Electrostatic adsorption

The dyeing process provides for temporary, semipermanent (direct dyes), and oxidation-type reactions (semipermanent or permanent colors). It may involve absorption or adsorption (electrostatic) of the colorant into/to the hair structure, bleaching or otherwise masking the natural melanin col-... 

The numerical values of log K obtained for the TLM model (Fig. 5.85, Table 5.19) combined with different models of Pb adsorption (electrostatic position of Pb, number of proton released per one adsorbed Pb), are summarized in Table 5.26. 

The discussed above examples are limited to adsorption of divalent metal cation. They indicate that the numerical value of the stability constant of the surface complex depends on the assumed model of primary surface charging. In this respect the significance of comparison of the stability constants of analogous surface complexes from different sources is questionable, when these stability constants were calculated using different models of primary surface charging. On the other hand the choice of the model of primary surface charging has rather limited effect on the shape of the calculated uptake curves. The shape of calculated uptake curves (slope, ionic strength effect) and the numerical value of the stability constant of the surface complex are both affected by the model of specific adsorption (electrostatic position of the specifically adsorbed cation and the number of protons released per one adsorbed cation). 

However, the possibilities to adjust the course of model uptake curves by the selection of the simple model of specific adsorption (electrostatic position and the number of protons released per one specifically adsorbed cation or per one molecule of weak acid) are limited. It should be emphasized that the CD model was introduced quite recently, and in most publications summarized in Tables 4.1 and 4.2 only the choice between two electrostatic positions (inner- and outer-sphere) was considered. Thus, the ability to find a simple model properly simulating the actual uptake curves was even more limited than nowadays. But even when the charge distribution concept is taken into account, it often happens that the simple models fail to properly reflect the experimentally observed effects of the pH and ionic strength on the specific adsorption. This problem has been solved by... 

The main principles of separation are adsorption (electrostatic forces), partition (solubility), and ion exchange (charge). Information on the theoretical background of TLC is presented elsewhere (Miller 2004). Depending on the movement of the mobile phase, TLC may be ascending or descending in the nuclear medicine laboratory, ascending TLC is the method of choice (Robbins 1983). 

The consensus is that organic compounds inhibit corrosion by adsorbing at the metal/solu-tion interface. Three possible types of adsorption are associated with organic inhibitors n-bond orbital adsorption, electrostatic adsorption, and chemisorptions. A more simplistic view of the mechanism of corrosion inhibitors can be described as controlled precipitation of the inhibitor from its environment (water and hydrocarbons) onto metal surfaces. During the past decade, the primary improvements in inhibitor technology have been the refinement of formulations and the development of improved methods of applying inhibitors (Totlani and Athavale 2000 Farquhar et al. 1994). 

If one reconsiders the case of pH lower than the PZC of Ti02 (conditions of anion adsorption), electrostatic adsorption of the gold anions is possible. However, the increasing gold uptake when pH increases is not consistent. The presence of neutral AuCl3(H20) between pH 2 and 5 deduced from thermodynamic data, which may interact with the support, could explain that the gold uptake increases as pH increases and becomes closer to the PZC. Literature data in geochemistry reports the same type of observation, that is... 

The isoelectric points (iep s) of the two substrates used in this study were measured [25] by using a DELS A 440 and found to be at pH 8.2 for HFO and at pH 9,2 for HCO. Both Ni(II) and Zn(II) are completely adsorbed at pH values considerably less than either of these values (see Sec. HI, Figs. 3-51, indicating that the surface is positively charged during adsorption. Electrostatic forces, in this case, are unfavorable to adsorption, and there must be a strong specific interaction for adsorption to occur. 

The noncovalent bonding methods mainly indude adsorption, electrostatic interaction, and encapsulation, as illustrated in Scheme 10.8 [51], The simple physisorption... 

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