Adsorption profile

This is the capillary condensation phenomenon, which partiy accounts for the hysteresis observed in adsorption profiles of porous materials. 

The adsorption experiments were carried out by quantifying each of proteins adsorbed on the material from mono-component protein solutions, from four-component protein solutions, and from plasma and diluted plasma. Adsorption profiles of protein were largely different, depending on the aforementioned experimental conditions. For instance, the behavior of any particular protein from diluted plasma varied in response to the extent of plasma dilution. Cooper s results are illustrated in Fig. 3, on fibrinogen adsorption onto five polymer surfaces. It is seen that the adsorption profiles are different one another, being influenced by the different nature of the polymer surfaces. The surface concentrations of adsorbed protein are mostly time-dependent, and maxima in the adsorption profiles were observed. This is interpreted in terms of replacement of adsorbed fibrinogen molecules by other proteins later in time (Vroman effect). Corresponding profiles were also presented for FN and VN. 

Fig. 10. Isometric projection of the adsorption profiles of Br (0.05mM CaBr2) at Pt(lll). Reprinted from ref. 27.

Fig. 16. Adsorption profiles of Cl, Ca, and Q from 0.05 mM CaCl2 (pH = 6.2), 0.1 mM acetate buffer) at Pt(lll) as a function of electrode potential (Ag/AgCl/1 M KC1 reference). Reprinted from ref. 34.

The experimental desorption concentration profiles were obtained in the same way as the experimental adsorption profiles. However, using the local equilibrium model to describe the process, only qualitatively results can be obtained. Mass transfer resistance has stronger effect on desorption in comparison to adsorption so its importance cannot be neglected in the modeling. 

The presence of other materials in the impregnating solution can have a marked effect on the location of the metal within the support particle. These additives have been conveniently divided into three classes. Class 1 additives consist of simple inorganic electrolytes which influence the electrostatic interactions at the solution-support interface. Simple salts such as sodium nitrate, sodium chloride, or calcium chloride do not adsorb strongly enough on alumina to compete with platinum salts for adsorption. Fig. 13.9a 0 shows the concentration profile of platinum on an alumina particle when the impregnation of chloroplatinic acid was done in the absence of any additives. This a somewhat diffused egg shell profile. Fig. 13.9b shows the adsorption profile for the catalyst prepared by impregnation in the presence of an amount of sodium nitrate equimolar to the chloroplatinic acid. Here the amount of platinum adsorbed decreases while the adsorption profile approaches a uniform distribution. It is... 

Class 3 additives are materials such as phosphoric acid and citric acid that can compete with the metal for adsorption sites. While Class 1 and Class 2 additives can control the depth and amount of metal adsorbed leading either to uniform or egg shell catalysts. Class 3 species interfere with platinum adsorption and can give entirely different adsorption profiles. This approach is used, specifically, for the preparation of egg white and egg yolk type catalysts. Fig. 13.11 shows that the platinum distribution is displaced from the surface of the... 

The adsorption process can more likely be attributed to electrostatic interaction. In fact, the increase in temperature raises the surface charge density on the thermally sensitive particle, as evidenced by electrophoretic mobility vs. temperature. In addition, the amount of water is at least close to 30% above the volume phase transition temperature. This adsorption profile (reduced adsorbed amount vs. temperature, as reported in Figure 12.22) is generally observed when the adsorption temperature is well controlled in the case of attractive electrostatic interactions and only the plateau is drastically affected by the pH, salinity, and surface charge density. 

The elution order of the reverse phase HPLC colunm was in decreasing order of anthocyanins polarity. This is similar to the adsorption profile of the cell walls -coumaiyl derivatives followed by caffeyl and then acetyl derivatives ... 

To generate the adsorption isotherm, the leached pulp was contacted with predetermined amounts of carbon, A-500, and AurixlOO in separate experiments. The solution to adsorbents ratio ranged from 30 to 2000 on a dry mass basis of adsorbent. Each test was run for 24 hours, after which time the slurries were filtered and the solutions and adsorbents were analyzed for gold. The adsorption profiles are depicted in Figure 3. ... 

The interaction of oxygen with perovskites has been studied mainly because of the importance of these materials as oxidation-reduction catalysts. Data of oxygen adsorption on LaM03 (M = Cr, Mn, Fe, Co, Ni) oxides were reported by Kremenid et al. (136). The adsorption profile at 25°C showed two maxima for Mn and Co (Fig. 12) that coincide with the maxima observed by Iwamoto et al. (137) for the respective simple oxides... 

Fig. 12. Total (open symbols) and reversible (filled symbols) adsorption profiles of 02 on LaM03 oxides on a clean surface (circles) or on a surface with preadsorbed isobutene (triangles) (P = 2 x 104 Pa T = 25°C). (Reprinted by permission from Ref. 136.)...

An interesting feature of equation (5.2.29) is that it represents a self-similar solution for the adsorption profile. This is illustrated in figure 5.14. 

Another way of thinking about this result draws on the notion we introduced in section 5.1 that the concentration perturbation introduced by the surface decays to the bulk over a distance characterised by the bulk correlation length. For a system such as a symmetrical polymer blend, for which the correlation length is a weak function of the concentration, this leads to an exponential adsorption profile... 

FIGURE 9.1. When a material is positively adsorbed at an interface, its adsorption profile will resemble (a) for a liquid-fluid interface or (b) for a solid-fluid interface. 

For a solution, a higher concentration of the solute near the interface is an indication of positive adsorption of the solute molecules. A typical concentration profile of the adsorbate is shown in Figure 9.8b. From both theoretical and practical standpoints, it is of interest to know the characteristics of such adsorption profiles for a given system in order to understand the mechanism of the adsorption process, as well as its consequences. 

Asare [50-52] studied the adsorption of Cu(H), Ni(II), and Co(II) onto titania, hematite, alumina, and quartz in ammoniacal solutions and found that the conventional sigmoidal adsorption curve was replaced by an adsorption profile that increased initially with increased pH, declined in adsorption as the ammine complexes formed, and then increased at high pH as the hydroxide ligands replaced the ammonia ligands. This effect was also reported by Luo and Huang [53], who studied Cu(H) adsorption onto iron(III), aluminum(Hl), and tin(IV) oxides in ammonia solution for the pH range 5-9. 

The removal, by adsorption, of Cr(III) onto HFO in different solution environments is illustrated in Fig. 8. The four adsorption curves follow the same removal profile, designated as curve 1, indicating that a similar mechanism is operating in all cases. The presence of Ni(II) and/or Zn(II) has little influence over the adsorption profile of Cr(III) onto HFO. This presumably is because the Cr(III) adsorbs at a lower pH than either Ni(II) or Zn(II) and thus the substrate surface, at the pH values of interest, is unaffected. 

Figure 3. CO2 adsorption profiles of hydroxy metal carbonate samples at 316 K up to 175 bars.

Figure 4. Representative adsorption profiles of PLL(10)-g(2.9]-PEG(2) onto (a) silicon oxide and (b) iron oxide substrates as measured by OWLS (buffer solution = lOmM HEPES (pH 7.4), concentration of the polymer = 0.25mg/ml T = 25 C).

Figure 2. Representative adsorption profile for PLL-g-dex copolymer onto a silica-titania waveguide adsorption of the copolymer (PLL(6)-g[5]-dex(5.9)) and subsequent exposure to serum.

Adsorption Properties OWLS. Quantitative Analysis of Polymer Adsorption. Polymer adsorption properties were characterized by means of OWLS. The results of the OWLS experiments (the adsorption profile for PLL(6)-g[5]-dex(5.9) is shown in Eigure 2 as example) indicate that the PLL-g-dex copolymers spontaneously adsorb from aqueous solution (10 mM HEPES buffer, pH 7.4) onto metal oxide surfaces. Upon exposure of a waveguide surface to the polymer solution (after 70 min of exposure to HEPES buffer to achieve the baseline), the adsorption process occurred rapidly, such that more than 90% of the final mass of adsorbed polymer was reached within... 

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