these agents is possible [23,24]. The use of oxygen at a temperature below 800 ◦C is possible but is used less frequently

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