An analysis of the effect of the additional activation process on the formation of the porous structure and pore size distribution of the commercial activated carbon WG-12

Recent Developments in Activated Carbon Catalysts Based on Pore Size Regulation in the Application of Catalytic Ozonation

Due to its highly developed pore structure and large specific surface area, activated carbon is often used as a catalyst or catalyst carrier in catalytic ozonation. Although the pore structure of activated carbon plays a significant role in the treatment of wastewater and the mass transfer of ozone molecules, the effect is complicated and unclear. Because different application scenarios require catalysts with different pore structures, catalysts with appropriate pore structure characteristics should be developed. In this review, we systematically summarized the current adjustment methods for the pore structure of activated carbon, including raw material, carbonization, activation, modification, and loading. Then, based on the brief introduction of the application of activated carbon in catalytic ozonation, the effects of pore structure on catalytic ozonation and mass transfer are reviewed. Furthermore, we proposed that the effect of pore structure is mainly to provide catalytic active sites, promote free radical generation, and reduce mass transfer resistance. Therefore, large external surface area and reasonable pore size distribution are conducive to catalytic ozonation and mass transfer.

Commercial Kevlar derived activated carbons for CO2 and C2H4 sorption

The carbonaceous precursor was obtained via pyrolysis of commercial aramid polymer (Kevlar). Additionally the precursor was activated at 1000°C in CO2 atmosphere for different times. Obtained materials were characterised by BET; XPS; SEM and optical microscopy. The sorption capacities were determined by temperature swing adsorption performed in TGA apparatus for CO2 and C2H4 gases. The obtained materials exhibit high difference in sorption of these gases i.e. 1.5 and 2.8 mmol/g @30°C respectively and high SSA ~1600 m2/g what can be applied in separation applications. The highest uptakes were 1.8 and 3.1 mmol/g @30°C respectively. It was found that the presence of oxygen and nitrogen functional groups enhances C2H4/CO2 uptake ratio.

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

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.

An Evaluation of the Reliability of the Results Obtained by the LBET, QSDFT, BET, and DR Methods for the Analysis of the Porous Structure of Activated Carbons

This paper presents the results of an analysis of the impact of the activator to the product of carbonized materials mass ratio on the porous structure of activated carbons prepared from mahogany, ebony, and hornbeam wood by carbonization and chemical activation with potassium hydroxide. The analyses were carried out on nitrogen adsorption isotherms using the Brunauer–Emmett–Teller (BET), Dubinin-Radushkevitch (DR), and Quenched Solid Density Functional Theory (QSDFT) methods, as well as the numerical clustering-based adsorption analysis (LBET) method. The activated carbons with the best adsorption properties and homogeneous surfaces were prepared at a mass ratio of R = 3. The analyses suggest the significant potential of producing adsorbents characterized by a large surface area and adsorptive capacity from raw materials such as mahogany, ebony, and hornbeam wood. The analyses in question also included an evaluation of the usability and reliability of the results obtained with the employed methods of structural analysis. Particular focus was placed on the limitations of adsorption models and on critically analyzing the output data. Our study shows the unique advantages of the LBET method compared to the other methods used. The LBET method allowed us, for example, to determine the degree of heterogeneity of the surface of the studied activated carbons and the shape of the clusters of adsorbate molecules formed in the pores of the studied material, as well as obtain information about the distribution of adsorption energy on the first adsorbed layer. This study also demonstrates the limitations of the methods used and the necessity to use LBET and QSDFT methods simultaneously for porous structural analysis. The simultaneous analysis of the adsorption isotherms via the LBET and the QSDFT methods makes it possible to choose the optimal preparation conditions while considering the properties of the original raw material. The analyses also suggest the complementary character of the employed methods and the scope of the useful and reliable information that can be obtained with these methods.

Activated carbons from common nettle as potential adsorbents for CO2 capture

Activated carbons (ACs) prepared from common nettle (Urtica Dioica L.) were studied in terms of carbon dioxide adsorption. ACs were prepared by KOH chemical activation in a nitrogen atmosphere at temperatures (ranging from 500 to 850°C). The pore structure and the surface characterization of the ACs were specified based on adsorption-desorption isotherms of nitrogen measured at –196°C and carbon dioxide at 0°C. The specific surface area was calculated according to the BET equation. The pore volume was estimated using the DFT method. The highest values of the specific surface area (SSA) showed activated carbons produced at higher carbonization temperatures. All samples revealed presence of micropores and mesopores with a diameter range of 0.3–10 nm. The highest value of the CO2 adsorption, 4.22 mmol/g, was found for the material activated at 700°C.

Preparation of Activated Carbon from the Biodegradable film for Co2 Capture Applications

In this work for the fi rst time, activated carbons were prepared from carboxymethyl fi lm (low-cost carboxymethyl fi lm waste), using chemical activation with potassium hydroxide. The samples were characterized by nitrogen adsorption-desorption at 77 K, XRD, SEM methods. The high values of the specifi c surface area and total pore volume were achieved and were equal to 2064 m2/g and 1.188 cm3/g, respectively. Waste from the fi lm can be immediately utilized without CO2 production. This is the environmentally friendly way of waste utilization. Through this process, we can protect our environment. This study showed that the activated carbon obtained from carboxymethyl fi lm waste can be used as a good adsorbent for CO2 adsorption.

An evaluation of the reliability of the characterization of the porous structure of activated carbons based on incomplete nitrogen adsorption isotherms

The paper presents the results of research devoted to reliability evaluation of the analysis of results of the porous structure of activated carbons based on incomplete nitrogen adsorption isotherms using the BET, t-plot, and NLDFT methods, as well as the LBET method comprising the unique numerical fast multivariant procedure of adsorption system identification. The research involved the application of the nitrogen adsorption isotherms obtained for five samples of activated carbons produced from waste materials of organic origin by way of chemical activation with potassium hydroxide, sodium hydroxide, and potassium carbonate with the use of microwave heating. The analyses performed pointed to a good correlation between the results obtained using the BET, t-plot, NLDFT, and LBET methods. Moreover, the parameters of the porous structure determined using these methods based on incomplete adsorption isotherms of nitrogen are in fact as reliable as these methods allow.

Utilization of spent dregs for the production of activated carbon for CO2 adsorption

The objective of this work was preparation of activated carbon from spent dregs for carbon dioxide adsorption. A saturated solution of KOH was used as an activating agent. Samples were carbonized in the furnace at the temperature of 550°C. Textural properties of activated carbons were obtained based on the adsorption-desorption isotherms of nitrogen at −196°C and carbon dioxide at 0°C. The specific surface areas of activated carbons were calculated by the Brunauer – Emmett – Teller equation. The volumes of micropores were obtained by density functional theory method. The highest CO2 adsorption was 9.54 mmol/cm3 at 0°C – and 8.50 mmol/cm3 at 25°C.

Activated carbons prepared from hazelnut shells, walnut shells and peanut shells for high CO2 adsorption

Research treats about producing activated carbons for CO2 capture from hazelnut shells (HN), walnut shells (WN) and peanut shells (PN). Saturated solution of KOH was used as an activating agent in ratio 1:1. Samples were carbonized in the furnace in the range of temperatures 600°C–900°C. Properties of carbons were tested by N2 adsorption method, using BET equation, DFT method and volumetric CO2 adsorption method. With the increase of carbonization temperature specific surface area of studied samples increased. The largest surface area was calculated for samples carbonized at 900°C and the highest values of CO2 adsorption had samples: PN900 at 0°C (5.5 mmol/g) and WN900 at 25°C (4.34 mmol/g). All of the samples had a well-developed microporous structure.

Adsorption of carbon dioxide on TEPA-modified TiO2/titanate composite nanorods

CO₂was successfully chemisorbed/physisorbed on a TiO₂/titanate composite nanorod functionalized with TEPA amine.