Associative adsorption

Selective Adsorption Associates Inc. Specialists in adsorption and filtration products offering assistance in client to product applications. 

As indicated in Box 3.1, the ability (or inability) of a given compound to undergo specific interactions can be used to divide organic chemicals into different categories. This classification will ultimately be useful when we want to determine whether we should include various factors for quantifying the contributions of these forces in our estimates of the energies controlling specific absorption or adsorption associations in which we are interested. 

The Gibbs representation provides a simple, clear-cut mode of accounting for the transfer of adsorptive associated with the adsorption phenomenon. The same representation is used to define surface excess quantities assumed to be associated with the GDS for any other thermodynamic quantity related with adsorption. In this way, surface excess energy (U°), entropy (Sa) and Helmholtz energy (Fa) are easily defined (Everett, 1972) as ... 

Associative adsorption Dissociative adsorption Associative adsorption Dissociative adsorption... 

The dissociative adsorption - associative desorption type of reaction also takes place when Ln or An trichlorides are chemically volatilized into the carrier gas containing a rather large concentration of A12C16 vapors. Chromatography evidently proceeds due to the equilibria like ... 

The published evidence is overwhelmingly supportive of the redox mechanism,although some authors still favor the adsorptive (associative) mechan-The existing discrepancy in conclusions... 

Adsorption requires the O2 molecule to find a pair of adsorption sites and desorption requires two adsorbed G atoms to be adjacent. Hill [15] and Kisliuk [18,19] discuss lattice statistics and the probability of find-Ing pairs of sites in two-dimensional arrays presented by the regular arrangement of surface atoms illustrated in Figure 5.16. Boudart and pjega-Mariadassou [3],and Hayward andTrapnell [13], describe how the probability of finding pairs of sites is used to develop rate expressions on surfaces. When a bimolecular surface reaction occurs, such as dissociative adsorption, associative desorption, or a bimolecular surface reaction, the rate in the forward direction depends on the probability of finding pairs of reaction centers. This probability, in turn, depends... 

Adsorption eind desorption characteristics of the protein cytochrome c onto ordered mesoporous silicates are detailed. The amount of adsorption is related to the characteristics of the mesopore dieuneter with most adsorption associated with materials having pore diameters in excess of the size of cytochrome c. Adsorbed protein did not desorb with repeated washing in buffer but polyethylene glycol and/or ammonium sulphate in buffer caused considerable desorption. 

Tomasic, V., Stefanic, I., and Filipovic-Vincekovic, N., Adsorption, association, and precipitation in hexadecyltrimethylammonium bromide/sodium dodecyl snlfate mixtures. Colloid Polym. Sci, 277, 153-163 (1999). 

Temperature can also alter wettability by affecting either the surfactant or the surfactant-surface adsorption characteristics. Ziegler et al. [69] reported that the adsorption of a nonionic (nonylphenoxypolyethanol) decreased with temperature increase for low concentrations, whereas the opposite was true for high concentrations. Noll et al. [66] reported adsorption calorimetry results that indicated an increase in temperature decreased adsorption for sodium dodecylsuUate (anionic) and decyltrimethy-lammonium bromide (cationic) surfactants regardless of surface wettability. Similar results were reported for nonionic commercial surfactant (Triton X-100) except for adsorption on an oil-wet surface. These trends were eonsistent with an increase in adsorption associated with conditions that caused a decrease in surfactant solubility in solution. 

In the case of HM-polymers abundant evidence exists that the alkyl groups in the dissolved polymer can be preassociated. This means that centers will be provided for the adsorption/association of surfactant ions (and molecules). Their composition and size will change with surfactant concentration, as will their nature—intermolecular and/or intramolecular. Fine points in this case include the number, type, chain length, and distribution of hydrophobic groups and, again, the detailed structure of the base polymer. In fact, the number of possible variations on this structural theme is vast ... 

The balance between hydrophilic and hydrophobic part of the chain (sometimes referred to as the hydrophilic lipophilic balance, HLB) gives these molecules their special properties Accumulation at various interfaces (adsorption) association in solution to form micelles. 

Luntz AC, Persson M (2005) How adiabatic is activated adsorption/associative desorption J Chem Phys 123 074704... 

---