Adsorption isotherms data processing

During metal deposition processes the addition of adsorbable species has been found to cause an increase in the deposition overpotential [71 Lou]. Evaluation of the data results in the calculation of an adsorption isotherm. (Data obtained with this method are labelled CT.)... 

For the detailed study of reaction-transport interactions in the porous catalytic layer, the spatially 3D model computer-reconstructed washcoat section can be employed (Koci et al., 2006, 2007a). The structure of porous catalyst support is controlled in the course of washcoat preparation on two levels (i) the level of macropores, influenced by mixing of wet supporting material particles with different sizes followed by specific thermal treatment and (ii) the level of meso-/ micropores, determined by the internal nanostructure of the used materials (e.g. alumina, zeolites) and sizes of noble metal crystallites. Information about the porous structure (pore size distribution, typical sizes of particles, etc.) on the micro- and nanoscale levels can be obtained from scanning electron microscopy (SEM), transmission electron microscopy ( ), or other high-resolution imaging techniques in combination with mercury porosimetry and BET adsorption isotherm data. This information can be used in computer reconstruction of porous catalytic medium. In the reconstructed catalyst, transport (diffusion, permeation, heat conduction) and combined reaction-transport processes can be simulated on detailed level (Kosek et al., 2005). 

Eqns (16), (20) and (22) were integrated numerically to obtain the separation performance of the one- and two-column processes The GEAR package (13) was used for the integration after determining that it was faster than, say, Runge-Kutta methods For all calculations N 50 and e - 0.40 Dimensionless parameters varied were 8, ph pL Yf and, for the two-column process, H. Combinations of the parameters of 6 and Pr/Pl were chosen to correspond to the me thane-helium system on BPL carbon Adsorption isotherm data for methane at 25°C (14) were represented by... 

Further information on the adsorption process may be obtained from adsorption isotherm data. The construction of these isotherms for liquid phase processes differs from the well-known gas phase adsorption isotherms. For the liquid phase adsorption, the surface loading is plotted as a function of the equilibrium concentration of adsorbate (Cf). 

Considering the nature of the forces involved in the physical adsorption process (see Section 4.2.1), it is evident that the adsorption isotherm of a given adsorptive on a particular solid at a given temperature depends on the nature of both the gas and the solid, and therefore, each adsorbate-adsorbent system has a unique isotherm. In spite of this, a number of attempts have been made to express the adsorption isotherm data in a normalized form. It was seen that, for a large number of nonporous solids (type II isotherms), the plot of n/nm versus P/P° can be represented by a single curve, called the standard isotherm. Among these related attempts, the t- and as-methods are the most widely used. 

B.K. Kaul, Correlation and prediction of adsorption isotherm data for pure and mixed gases, Ind. Eng. Chem. Process. Des. Dev. 2i 711 (1984). 

Aside from adsorption isotherm data one can use calorimetric techniques to obtain information on the thermodynamic properties of materials adsorbed on surfaces. The experimental techniques are now more involved but they do supply direct information on the heats liberated during the adsorption process. Here the use of partial molal quantities is imperative since increments of the heats of adsorption diminish with successive amounts of gas transferred to the adsorbed phase. Here we follow the systematic treatment furnished by Clark. ... 

The introduction of a range of user-friendly equipment and software has accompanied the present widespread use of low-temperature nitrogen adsorption. Advances have been made in the development of both routine experimental procedures and on-line processing of the adsorption isotherm data. However, there is now a risk that an unskilled operator may gain the impression that with the aid of a manufacturer s user-friendly software it is relatively easy to evaluate the specific surface area and the pore size distribution of the material under examination. Furthermore, the ready access to sophisticated computational procedures may tend to obscure the limitations of the theoretical models on which they are based. The aims of this paper are to draw attention to these problems and to indicate how further progress can be made in the analysis of nitrogen isotherms on porous carbons. 

Despite the limitations mentioned above, the chromatographic method is easy to handle and generates adsorption isotherm data quickly for a large number of combinations of polymers and gases or vapors. These data are important when membrane gas separation and pervaporation data are interpreted, and polymer materials are chosen for the preparation of membranes used for the above separation processes. 

Surface areas are deterrnined routinely and exactiy from measurements of the amount of physically adsorbed, physisorbed, nitrogen. Physical adsorption is a process akin to condensation the adsorbed molecules interact weakly with the surface and multilayers form. The standard interpretation of nitrogen adsorption data is based on the BET model (45), which accounts for multilayer adsorption. From a measured adsorption isotherm and the known area of an adsorbed N2 molecule, taken to be 0.162 nm, the surface area of the soHd is calculated (see Adsorption). 

Cost estimation and screening external MSAs To determine which external MSA should be used to remove this load, it is necessary to determine the supply and target compositions as well as unit cost data for each MSA. Towards this end, one ought to consider the various processes undergone by each MSA. For instance, activated carbon, S3, has an equilibrium relation (adsorption isotherm) for adsorbing phenol that is linear up to a lean-phase mass fraction of 0.11, after which activated carbon is quickly saturated and the adsorption isotherm levels off. Hence, JC3 is taken as 0.11. It is also necessary to check the thermodynamic feasibility of this composition. Equation (3.5a) can be used to calculate the corresponding... 

Adsorption isotherms obtained from the model have been shown to agree very closely with the predictions of recently published statistical theories (9,13). While there can be no doubt that the more sophisticated, statistical models provide more information on the nature of the adsorption process and the structure of the adsorbed film, because of its simple form, the macroscopic model can offer a powerful tool for the analysis, interpretation and utilization of adsorption data. 

The adherence of experimental sorption data to an adsorption isotherm equation provides no evidence as to the actual mechanism of a sorption process. 

Multicomponent pollutants in an aqueous environment and/or leachate of SWMs, which are COMs, usually consist of more than one pollutant in the exposed environment [1, 66-70]. Multicomponent adsorption involves competition among pollutants to occupy the limited adsorbent surface available and the interactions between different adsorbates. A number of models have been developed to predict multicomponent adsorption equilibria using data from SCS adsorption isotherms. For simple systems considerable success has been achieved but there is still no established method with universal proven applicability, and this problem remains as one of the more challenging obstacles to the development of improved methods of process design [34,71 - 76]. 

Abstract Removal of catechol and resorcinol from aqueous solutions by adsorption onto high area activated carbon cloth (ACC) was investigated. Kinetics of adsorption was followed by in-situ uv-spectroscopy and the data were treated according to pseudo-first-order, pseudo-second-order and intraparticle drfiusion models. It was fotmd that the adsorption process of these compotmds onto ACC follows pseudo-second-order model. Furthermore, intraparticle drfiusion is efiective in rate of adsorption processes of these compoimds. Adsorption isotherms were derived at 25°C on the basis of batch analysis. Isotherm data were treated according to Langmuir and Freundhch models. The fits of experimental data to these equations were examined. 

The sorption process generally is studied by plotting the equilibrium concentration of a compound on the adsorbent, as a function of equilibrium concentration in the gas or solution at a given temperature. Adsorption isotherms are graphs obtained by plotting measured adsorption data against the concentration value of the adsorbate. Several mechanisms may be involved in the retention of contaminants on... 

The deviations from the Szyszkowski-Langmuir adsorption theory have led to the proposal of a munber of models for the equihbrium adsorption of surfactants at the gas-Uquid interface. The aim of this paper is to critically analyze the theories and assess their applicabihty to the adsorption of both ionic and nonionic surfactants at the gas-hquid interface. The thermodynamic approach of Butler [14] and the Lucassen-Reynders dividing surface [15] will be used to describe the adsorption layer state and adsorption isotherm as a function of partial molecular area for adsorbed nonionic surfactants. The traditional approach with the Gibbs dividing surface and Gibbs adsorption isotherm, and the Gouy-Chapman electrical double layer electrostatics will be used to describe the adsorption of ionic surfactants and ionic-nonionic surfactant mixtures. The fimdamental modeling of the adsorption processes and the molecular interactions in the adsorption layers will be developed to predict the parameters of the proposed models and improve the adsorption models for ionic surfactants. Finally, experimental data for surface tension will be used to validate the proposed adsorption models. 

Figure 34 shows the results for alcohol (methanol, ethanol, 1-propanol and 1-butanol), ketone (acetone and diacetyl), terpene (pinene and linalool), aldehyde (n-nonyl aldehyde) and ester (acetic acid n-amyl ester and n-butyric acid ethyl ester) of various concentrations. Because of the linear characteristics of the CTL-based sensor, the plots are located in a similar region for a certain type of gas of various concentrations where the Henry-type adsorption isotherm holds. Thus, we can identify these gases with various concentrations by simple data-processing. 

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