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Adsorption: Journal of the International Adsorption Society (v.12, #1)
Fixed-bed adsorption of carbon dioxide/methane mixtures on silicalite pellets by José A. Delgado; María A. Uguina; José L. Sotelo; Beatriz Ruíz; José M. Gómez (pp. 5-18).
The adsorption of carbon dioxide and methane on silicalite pellets packed on a fixed bed has been studied. Equilibrium and kinetic measurements of the adsorption of carbon dioxide and methane have been performed, and a binary adsorption isotherm for carbon dioxide/methane mixtures has been obtained. A model based on the LDF approximation for the mass transfer has been used to describe the breakthrough curves obtained experimentally. A PSA cycle has been proposed for obtaining methane with purity higher than 98% from carbon dioxide/methane mixtures containing 38% and 50% methane, and its performance has been simulated using the proposed model. The simulation results show that silicalite can be a suitable adsorbent for employment in a PSA separation process for carbon dioxide removal from coalseam and landfill gases.
Keywords: Carbon dioxide; methane; silicalite; adsorption; fixed-bed; PSA simulation
Use of x-ray microtomography to visualise dynamic adsorption of organic vapour and water vapour on activated carbon by P. Lodewyckx; S. Blacher; A. Léonard (pp. 19-26).
X-ray microtomography coupled with image analysis was used to quantify the adsorption of vapours on activated carbon beds. This technique was tested using three different challenges: CCl4, water vapour and a mixture of water- and organic vapour. It is shown that the used technique allows determining the adsorption front progress in the case of organic vapour and mixture of water and organic vapour whereas the existence of this front was not so obvious in the case of water vapour. Experimental results obtained for organic vapours were interpreted on the basis of the Wheeler-Jonas equation: a good agreement was found between experimental and theoretical breakthrough times.
Keywords: Activated carbon; Adsorption; Tomography; Modelling
Rice husk ash as an adsorbent for methylene blue—effect of ashing temperature by Sathy Chandrasekhar; P. N. Pramada (pp. 27-43).
Utilization of one waste material to control pollution caused by another is of high significance in the remediation of environmental problems. Rice husk, an abundantly available agricultural waste, can be used as a low cost adsorbent for dyes and heavy metals in effluent streams. The possible utilization of rice husk ash as an adsorbent for methylene blue dye from aqueous solutions has been investigated. Ash samples from husks of two origins were prepared at different temperatures and their physical, chemical spectroscopic and morphological properties were determined. XRD, FTIR and SEM were some of the techniques adopted for the characterization. The samples were also analyzed for bulk density, pH, nitrogen adsorption properties and lime reactivity. Experiments of methylene blue adsorption on the ash samples were conducted using batch technique and a comparative study was made. Results were analyzed using linear, Langmuir and Freundlich isotherms. The values of separation factor indicate that most of the ash samples do adsorb the dye molecules, but in varying quantities. Calcination at 900∘C reduces the adsorption capacity of the ash to a great extent. Regression analysis shows that the experimental data fits both Langmuir and Freundlich isotherms for certain concentration limits. The adsorbate species are most probably transported from the bulk of the solution into the solid phase through intra-particle diffusion process. Kinetics of adsorption was found to follow pseudo second order rate equation with R 2∼ 0.99. The highest adsorption capacity (Q 0) achieved is found to be ∼690 mg/g, which is even higher than the values reported for activated carbon from rice husk. The adsorption capacity of the ash samples are in good agreement with their surface area and pore volume.
Keywords: Rice husk ash; Silica; Adsorption; Calcination; Methylene blue
Ethane adsorption in slit-shaped micropores: influence of molecule orientation on adsorption capacity by G. Calleja; B. Coto; A. Pinar; A. M. Morales-Cas (pp. 45-54).
Adsorption of ethane in a slit shaped micropore system has been studied by Monte Carlo molecular simulation by considering this hydrocarbon as a two interacting sites molecule. Ethane adsorption in pore sizes from 0.41 to 1.66 nm was simulated at 303 K. Microscopic characteristics of the adsorbed phase have been studied for pores of different size, comparing two density profiles: the molecule centre of mass profile and the molecular interaction site profile. Averaged angle distribution of molecule positions with respect to the slit plane across the pore width has been also obtained by simulation. These results were related to ethane molecule packing efficiency, which is also related to the adsorption capacity in terms of the adsorbed phase density. Packing efficiency presents an oscillation shape as the result of the adsorbate disorder inside the pore.Pressure influence on the adsorption has been studied by following pore filling by simulation. When pore condensation takes place and for pressures above condensation, fluid-fluid interactions are determinant in molecule disorder observed between the two adsorbed layers.
Keywords: Activated carbon; Slit pore model; Molecular simulation; Monte Carlo simulation; Ethane
Carbon dioxide-methane mixture adsorption on activated carbon by V. Goetz; O. Pupier; A. Guillot (pp. 55-63).
In this work, we report new experimental data of pure and binary adsorption equilibria of carbon dioxide and methane on the activated carbon RB2 at 273 and 298 K. The pressure range studied were 0–3.5 MPa for pure gases and 0–0.1 MPa for mixtures. The combination of the generalized Dubinin model to describe the pure CO2 and CH4 isotherms with the IAST (Ideal Adsorbed Solution Theory) for the mixtures provide a method for the calculation of the binary adsorption equilibria. This formulation predicts with acceptable accuracy the binary adsorption data and can easily be integrated in general dynamic simulation of PSA (pressure swing adsorption process) adsorption columns. It involves only three parameters, independent of the temperature, and directly determined with only one adsorption isotherm of CO2.
Keywords: Adsorption; Mixture; Activated carbon; Volumetric method; Experimental data; Modelling
Equilibrium and kinetics study of Gd(III) and U(VI) adsorption from aqueous solutions by modified Sorrel’s cement by M. S. Gasser; G. A. Morad; H. F. Aly (pp. 65-76).
Modified Sorrel’s cement was prepared by the addition of ferric chloride. The modified cement (MF5) was analyzed and characterized by different methods. Adsorption of Gd(III) and U(VI) ions in carbonate solution has been studied separately as a function of pH, contact time, adsorbent weight, carbonate concentration, concentration of Gd(III) and U(VI) and temperature. From equilibrium data obtained, the values of Δ H, Δ S and Δ G were found to equal −30.9 kJ ⋅ mol−1, −85.4 J ⋅ mol−1 ⋅,K−1, and −5.4 KJ ⋅ mol−1, respectively, for Gd(III) and 18.9 kJ ⋅ mol−1, 67.8 J ⋅ mol−1 K−1 and −1.3 KJ ⋅ mol−1, respectively, for U(VI). The equilibrium data obtained have been found to fit both Langmuir and Freundlich adsorption isotherms. The batch kinetic of Gd(III) and U(VI) on modified Sorrel’s cement (MF5) with the thermodynamic parameters from carbonate solution were studied to explain the mechanistic aspects of the adsorption process. Several kinetic models were used to test the experimental rate data and to examine the controlling mechanism of the adsorption process. Various parameters such as effective diffusion coefficient and activation energy of activation were evaluated. The adsorption of Gd(III) and U(VI) on the MF5 adsorbent follows first-order reversible kinetics. The forward and backward constants for adsorption, k 1and k 2 have been calculated at different temperatures between 10 and 60∘C. Form kinetic study, the values of Δ H * and Δ S * were calculated for Gd(III) and U(VI) at 25∘C. It is found that Δ H * equals −14.8 kJmol−1 and 7.2 kJmol−1 for Gd(III) and U(VI), respectively, while Δ S * were found equal −95.7 Jmol−1K−1 and −70.5 Jmol−1K−1 for Gd(III) and U(VI), respectively. The study showed that the pore diffusion is the rate limiting for Gd(III) and (VI).
Keywords: Adsorption; equilibrium; Kinetics; Gd(III); U(VI); modified cement
Uptake of Basic Blue 17 from aqueous solutions by using chemically crosslinked polyelectrolyte AAm/AASS hydrogels by Ömer Barış Üzüm; Erdener Karadağ (pp. 77-88).
In this study, the removal of a cationic thiazin dye such as Basic Blue 17 (Toluidin Blue, BB 17) by chemically crosslinked acrylamide (AAm)/acrylic acid sodium salt (AASS) hydrogels was investigated. Super water retainer AAm/AASS hydrogels with various compositions were prepared from ternary mixtures of AAm, AASS and water by free radical polymerization in aqueous solution using multifunctional crosslinkers such as ethylene glycol dimethacrylate (EGDMA), N,N′ methylenebisacrylamide (NMBA), 1,4 butanediol dimethacrylate (BDMA) and trimethylolpropane triacrylate (TMPTA). Adsorption of Basic Blue 17 from aqueous solutions was studied by batch sorption technique at 25∘C. The effect of Basic Blue 17 concentration and mass of adsorbent on the dye adsorption were examined.In the experiments of the sorption, C type and L type sorption in the Giles classification system was found. Some binding parameters such as initial binding constant (K i ), equilibrium constant (K), monolayer coverage (n), site-size (u), and maximum fractional occupancy (Ô) for AAm/AASS hydrogel-dye binding system were calculated by using Klotz linearization method. Finally, the amount of sorbed Basic Blue 17 per gram of dry hydrogel (q) was calculated to be 1.96–21.35 μ mol dye per gram for AAm/AASS hydrogels. Adsorption of Basic Blue 17 was changed range 39.17–96.63%. AAm/AASS hydrogels crosslinked by TMPTA, EGDMA, BDMA or NMBA can be used a sorbent in biotechnology, environment, sorption, separation, purification, immobilization and enrichment of some species.
Adsorption of Promethazine hydrochloride with KSF Montmorillonite by Yoldaş Seki; Kadir Yurdakoç (pp. 89-100).
Adsorption of Promethazine hydrochloride (PHCl) onto KSF Montmorillonite from aqueous solution has been investigated. Experiments were conducted at various pH values, ionic backgrounds and solution temperatures. The pseudo-second-order equation successfully predicted the adsorption among the tried kinetics models (pseudo-first-order, pseudo-second-order and intraparticle diffusion). Langmuir, Freundlich and DR adsorption models were used to describe equilibrium isotherms and the isotherm constants were obtained. The increase in solution temperature caused a decrease in the adsorption capacity values found from Freundlich and DR isotherm. The adsorption type can be explained by combined ion exchange and physisorption. Thermodynamic parameters of adsorption of Promethazine hydrochloride (PHCl) onto KSF were also evaluated. The surface morphologies of KSF and PHCl loaded KSF were examined using a scanning electron microscope (SEM). FTIR measurements of samples were also conducted.
Keywords: KSF; drug; kinetic; thermodynamic parameters