Adsorbents saturation

Figure 3.1 The five isotherm classifications according to BDDT. W, weight adsorbed F, adsorbate equilibrium pressure Pq, adsorbate saturated equilibrium vapor pressure P/Pq, relative pressure. Condensation occurs at P/Pq >1.

Ebk Monochromatic-emissive power of blackbody radiation Po adsorbate Saturated vapor pressure... 

As noted above, the results exhibit trends for changes between clean and chemisorbed surfaces. Once chemisorption occurs, the adsorbates saturate the dangling bonds by bonding with the surface atoms. The bonding causes a charge transfer between the adsorbates and the surface atoms, and an additional... 

An adsorbed saturated molecule with a single bond may dissociate into two radicals, one saturated with the surface valence, and... 

Sorption equilibria and kinetics are influenced by the nature of the adsorbent and the adsorbate, by the mechanism of adsorption, and by environmental parameters such as temperature, relative humidity, concentration of the adsorbate, and air velocity and turbulence past the adsorbent surface. Air velocity and turbulence only affect sorption kinetics the other parameters also affect equilibria. In general, low adsorbate saturation vapor pressure, low temperature, and high adsorbate concentration in the air increase adsorption. Relative humidity does not always affect adsorption. Colombo et al. (1993) found a 35 % decrease in adsorbed mass when relative humidity was changed from <10 % to 35 %, but only an 8 % decrease when the humidity was increased from 35 % to 70 %. Building materials, which are exposed to indoor air in the normal humidity range of 35-70 %, will typically already be covered by at least one monolayer of adsorbed water, and the formation of multilayers will only have a limited influence on sorption properties for other airborne substances. Kirchner et al. (1997) found that an increase in air velocity increased the rate of desorption of a VOC mixture from painted gypsum, but not from carpet. The air velocity of air above the tuft may be insignificant for the desorption processes of carpet fibers deeper in the tuft. 

The NMR peak area from an adsorbate saturating the solid can be measured as a function of temperature. As the frozen adsorbate is solid, nuclei in this phase will have very short spin-spin relaxation times. Hence, signal from the frozen adsorbate can easily be eliminated by using a spin-echo pulse sequence, or by increasing the specified dead-time after the excitation pulse. This means that the relative amount of liquid present in the pores can be measured by variable-temperature NMR methods. An intensity correction to allow for the change in the Boltzmann equilibrium population of energy levels with temperature is also required ... 

GaoP, LinCH, Shannon C, SalaitaGN, White JH, Chaffins SA, Hubbard AT (1991) Studies of adsorbed saturated alcohols at Pt(l 11) electrodes by vibrational spectroscopy (EIiLS), Auger-spectroscopy, and electrochemistry. Langmuir 7 1515-1524... 

It is seen in Eq. (29) that the DR equation requires two types of parameters (1) properties of the adsorbent-micropore volume Vo and characteristic energy Eq-, (2) properties of the adsorbate — saturation pressure Pg, affinity coefficient P, and liquid molar volume. Principally, the first group of parameters are temperature-independent and can be obtained from the adsorption of a reference adsorbate on the same adsorbent, while the second group of parameters are temperature-dependent but can be simply estimated from the thermodynamic properties of each species. Therefore, a limited set of data is required to describe binary adsorption over a wide range of pressure and temperature. Thus the advantages of using the DR equation deserve to be exploited. 

Po.i V Adsorbed volume at the adsorbent Vg Adsorbent saturation volume at = 1... 

The above considerations about the real adsorption system can be extended to the adsorption at the solid/liquid interface [16-22]. With regard to nonporous solids or solids with large pores the concept of specific surface area (the surface area divided by the mass of the solid) has a real physical meaning. Therefore, in such solid/fluid systems, the interfacial layer denotes the surface phase formed on the surface of a solid adsorbent. The macroscopic concept of the specific surface area loses physical meaning for microporous solids i.e., for the solids with pores of molecular dimensions [23]. The microporous adsorbents saturated by adsorbate molecules are rather considered as a uniphase system [24-25]. Cohsequently, the aforementioned concept of interfacial layer should be used most adequately with respect to uptake of fluids by microporous solids. 

Evaluation of surface acidity can also be carried out in the gas phase by contacting adsorbents saturated with a carrier gas, such as He, with gaseous ammonia or another base. The adsorption and the determination of the heats of adsorption can be carried out at high pressures which may produce results altogether different to the measurements of adsorption at very low surface coverages and the associated low partial pressures of gaseous bases at which they may totally saturate the adsorbent surface. 

The dimensionless coefficient f, which additionally characterises a degree of adsorbent saturation in the zone of mass transfer is given by the following... 

When the supplier accepts deUvery of the returned canister containing adsorbent saturated with solvent vapor, they must accept legal responsibility for compliant disposal ofthe adsorbed solvent. Normallythegeneratorofhazardous waste (in the US) is responsible formanagement ofthe waste from "cradle to grave." However as part of written business relationships, this responsibility may be transferred. 

Fig. 39 shows the dependence of hydrodynamic thickness 3 of an adsorbed saturated PEO layer on the tangential shear stress t = r APjlL acting on the peripheric part of the layer, where r is the capillary radius and L is the length of the capillary. The obtained dependence is reversible. This points to elastic or viscoelastic deformation of adsorbed layers. Thin quartz capillaries represent a simple model system that may be effectively used for investigation of both electrosurface phenomena and mechanical properties of adsorbed layers of surface-active polymers. 

By addition to the adsorbent, saturated by adsorbed pol5uner, of an additional portion of the same adsorbent, there was observed an essential increase in the fraction of bound segments, p, as followed from the NMR measurements. This fact indicates formation of bridges between various particles of adsorbent, connected by macromolecules adsorbed on both particles simultaneously. This... 

Equilibrium pressure of adsorbate Saturation pressure of adsorbate Reduced pressure Saturation pressure Total power for a stack... 

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