Adsorption decrease

If an ionic surfactant is present, the potentials should vary as shown in Fig. XIV-5c, or similarly to the case with nonsurfactant electrolytes. In addition, however, surfactant adsorption decreases the interfacial tension and thus contributes to the stability of the emulsion. As discussed in connection with charged monolayers (see Section XV-6), the mutual repulsion of the charged polar groups tends to make such films expanded and hence of relatively low rr value. Added electrolyte reduces such repulsion by increasing the counterion concentration the film becomes more condensed and its film pressure increases. It thus is possible to explain qualitatively the role of added electrolyte in reducing the interfacial tension and thereby stabilizing emulsions. 

At low adsorbate loadings, the differential heat of adsorption decreases with increasing adsorbate loadings. This is direct evidence that the adsorbent surface is energetically heterogeneous, ie, some adsorption sites interact more strongly with the adsorbate molecules. These sites are filled first so that adsorption of additional molecules involves progressively lower heats of adsorption. 

For Sn(IV) adsorption a value of around 4 is reached at potentials below 0.25 V indicating the reduction to Sn(0). As the adsorption potential is made more positive the number of charges for tin adsorption decreases, indicating that increasing amounts of Sn(II) species are formed. Above 0.6 V, n < 2 indicates that tin is partially adsorbed as a mixture of Sn(II) and Sn(IV). 

Adsorption on Kaolinite. For kaolinite, the polymer adsorption density is strongly dependent on the solid/liquid ratio, S/L, of the clay suspension. As S/L increases, adsorption decreases. This S/L dependence cannot be due totally to autocoagulation of the clay particles since this dependence is observed even in the absence of Ca2+ at pH 7 and at low ionic strength where auto-coagulation as measured by the Bingham yield stress is relatively weak (21). Furthermore, complete dispersion of the particles in solvent by ultra-sonication before addition of... 

The influence of Ca2+ on the variations of adsorption with the degree of ionicity of HPAM on sand at pH 7 in 2 g/1 NaCl is given in Figure 9. Without calcium, adsorption decreases with polymer charge because of the increase in... 

Dang et al. (1994) observed that the experimentally determined solubility lines for Zn2+ in 14 soil solutions from southern Queensland with soil pH from 7.45-8.98 and 0.08-2.07% CaC03 were not undersaturated with respect to the solubility of any known mineral form of Zn. Therefore, they suggested that Zn2+ activity was mainly controlled by adsorption-desorption reactions in these soils. Similar observation on solubility of Cr(VI) in arid soils was reported by Rai et al. (1989). In the absence of a solubility controlling solid phase, Cr(VI) aqueous concentrations under slightly alkaline conditions may be primarily controlled by adsorption/desorption reactions (Rai et al., 1989). Chromuim(VI) is adsorbed by iron and aluminum oxides, and kaolinite and its adsorption decreases with increasing pH. 

When the coverage of CO (and many other gases) on surfaces reach a critical point, it has been found that the heat of adsorption decreases rapidly. What could be the explanation for this behavior ... 

Adsorbents (Activated carbons and charcoals) Large adsorption capacity for VOCs and odors Immediately noticeable effects Operates wall avuri uniter vary humid uundiliuris. Inefficient for removing tow molecular weight pollutants such as formaldehyde end ammonia, Adsorption decreases rapidly with time snd frequent ruplautmerit is requited. 

There have been many investigations into the behaviour of plutonium in soil (32-37). In laboratory studies Rhodes (33) has demonstrated that the adsorption of trace quantities of plutonium onto soil particles was pH dependent. Over the pH range 2 to 8, approximately 98-100% of the plutonium was adsorbed from aqueous solution but in the range pH 8—12 the adsorption decreased to 80%. On the basis of ultrafiltration studies Rhodes concluded that the trace quantities of plutonium were polymerising at pH2 and above to give positively charged polymers, (Pu(OH)+)n, which... 

The linear equilibrium isotherm adsorption relationship (Eq. 11) requires a constant rate of adsorption, and is most often not physically valid because the ability of clay solid particles to absorb pollutants decreases as the adsorbed amount of pollutant increases, contrary to expectations from the liner model. If the rate of adsorption decreases rapidly as the concentration in the pore fluid increases, the simple Freundlich type model (Eqs. 8 and 9) must be extended to properly portray the adsorption relationship. Few models can faithfully portray the adsorption relationship for multicomponent COM-pollutant systems where some of the components are adsorbed and others are desorbed. It is therefore necessary to perform initial tests with the natural system to choose the adsorption model specific to the problem at hand. From leaching-column experimental data, using field materials (soil solids and COMs solutions), and model calibration, the following general function can be successfully applied [155] ... 

The AG° values of acetone adsorption decrease slightly in the sequence H2O,Me0H, NM. They are indicative of a weak physical adsorption at the Hg/solution interface. It is also evident that the Gibbs energy of adsorption is enhanced by the electric field, particularly at the point of adsorption maximum. Small values of AG , similar to those determined at the solution/air interface, attest to the absence of specific interactions cf acetone with the mercury surface (which is opposite to the TU adsorption case). Hence, the solute-solvent interaction in the solution is an important factor in the adsorption of acetone, as shown for the zero charge on the Hg electrode in Fig. 11. 

Surface diffusion has been extensively studied in literature. An overview of experimental data is given in Table 6.1. Okazaki, Tamon and Toei (1981), for example, measured the transport of propane through Vycor glass with a pore radius of 3.5 nm at 303 K and variable pressure (see Table 6.1). The corrected gas phase permeability was 0.69 m -m/m -h-bar, while the surface permeability was 0.55 m -m/m -h-bar, and so almost as large as the gas phase permeability (Table 6.1). It is clear from Table 6.1, that the effects of surface diffusion, especially at moderate temperatures, can be pronounced. At higher temperatures, adsorption decreases and it can be expected that surface diffusion will become less pronounced. 

Dlnoseb has a reported Kq, of 124 (20) but no was given. The adsorption of dlnoseb on montmorrllonlte and llllte clays with Increasing pH resembles Its pH-tltratlon curve adsorption decreases with Increasing pH until there Is little. If any, adsorption when the pesticide Is In Its anion form (90). 

Relative adsorphon affinities of different funchonal groups on the ambient-exposed Cu films have been determined by immersing the films in THF solutions containing two differently-functionalized organic molecules. Their preferential adsorption decreased in the order -NC[l,4-C,sH4(NC)2] -SH[1,4-... 

The reduction of silver chloride, precipitated in the presence of excess chloride ion, yielded the S-shaped curve typical of an autocatalyzed reaction (James, 25). The initial reaction rate, measured in terms of the reciprocal of the time required to complete 5 % of the total reaction, varied directly as the hydroxylamine concentration and inversely as the chloride ion concentration when the latter was relatively large. The specific surface of the freshly prepared precipitate, as measured by dye adsorption, decreased with aging, and the reaction rate decreased proportionately. 

In this section a method for the direct calorimetric determination of heats of adsorption on evaporated metal films is described and results for the heals of adsorption of hydrogen on nickel, iron, and tungsten are reported. In all cases the heats of adsorption decrease with the fraction of surface covered in a mode that can satisfactorily be explained by interaction of adsorbed atoms. A criterion for mobility of the adsorbed atoms is developed... 

In acidic media, the extent of adsorption of para-substituted benzoic acid on ferri-hydrite and goethite depends on the nature of the substituent (Rung and McBride, 1989). Adsorption decreases in the order ... 

To date, only the second form of ternary adsorption has been observed for iron oxides. Davis and Leckie (1978 a) found that thiosulphate adsorbed on ferrihydrite in acid media with adsorption decreasing to zero as the pH rose to ca. 7, whereas the adsorption edge of silver lay between pH 7 and 8. In the presence of thiosulphate, adsorption of silver was enhanced in the pH range 4-6.5 (Fig. 10.10), i. e. 

The amphoteric indium oxide can be considered as more basic than acidic when comparing the adsorption heats and irreversible adsorbed amounts, which are clearly higher for SO2 adsorption than for ammonia adsorption [40,47]. The heats of NH3 adsorption decreased continuously with coverage, while the SO2 adsorption heat remained constant over a wide range of coverage. 

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