Additive adsorption

Renewed Sn + Cd alloy surfaces have been studied by Safonov and Choba821 by impedance. The has been found to shift toward more negative E with time, suggesting that the content of Cd at the Sn + Cd alloy surface increases with time. For the alloy with 10% Cd, the time dependence of C for adsorption of organic substances is significantly different from that for Sn + Pb alloys. At relatively short times, E"1 shifts in the negative direction, which shows the increase of the Cd content in the Sn + Cd alloy surface layer. At longer times, an additional adsorption-desorption peak (step) has been observed, which has been explained by the formation of rather wide two-dimensional areas of Cd microcrystals at the alloy surface.824... 

Zhang J, Manglik RM (2005) Additive adsorption interfacial characteristics of nucleate pool boiling in aqueous surfactant solutions. J Heat Transfer ASME 127 684-690... 

Additional adsorption sites are provided on open metal sites, when available. [Cu3(BTC)2] is performant in the selective adsorption and separation of olefinic compounds. The highly relevant separations of propene from propane and of isobutene from isobutane have been accomplished with separation factors of 2.0 and 2.1, respectively [101, 102]. [Cu3(BTC)2] also selectively takes up pentene isomers from aliphatic solvent in liquid phase, and even discriminates between a series of cis- and trans-olefin isomer mixtures with varying chain length, always preferring a double bond in cis-position. This behavior is ascribed to tt -complexation with the open Cu sites [100]. 

Increased concentration of PSS at 7.0 g/L (1.4 X 10 M) leads to an increase in the force to value seven higher than that between the surfaces of fluorocarbon monolayers alone. The origin of this force is electrostatic in nature. Recharging of the surface by additional adsorption of PSS should occur as shown in Figure 9b. 

MgO at a temperature above 50 C, no additional adsorption is recorded at all, though the efficiency of singlet oxygen de-excitation on magnesium oxide is close to unity. 

Data used for the design of adsorption processes are normally derived from experimental measurements. The capacity of an adsorbent to adsorb an adsorbate depends on the compound being adsorbed, the type and preparation of the adsorbate, inlet concentration, temperature and pressure. In addition, adsorption can be a competitive process in which different molecules can compete for the adsorption sites. For example, if a mixture of toluene and acetone vapor is being adsorbed from a gas stream onto activated carbon, then toluene will adsorbed preferentially, relative to acetone and will displace the acetone that has already been adsorbed. 

Additional adsorption studies were also carried out using para- and ortho-chlorobenzaldehydes (Figure 4). The results obtained with p-chlorobenzaldehyde are very similar to the ones obtained with m-clilorobenzaldehyde and were omitted from this paper for brevity. In contrast, substantial differences are observed in the spectra of adsorbed o-chlorobenzaldehyde. In particular, in this case the 1620 cm"1 band characteristic... 

This is considered to be largely a qualitative technique. Difficulties that arise in obtaining reproducible quantitative data are similar to those encountered in thin-layer chromatography. In addition, adsorption characteristics of dyes on macromolecules are so variable that only semiquantitative comparisons can be made. These are, however, still very useful... 

The oxygen vacancies created according to Eq. (2.4) act as additional adsorption sites for oxygen, which increases the concentration of adsorbed oxygen and results in a larger resistance change. 

Note that the product /A yields the scan rate of the square-wave potential modulation. If the delay period is sufficiently long, the additional adsorption during the potential scan is negligible. Otherwise, the additional adsorption complicates the theoretically expected dependencies, in particular the relationships between the net peak currents and potentials on the frequency [114]. 

Structure of the double layer, including concentration of different species present in the solution. The pKJtential dependence of additive adsorption and their effects on growth forms are discussed in Chapter fO. 

Water-reducing admixtures are not adsorbed equally by the various anhydrous and hydrated cement constituents and in studies with calcium lignosulfonate, the approximate maximum adsorption figures shown in Table 1.5 have been obtained [38,39], In addition, adsorption isotherms have been studied at various ages of C3A hydration [36] and it has been shown that it is the initial hydration products (less... 

UPD of various metal ions is accompanied by the adsorption of anions. Evidently, such additional adsorption makes stoichiometric calculations based on the determined charge value misleading. 

Type I isotherms are encountered when adsorption is limited to, at most, only a few molecular layers. This condition is encountered in chemisorption where the asymptotic approach to a limiting quantity indicates that all of the surface sites are occupied. In the case of physical adsorption, type I isotherms are encountered with microporous powders whose pore size does not exceed a few adsorbate molecular diameters. A gas molecule, when inside pores of these small dimensions, encounters the overlapping potential from the pore walls which enhances the quantity adsorbed at low relative pressures. At higher pressures the pores are filled by adsorbed or condensed adsorbate leading to the plateau, indicating little or no additional adsorption after the micropores have been filled. Physical adsorption that produces the type I isotherm indicates that the pores are microporous and that the exposed surface resides almost exclusively within the micropores, which once filled with adsorbate, leave little or no external surface for additional adsorption. 

Type III isotherms are characterized principally by heats of adsorption which are less than the adsorbate heat of liquefaction. Thus, as adsorption proceeds, additional adsorption is facilitated because the adsorbate interaction with an adsorbed layer is greater than the interaction with the adsorbent surface. 

Specific surface areas of the materials under study were calculated using the BET method [22, 23]. Their pore size distributions were evaluated from adsorption branches of nitrogen isotherms using the BJH method [24] with the corrected form of the Kelvin equation for capillary condensation in cylindrical pores [25, 26]. In addition, adsorption energy distributions (AED) were evaluated from submonolayer parts of nitrogen adsorption isotherms using the algorithm reported in Ref. [27],... 

There is a substantial body of theoretical work on micellization in block copolymers. The simplest approaches are the scaling theories, which account quite successfully for the scaling of block copolymer dimensions with length of the constituent blocks. Rather detailed mean field theories have also been developed, of which the most advanced at present is the self-consistent field theory, in its lattice and continuum guises. These theories are reviewed in depth in Chapter 3. A limited amount of work has been performed on the kinetics of micellization, although this is largely an unexplored field. Micelle formation at the liquid-air interface has been investigated experimentally, and a number of types of surface micelles have been identified. In addition, adsorption of block copolymers at liquid interfaces has attracted considerable attention. This work is also summarized in Chapter 3. 

Once the negative charges on the particle surface have been neutralised further adsorption of the surfactant occurs via the tail on to the hydrophobic patches of the surface and also by association of the hydrocarbon chains. Detailed adsorption studies have been reported on polystyrene latices (36). The additional adsorption provides a positive charge to the particles and restabilization occurs.. The sterpnasa of this phenomenon is... 

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