Adsorption isotherm data

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.)... 

Here, N is the amount of adsorption and X is the relative pressure (P/Po). Ds can be calculated through the slope of a log-log plot of Eq. (3) by a single nitrogen adsorption isotherm data. 

According to this relation, the distribution function K can be estimated from the chromatographic data of a solute using pure solvents as the mobile phase. Equation 4.25 shows that the difference j for each component of the mobile phase can be calculated without the adsorption isotherm data. 

A graph of q w) against m, or an equivalent concentration variable, at fixed temperature and pressure is an adsorption isotherm. Data of this kind typically have been fitted numerically to special cases of the equation (3) ... 

The number of polymer molecules adsorbed per unit area was calculated from adsorption isotherm data and the surface area per unit mass of the sample. 

Kim H, Guiochon G. Adsorption on molecularly imprinted polymers of structural analogues of atemplate. Single-component adsorption isotherm data. Anal Chem 2005h 77 6415-6425. 

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). 

As has been depicted in Fig. 1, various conformations are possible for adsorbed polymers, depending on polymer-polymer, polymer-solvent, and polymer-interface interactions and the flexibility of polymers. To determine experimentally the conformation of adsorbed polymers only adsorption isotherm data are insufficient. The average thickness of the adsorbed polymer layer, the segment density distribution in this layer, the fraction of adsorbed segments, and the fraction of surface sites occupied by adsorbed segments must be measured. Recently, several unique techniques have become available to measure these quantities. 

Adsorption of 4-aminobenzoic acid (ABZA) and 3-chloro-4-hydroxyben-zoic acid (CHBZA) was studied by Cunningham and Al-Sayyed (1990). Adsorption isotherm data were collected and analyzed to determine what role adsorption plays in influencing photocatalytic efficiencies. The Lang-muir-Hinshelwood kinetic model was applied and limitations of this model are discussed. 

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). 

In this section, several theories and equations for the analysis of the adsorption isotherm data will be presented. The starting assumptions used in each equation will be discussed for a proper understanding of its limitations and correct use in the characterization of porous carbons. 

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. 

Below the adsorption isotherm data, the detailed pore size distribution data are listed in seven columns. These include the pore radii corresponding to the 64 data points, the volume of liquid nitrogen desorbed at each step, the mean pore radii corresponding to each of the desorbed decrements, the pore volume per unit change in radius (AV/Ar), the cumulative pore volumes at each pore radius, the calculated surface area in each of the pore radius steps, and the cumulative pore areas in pores larger than each of the listed radii. The print-out sheet is completed with the two sections discussed in connection with Figure 2. 

In conclusion, definite information on the density of adsorbed interlayer water cannot be derived from the bulk density measurements. However, such measurements supplement adsorption isotherm data, and both will be helpful in the interpretation of x-ray structure analysis of the configuration of water molecules and exchange cations in the interlayer space. 

The following three main routes are available to assess the wettability. The first method is dependent on the measurement of contact angles, while the second and third make use of energy of immersion and adsorption isotherm data. 

In the light of these results, it is of interest to obtain accurate adsorption isotherm data at very low p/p°. As explained in Chapter 3, such high resolution adsorption (HRADS) measurements are not easy to make, but a preliminary investigation (Kenny et al., 1993) indicated that the primary filling of the micropores in Carbosieve by nitrogen at 77 K begins at p/p° < 10-s and is complete atp/pa 10 2. These findings have been broadly conArmed by the recent work of Conner (1997) and Kaneko (1997). 

Table 1 shows the adsorption isotherm data and acidity measurements for the samples under examination. Figures 1 and 2 show the nitrogen adsorption isotherms for the copper-containing and manganese-containing samples respectively. 

From the adsorption isotherm data, it could be deduced that the incorporation of CO2 to the gas stream does not change the Phe adsorption mechanism on the carbonaceous material surface. This fact was not observed when steam is involved in the Phe adsorption. 

It has to be mentioned that the micropore surface area values, calculated by Stoeckli-Ballerini equation [9], present a maximum value with the burn-off degree of the samples, either from the N2 or CO2 adsorption isotherms data. This is due to the increase in the pore size (L values), and the assumptions made in the equations. Thus, as the pore size -L- increases, the micropore surface area for a determined micropore volume -Wo- is smaller. 

The main purpose of the present work is twofold (i) to report an extensive set of singlecomponent adsorption isotherm data of the more common natural gas components on activated carbon, and (ii) to present a means of extrapolating the measured data to higher alkanes in order to be able to span the whole composition of a typical natural gas. There is experimental evidence that for the n-alkanes series this can be done using the Adsorption Potential theory, as demonstrated recently by Holland et al. on Westvaco BAX-1100 carbon, and assumed previously by us. - ... 

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. ... 

In order to characterize the micropore structure by obtaining the MSD from adsorption isotherm data, it is necessary to obtain a collection of simulated isotherms for different size d, (/ = 1,. . ., ), in the form of adsorbed volume of gas at STP as a function of p i] d, p). Then, assuming the hypothesis of independent pores as valid, as commonly done, the global theoretical isotherm for a microporous material having a size distribution/ (d,) can be written as ... 

Fig. 2. Adsorption isotherm data and model fitting of ethane and propane in Norit activated carbon ------ MPSD model -------------Energy distribution model...

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