Adsorption, apparent physical

Accordingly, extractant adsorption takes place through the Van der Waals interaction between alkyl radicals with a matrix surface (physical adsorption). Apparently, such an interaction will be stronger at the increase of contact of butyl radicals with the surface. An increase of TBP interaction with matrix corresponds to a decrease of h and increase of r. Since conformers F and B have the lowest h (0.47 and 0.48 nm) and the highest r (0.82 and 0.78 nm), it may expected that their highest bonding strength is with the matrix surface. Conformer A has the lowest radius r = 0.65 nm and, hence, is adsorbed worst by matrix. 

Not all of the sites on a surface are identical. Further, broadly, chemisorption involves strong interactions between adsorbant and surface.This type of adsorption may involve interactions whose strengths approximate those of true chemical bonds. At the opposite extreme, physical adsorption, apparently involves weaker bonding to the surface. 

The expression in brackets is a more usable dependency [Eq. (30)] and describes the physical sense of the apparent dipole moment p. The model up to now has been used only for adsorption from solution. 

The physical meaning of the g (ion) potential depends on the accepted model of an ionic double layer. The proposed models correspond to the Gouy-Chapman diffuse layer, with or without allowance for the Stem modification and/or the penetration of small counter-ions above the plane of the ionic heads of the adsorbed large ions. " The experimental data obtained for the adsorption of dodecyl trimethylammonium bromide and sodium dodecyl sulfate strongly support the Haydon and Taylor mode According to this model, there is a considerable space between the ionic heads and the surface boundary between, for instance, water and heptane. The presence in this space of small inorganic ions forms an additional diffuse layer that partly compensates for the diffuse layer potential between the ionic heads and the bulk solution. Thus, the Eq. (31) may be considered as a linear combination of two linear functions, one of which [A% - g (dip)] crosses the zero point of the coordinates (A% and 1/A are equal to zero), and the other has an intercept on the potential axis. This, of course, implies that the orientation of the apparent dipole moments of the long-chain ions is independent of A. 

A variety of procedures were utilized to analyze this reaction mixture and to characterize a,10-diaminopolystyrene. Thin layer chromatographic analysis using toluene as eluent exhibited three spots with Rf values of 0.85, 0.09, and 0.05 which corresponded to polystyrene, poly(styryl)amine and a,w-diaminopolystyrene (see Figure 1). Pure samples of each of these products were obtained by silica gel column Chromatography of the crude reaction mixture initially using toluene as eluent [for polystyrene and poly(styryl)amine] followed by a methanol/toluene mixture (5/100 v/v) for the diamine. Size-exclusion chromatography could not be used to characterize the diamine since no peak was observed for this material, apparently because of the complication of physical adsorption to the column packing material. Therefore, the dibenzoyl derivative (eq. 5) was prepared and used for most of the analytical characterizations. 

Hollabaugh and Chessick (301) concluded from adsorption studies with water, m-propanol, and w-butyl chloride that the surface of rutile is covered with hydroxyl groups. After evacuation at 450°, a definite chemisorption of water vapor was observed as well as of n-propanol. The adsorption of -butyl chloride was very little influenced by the outgassing temperature of the rutile sample (90 and 450°). A type I adsorption isotherm was observed after outgassing at 450°. Apparently surface esters had formed, forming a hydrocarbonlike surface. No further vapor was physically adsorbed up to high relative pressures. 

In order to have localized adsorption with only physical interaction it is clear that either the interaction must be strong, or the kinetic energy of the adsorbed molecules must be small. As an example of the latter condition we have the work of Keesom and Schweers (24, 25) for low temperature adsorption of hydrogen and neon on glass. They assumed that the actual area of the glass was equal to the apparent area, and the results in Table IX were worked out for = 3 on that basis. The... 

Polar molecules like II2O show apparent polymerization to an extent quite impossible in the gas phase at low pressures. The dipole field interaction, which is of the order of 1 ev., results in an artificial multilayer physical adsorption at pressures and temperatures where ordinarily only a minute fraction of the first layer would exist. Since multilayer adsorption is quite liquid-like, the high degree of polymerization can be explained. It is interesting to note that at low fields individual peaks show some substructure, which could be due to alignment differences at the time of ionization or could correspond to ionization from different layers within the adsorbate. It is hoped to study physical adsorption near the condensation point at low pressure with nonpolar rare gas atoms to see if layer structure can be elucidated in this way. 

George R. Hill In the low temperature physical solution process the surface area would probably be that determined by BET adsorption measurements. In the high temperature process, apparently the coal structure is opened up, and the surface would be the total surface of all the molecular units. This occurs, as the dissolution proceeds, by a combination of chemical bond breaking and solvent action with hydrogen transfer to the free radicals produced. 

New applications of zeolite adsorption developed recently for separation and purification processes are reviewed. Major commercial processes are discussed in areas of hydrocarbon separation, drying gases and liquids, separation and purification of industrial streams, pollution control, and nonregenerative applications. Special emphasis is placed on important commercial processes and potentially important applications. Important properties of zeolite adsorbents for these applications are adsorption capacity and selectivity, adsorption and desorption rate, physical strength and attrition resistance, low catalytic activity, thermal-hydrothermal and chemical stabilityy and particle size and shape. Apparent bulk density is important because it is related to adsorptive capacity per unit volume and to the rate of adsorption-desorption. However, more important factors controlling the raJtes are crystal size and macropore size distribution. 

We should note that this article by Ya.B. apparently remained little noticed in its time. In any case, we are unaware of any reference to it in the works of other authors. This is explained by the fact that its ideas were far ahead of their time. Only in recent years, due to the wide application of physical methods in studies of adsorption and catalysis, have the changes in the surface (and volume) structure of a solid body during adsorption and catalysis been proved. Critical phenomena have been discovered, phenomena of hysteresis and auto-oscillation related to the slowness of restructuring processes in a solid body compared to processes on its surface. Relaxation times of processes in adsorbents and catalysts and comparison with chemical process times on a surface were considered in papers by O. V. Krylov in 1981 and 1982 [1] (see references at end of Introduction). 

Similar color changes were reported later by Weitz and his collaborators (179), apparently without knowing the older work of the author (180). They describe the bright-red coloration resulting from the physical adsorption of phenolphthalein. 

Physical adsorption of gases and vapors is a powerful tool for characterizing the porosity of carbon materials. Each system (adsorbate-adsorbent temperature) gives one unique isotherm, which reflects the porous texture of the adsorbent. Many different theories have been developed for obtaining information about the solid under study (pore volume, surface area, adsorbent-adsorbate interaction energy, PSD, etc.) from the adsorption isotherms. When these theories and methods are applied, it is necessary to know their fundamentals, assumptions, and applicability range in order to obtain the correct information. For example, the BET method was developed for type II isotherms therefore, if the BET equation is applied to other types of isotherms, it will not report the surface area but the apparent surface area. 

The bulk properties of macroscopic crystals cannot be affected drastically by the difference which exists between the structure of the interior and that of a surface film which is approximately 10,000 atoms deep. However, even for macroscopic crystals, rate phenomena such as modification changes which are initiated within the surface are likely to be influenced by the environment, which would include molecules which are conventionally described as physically adsorbed. Apparently it is not generally understood that even the presence of a noble gas can affect the chemical reactivity of solids. Brunauer (3) explained that in principle physical adsorption of molecules should affect the solid in the same manner as chemisorption. As action and reaction are equal, chemisorption may have a stronger effect on both the solid and the adsorbed molecule. 

The important advances in adsorption technology made possible by the BET theory (S, 4) clearly justify Model 1 in many applications. But one of the Models 2, 3, or 4 is apparently required for first-layer adsorption in a Type II isotherm. That an important condensation potential at the solid-gas interface is the Lennard-Jones 3-9 potential now seems well established (3, 7, 9, 10, 15). Equally clear is the fact that this potential is not solely responsible for physical adsorption the type of surface polarization predicted by the theory of structural adsorption (10) has been demonstrated by observed changes due to adsorption in linear... 

Because of their structural and conformational complexity, polypeptides, proteins, and their feedstock contaminants thus represent an especially challenging case for the development of reliable adsorption models. Iterative simulation approaches, involving the application of several different isothermal representations8,367 369 enable an efficient strategy to be developed in terms of computational time and cost. Utilizing these iterative strategies, more reliable values of the relevant adsorption parameters, such as q, Kd, or the mass transfer coefficients (the latter often lumped into an apparent axial dispersion coefficient), can be derived, enabling the model simulations to more closely approximate the physical reality of the actual adsorption process. 

A zero order with respect to phenol was found, which can be related to the strong physical adsorption of phenol into the zeolite micropores (confinement effect). This explains the pronounced increase in phenol conversion with the methanol/phenol ratio. This strong retention of phenols and phenolic products within the zeolite micropores is responsible for a large part of the high apparent ratio of secondary reactions and especially of coking , i.e. of formation of heavy products which remain trapped in the zeolite micropores. This fast coking of zeolites is responsible for their rapid deactivation by pore blockage. 

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