Diana P. Vargas

CO2 Adsorption on Activated Carbon Honeycomb-Monoliths: A Comparison of Langmuir and Tóth Models

Activated carbon honeycomb-monoliths with different textural properties were prepared by chemical activation of African palm shells with H3PO4, ZnCl2 and CaCl2 aqueous solutions of various concentrations. The adsorbents obtained were characterized by N2 adsorption at 77 K, and their carbon dioxide adsorption capacities were measured at 273 K and 1 Bar in volumetric adsorption equipment. The experimental adsorption isotherms were fitted to Langmuir and Tóth models, and a better fit was observed to Tóth equation with a correlation coefficient of 0.999. The maximum experimental values for adsorption capacity at the highest pressure (2.627–5.756 mmol·g−1) are between the calculated data in the two models.

Relación entre la entalpía de inmersión de monolitos de carbon activado y parametros texturales

In this study, Disc and honeycomb-shaped activated carbon monoliths were obtained using as a precursor coconut shell, without the use of any binder. Textural characterization was performed by adsorption of N2 at 77 K and immersion calorimetry into benzene. The experimental results showed that the activation with zinc chloride produces a wide development of micropores, yielding micropore volumes between 0,38 and 0,79 cm3 g-1, apparent BET surface area between 725 and 1523 m2 g-1 and immersion enthalpy between 73,5 and 164,2 J g-1.Were made comparisons between textural parameters and energy characteristics.

Preparation and Characterization of Textural and Energetic Parameters of Common and Functionalized SBA-15 Mesoporous Silicas

A set of SBA-15 ordered mesoporous silicas presenting different surface acidities was obtained by organo-functionalization. Amino and sulphonic groups were attached onto the silica surface in order to determine the influence of organo-functionalization with acidic and basic moieties on the adsorption properties of silica. Cephalexin, an antibiotic molecule characterized by its zwitterionic nature, was selected as the adsorbate. The obtained matrices were characterized by scanning electron microscopy, energy dispersive X-ray analysis and nitrogen adsorption isotherms at 77 K. Enthalpies of immersion into water, benzene and cephalexin solutions were measured by immersion calorimetry, and the cephalexin adsorption capacities of the different matrices were also determined. The structure of SBA-15 was conserved in the functionalized samples despite a noticeable reduction in the BET surface area, pore volume and pore size. It was found that the inclusion of amino groups promoted interaction between the adsorbent and adsorbate, thereby favouring the retention of cephalexin.

Determination of Energy Characteristic and Microporous Volume by Immersion Calorimetry in Carbon Monoliths

Activated carbon monoliths disc and honeycomb type were prepared by chemical activation of coconut shell with zinc chloride at different concentrations, without using a binder. The structures were characterized by N2 adsorption at 77 K and immersion calorimetry into benzene. The experimental results showed that the activation with zinc chloride produces a wide microporous development, with micropore volume between 0,38 and 0,79 cm3g-1, apparent BET surface area between 725 and 1523 m2g-1 and immersion enthalpy between 73,5 and 164,2 Jg-1. We compared the experimental enthalpy with calculated enthalpy by equation Stoeckli-Kraehenbuehl finding a data dispersion from which can infer that the structures are not purely microporous; this fact is ratified with similar behavior that the evidence t the product EoWo.

Activated Carbon for CO2 Adsorption Obtained through the Chemical Activation of African Palm Stone

In this study, activated carbons were prepared and tested as CO2 adsorbents at a temperature of 273 K and at atmospheric pressure. African palm stone was used as the precursor material, which was initially impregnated with CaCl2 solutions at different concentrations. The textural characterization of activated carbons was performed by nitrogen adsorption at 77 K. The energetic parameters were determined by immersion calorimetry in benzene and water. In addition, the total acidity and basicity were estimated using Boehm titrations. A maximum surface area of 1700 m2 g−1 was obtained with a pore volume of 0.64 cm3 g−1. Immersion calorimetry provided results between −17.95 and −95.75 J g−1 in benzene and between −13.63 and −30.24 J g−1 in water. The materials had a maximum CO2 adsorption capacity of 5.75 mmol CO2 g−1. It was found that the adsorption of gas increased with the total basicity and decreased with acidity. Finally, correlations were established between the textural characteristics, determined by gas adsorption and the immersion enthalpy data.

Effect of textural and chemical characteristics of activated carbons on phenol adsorption in aqueous solutions

Abstract The effect of textural and chemical properties such as: surface area, pore volume and chemical groups content of the granular activated carbon and monoliths on phenol adsorption in aqueous solutions was studied. Granular activated carbon and monolith samples were produced by chemical activation. They were characterized by using N2 adsorption at 77 K, CO2 adsorption at 273 K, Boehm Titrations and immersion calorimetry in phenol solutions. Microporous materials with different pore size distribution, surface area between 516 and 1685 m2 g−1 and pore volumes between 0.24 and 0.58 cm3 g−1 were obtained. Phenol adsorption capacity of the activated carbon materials increased with increasing BET surface area and pore volume, and is favored by their surface functional groups that act as electron donors. Phenol adsorption capacities are in ranged between 73.5 and 389.4 mg · g−1.

Calorimetric study of activated carbonsimpregnated with CaCl2

Abstract Activated carbon monoliths with different surface characteristics were prepared by impregnating oil palm stone with diluted aqueous CaCl2 solutions (with concentrations between 2 and 7% w/v) without binders. The solids were characterized by determination of nitrogen adsorption isotherms at 77 K and carbon dioxide adsorption isotherms at 273 K using volumetric adsorption equipment. Surface area and micropore volume values were calculated from the nitrogen isotherms using the BET and DR models, respectively, obtaining solids with low percentages of mesoporosity. Immersion enthalpies of the activated carbon monoliths were determined in benzene, with values between -173 and -104 J g-1, and water, with values between 61 and 30 J g-1, indicating that the monoliths have a hydrophobic character. Graphical Abstract

Textural Characteristics and Energetic Parameters of Activated Carbon Monoliths: Experiments and Monte Carlo Simulations †

Disc-type activated carbon monoliths were prepared through chemical activation of coconut shell and African palm pits with phosphoric acid at different concentrations, without using any binder. The structures thereby produced were studied experimentally by nitrogen adsorption at 77 K, carbon dioxide adsorption at 273 K and immersion calorimetry in benzene. The experimental data allowed the textural and energetic characterization of the microporous solids to be obtained, viz. BET areas between 752 and 1711 m2/g, micropore volumes between 0.32 and 0.61 cm3/g, ultramicropore volumes between 0.11 and 0.24 cm3/g and immersion enthalpy values between 95.85 and 147.7 J/g. Grand Canonical Monte Carlo (GCMC) simulations were used to analyze the experimental results, providing an interpretation of, as well as a more detailed characterization, of the textural properties, such as the determination of the pore-size distribution (PSD) of each material.