Surface adsorption affinity

A plot of C/-SC versus C will produce a straight line with slope 1/ST and y intercept of 1/KlSt (Fig. 4.21). Such a plot will allow one to determine the so-called adjustable parameters, ST and KL. Note that both the Freundlich equation and the Langmuir equation produce a surface adsorption affinity constant, but the latter (Langmuir) also produces the often-sought adsorption maximum (ST). 

Certain negative ions such as Cl , Br, CNS , N03 and SO2 show an adsorption affinity to the mercury surface so in case (a), where the overall potential of the dme is zero, the anions transfer the electrons from the Hg surface towards the inside of the drop, so that the resulting positive charges along the surface will form an electric double layer with the anions adsorbed from the solution. Because according to Coulomb s law similar charges repel one another, a repulsive force results that counteracts the Hg surface tension, so that the apparent crHg value is lowered. 

The metal virtually always possesses [even in the purest forms known today (99.9999%)] a microheterogeneity of the surface with respect to the ease of oxidation or the adsorption affinities for various species. 

Since many metallic catalysts have high adsorption affinities, we often find that certain poison molecules are adsorbed in an immobile form after only a very few collisions with the catalyst surface. In this situation, the outer periphery of the catalyst particle will be completely poisoned while the inner shell will be completely free of poison. The thickness of the poisoned shell grows with prolonged exposure to poison molecules until the pellet is completely deactivated. During the poisoning process, the boundary between active and deactivated regions is relatively sharp. 

At present, a wide range of solid substrates are available for protein immobilization. According to the protein attachment strategies, namely, adsorption, affinity binding, and covalent binding, all these substrates can be separated into three main parts. Surfaces like ploy(vinylidene fluoride) (PVDF), poly(dimethylsiloxane) (PDMS), nitrocellulose, polystyrene, and poly-1-lysine coated glass can adsorb proteins by electrostatic or hydrophobic forces. A potential drawback of such substrates is the difficulty... 

Figure 9 shows adsorption isotherms for this protein on the various sorbents. As is usually observed for proteins at surfaces, the adsorption affinity is higher for the hydrophobic surfaces than for the hydrophilic ones. The adsorption plateau-values at silica and PS- (EO)8, approximately... 

The conversion of parathion is affected by soil constituents in the order kaolinite > smectite > organic matter and is related inversely to the adsorption affinity of these materials for this contaminant (Mingelgrin and Saltzman 1977). Although the extent of hydrolysis differs among soils, it is apparent that soil-surface degradation of parathion is caused by hydrolysis of the phosphate ester bond. The presence of water in the soil-parathion system led to a decrease in the surface-induced degradation of the organic molecule and diminished the effect of natural soil properties on its persistence. 

Equation (2) predicts that the concentration of adsorbed sample molecules is decided by the difference between adsorptive affinities of the sample and developer molecules onto the adsorbent surface and this is just the same as the aforementioned statement that the rate of sample migration is decided by a competitive balance of the interactions [A D] and [A-P]. On the other hand, the distribution coefficient K° is related to the Rf value by... 

Affinity Adsorption Affinity adsorption is based on the chemical interaction between a solute and a ligand which is attached to the surface of the carrier particle by covalent or ionic bonds. The principle is illustrated in Figure 10.7. 

A similar argument [7] was presented by Muller et al. [227] in their incisive analysis of adsorption of weak electrolytes from aqueous solution on ACs The solid surface charges in response to solution pH and ionic strength the resulting (smeared) surface electrostatic potential influences the adsorption affinity of the ionized solute. ... 

The method of the investigation of the distribution of the H+ ion adsorption affinity to metal oxide surface, allows to establish the reaction constants for the discrete and continuous distribution [135]. Numerical results of the fitting so far obtained, do not allow us to judge which is the better method, that is, which one better determines the real energetic distribution of adsorption sites. After all, because of the good fitting of the data, they are very useful in determining the distribution of the components between solution and the solid, even in the composed systems. 

The low affinity of the surface of pure carbon for water is associated with the unusually weak non-specific interactions between the non-polar surface and the adsorbate. When certain functional groups are present on the carbon surface, specific interactions come into play and the adsorption affinity is thereby increased (see Chapter 1). 

Manganese oxides have a high affinity for many of the trace metals.5 6 In addition to surface adsorption, trace metals accumulate in Mn oxides by substitution and coprecipitation.7 The adsorptive properties of Mn oxides for metals observed in the laboratory are verified in soils, as Mn oxide nodules separated from soils contain concentrations of trace metals that are considerably greater than the metal concentrations in the bulk soil.7 8 The potential for association of trace metals with Mn oxides via co-precipitation or substitution is high when soils are subject to alternate wetting and drying cycles,9 and Mn oxide crystals are forming. 

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