Magnitude of Adsorption

Now if A is the adsorbent surface area and t the thickness of the adsorbed layer, then the volume of the adsorbed layer, or adsorption space is [4]  

The Physical Chemistry of Materials Energy and Environmental Applications 

We now precisely define some surface parameters. If the mass of a degassed adsorbent is defined as ms and measured in grams, subsequently, the specific surface area is 

The specific surface excess amount is what is typically measured in practical adsorption studies (see Section 6.4). This parameter is almost equal to the amount adsorbed, a, and is dependent on the equilibrium adsorption pressure, P, at constant adsorbent temperature, T. Accordingly, gas adsorption data is, in practice, expressed by the adsorption isotherm  

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Table I. Magnitudes of Adsorption Potential Parameters for Adsorption of 02 and N2 on Anatase at T = 78.2° K."...

The variation of adsorption with pressure at a given constant temperature is generally expressed graphically as shown in the figure given above. Each curve is known as adsorption isotherm for a particular temperature. The relation ship between the magnitude of adsorption and pressure can be expressed mathematically by a empirically equation commonly known as Freundlich adsorption isotherm, viz. 

Combining these results of Eq. 6.6 it is evident that according to this theory, the magnitude of adsorption at a given temperature... 

Some very simple diffusion models have been given by Dukhin et al. [2], however these models are only useful for estimating the order of magnitude of adsorption or desorption processes. Based on comprehensive quantitative models approximations have been derived the application of which is often very useful [15, 16]. 

Since the presence of salts urge the polymer molecules to coil up, the amount of polymer in the adsorbed layer increases with increasing salt concentration. In addition, a higher degree of polymer hydrolyzation leads to a greater polymer adsorption on the pore walls. Thus, these polymer molecules in caustic media would exhibit a high magnitude of adsorption. 

When the adsorption of same fatty acids from aqueous solutions was studied on a charcoal prepared under strongly oxidizing conditions (Figure 3.29), Traube s rule shows a reversal, which means that the magnitude of adsorption decreases as we ascend the homologous series. This has been attributed to the polar nature of the charcoal surface, due to the presence of polar carbon-oxygen surface groups, which... 

Sohail and Qadeer studied the adsorption of Pb(II) ions from aqueous solutions on commercial activated carbons and determined optimum conditions for maximum adsorption in terms of the time of contact, solution concentration, and temperature. The adsorption was found to obey first-order kinetics. The magnitude of adsorption energy calculated from D-R equation was found to be 7.61 KJ/mol, which showed that the adsorption involved weak bonding between the Pb + ions and the activated carbon surface, Yang et al. used two activated carbons obtained from coal for... 

The magnitude of adsorption heat corresponds to the strength of adsorption bond, and so there should also be some relationship between adsorption and catalytic activity. The catal3dic activity is reversely proportional to adsorption strength when the surface coverage of reaction molecule reaches certain level, as indicated by Sabatier s theory of intermediate complex and experience. On the other hand, if adsorption is too weak, it is difficult to activate adsorbed molecules. The best activity can be obtained only in the case with suitable adsorption strength. This relationship is usually called as a volcano type curve, as shown in Fig. 2.4. 

By successive calculations [12], it is possible to determine the magnitude of adsorption, a, for an equilibrium concentration of adsorbate, c, in the mobile phase ... 

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