Indication of adsorption

Manheim FX, Pauli, CK (1981) Patterns of ground water salinity changes in a deep continental-oceanic transect off the southeastern Atlantic coast of the U.S.A. J Hydrol 54 95-105 Martin P, Akber RA (1999) Radium isotopes as indicators of adsorption-desorption interactions and barite formation in groundwater. J Environ Radioact 46 271-286 McCarthy J, Shevenell L (1998) Obtaining representative ground water samples in a fractured and karstic formation. Ground Water 36 251-260... 

Adsorption and co-adsorption of ions on the anode are expected to have a bigger influence on product yield when the ion concentrations are comparable and in the low ppm range. Indeed, reports of a different reaction order with respect to chloride oxidation and the influence of sulphate ions (Trassatti 1981) might be an indicator of adsorption effects. The problem is discussed here in terms of analytical errors (Sect. 7.3.3.7). 

Another study examined the NH3 and CO2 adsorption heats on several zirconia catalysts, differing in their preparation procedure and/or in the addition of dopants [46]. The differential heats of NH3 and CO2 adsorption show a wide range of variability, displaying either a plateau of constant heat or a continuous decrease indicative of adsorption heterogeneity [12]. The ratio between the number of the basic and acidic sites, Ub/ua, was calculated for each catalyst from the microcalorimetry results, by dividing the amount of adsorbed CO2 by the amount of adsorbed NH3. These catalysts were used to produce alk-l-ene from 4-methylpentan-2-ol. Alk-1-ene selectivity was found to first increase with the b/Wa ratio, reach a maximum and then decrease, whereas ketone formation continuously increased, being negligible for low Ub/ua values. 

Adsorption on the LL interface can be observed in voltammetric curves, but a more sensitive indication of adsorption can be obtained from impedance measurements. Voltammetric studies (26, 27) showed that the addition of proteins to a so-called blocked (i.e., ideally polarizable) aqueous-nitrobenzene interface resulted in narrowing of the potential window of the supporting electrolyte system. This observation implies that the difference in hydrophilic-hydrophobic properties of the two solvents decreased. This decrease can be explained by postulating the formation of a third phase between the original two. The third phase would allow mediated, easier transport of the supporting electrolyte ions. 

The shape of plots for s against coverage is a further important indicator of adsorption mechanism. The coverage may either be signified in absolute terms by N, the number of adsorbed species cm-2, or by 0, the fraction of sites filled. The use of the latter must be treated with caution it is only unambiguously defined when the number of sites is equal to the number... 

Type 1 isotherms exhibit prominent adsorption at low relative pressures p/po (the relative pressure p/po is defined as the equilibrium v or pressure divided by the saturation vapor pressure) and then level off. Type 1 isotherm is usually considered to be indicative of adsorption in micropores (e.g., adsorption of benzene on microporous active carbon) or monolayer adsorption due to the stror adsorbent-adsorbate interactions (which may be the case for chemisorption, which involves chemical bonding between adsorbate and the adsorbent surface, e.g., adsorption of hydrogen on iron). In the case of nonpolar gases commonly used for charactmzation of porous solids (nitrogen, argon) [10, 12, 13, 17, 56], chemisorption is unlikely and therefore e I reflects usually adsorption on microporous solids. However, type I isotherms may also be observed for mesoporous materials with pore size close to the micropore range. In particular, in the case of adsorption of N2 at 77 K or Ar at both 77 K and 87 K in cylindrical pores, a type I isotherm would have to level off below the relative pressure of about 0.1 for the material to be exclusively microporous, as inferred fi-om tile results of recent studies of siliceous and carbonaceous ordered mesoporous materials (OMM) [57-59]. Consequently, when a type 1 isotherm does not level off below the relative... 

This last effect may be an indication of adsorption of a small impurity in the electrolyte. The inhibited corrosion rates decrease with time and become essentially constant after about two hours. These slopes are not dependent on scan rate or on corrosion rate. The most interesting effect is observed when the inhibited hydrochloric acid solution is aerated the anodic Tafel slope increases while the cathodic Tafel slope decreases dramatically. As would have been expected from the resistance probe measurement the corrosion rate in the aerated inhibitor solution increases. 

Figure 33 depicts a prednisolone calibration curve in dry ACN. The nonlinearity of this profile is obvious. Because there is absolutely no indication of adsorption effects, we hypothesize that there is a following second order chemical reaction. Hydrocortisone gives similar behavior in dry aprotic solvents. Both of these steroids are characterized by an aliphatic alcohol groip which is not associated with the other three ideally behaving steroids. This circumstantial evidence suggests that the anion radical electrode reaction product is being protonated by reactant diffusing toward the electrode. The likelihood that this is the process occurring is further enhanced by the fact that addition of sufficient amounts of a weak proton donor (e.g., H2O) leads to a linear calibration curve with lower sensitivity, as shown in Figure 34. The latter figure illustrates calibration curves for dry and wet ACN and DMF, as well as aqueous base.

The inference is that vacuum treatment has removed blocking molecules from the limited number of nanopores in the unactivated carbon and allowed ingress of deuterated water. Shifts to lower frequencies of adsorbates have been noted for alcohols adsorbed on carbon and have been assigned to the shielding effects of the graphene planes (Harris et al. 1995). These shifts to lower frequency are thus indicative of adsorption processes occurring in the pore system within the bulk of the adsorbent material. 

In summary, the chemistry of the adsorption processes for soluble gold complexes in terms of the surface characteristics of the adsorbing AC remains unresolved but with strong indications of adsorption of metal complexes on graphene layers, rather than ion-exchange of metal cations. 

The refractive index of the film prepared from small, unaged precursors (point A in Fig. 17, hydrodynamic radius -3.0 nm) indicates that the porosity is less than 5% according to Eq. 10. The corresponding nitrogen adsorption-desorption isotherm (Fig. 19) [38] is of Type II and the BET surface area is about 1 cmVcm indicative of adsorption on a nonporous surface. 

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