Adsorption increase

Thus by measuring the small amount of heat 5Q which is evolved when the adsorption increases by the small amount 6n mole at constant temperature, the differential molar energy of adsorption can be evaluated calorimetri-... 

The controhing effect of various ions can be expressed in terms of thermodynamic equhibria [Karger and DeVivo, Sep. Sci., 3, 393 1968)]. Similarities with ion exchange have been noted. The selectivity of counterionic adsorption increases with ionic charge and decreases with hydration number [Jorne and Rubin, Sep. Sci., 4, 313 (1969) and Kato and Nakamori, y. Chem. Eng. Japan, 9, 378 (1976)]. 

AOS 2024 adsorption increases continuously on going from fresh water to 1% NaCl to 4% NaCl. Aqueous 1% NaCl was studied as an analog to aqueous 1% sodium sulfate. The last two entries of Table 19 show that increased AOS 2024 adsorption in the presence of sodium sulfate could mitigate any reduction in calcium ion-promoted surfactant precipitation. However, the larger than usual experimental uncertainty in the sodium sulfate results means that the... 

Typical adsorption isotherms are shown in Figs. 16 and 17. Despite the large experimental scatter, a steep increase in adsorption can be seen at low concentrations, followed by a plateau at concentrations exceeding the CMC. Similar behavior has been observed before with model surfactants [49-54] and has also been predicted by modem theories of adsorption [54]. According to Fig. 16, adsorption increases modestly with salinity provided that the calcium ion concentration remains low. The calcium influence, shown in Fig. 17, cannot be explained by ionic strength effects alone but may be due to calcium-kaolinite interactions. 

Another case study supporting the AX hydrophilicity scale is the adsorption of terminal diols. Figure 28 shows that adsorption on Au911 is weaker than on Hg912 as expected, while adsorption increases with the number of carbon atoms almost in parallel for the two metals. It is intriguing that the adsorption of 1,4-butanediol at the air/solution interface is weaker than on Hg328 and is of the same order of magnitude as on Au. 

For alkali modified noble and sp-metals (e.g. Cu, Al, Ag and Au), where the CO adsorption bond is rather weak, due to negligible backdonation of electronic density from the metal, the presence of an alkali metal has a weaker effect on CO adsorption. A promotional effect in CO adsorption (increase in the initial sticking coefficient and strengthening of the chemisorptive CO bond) has been observed for K- or Cs-modified Cu surfaces as well as for the CO-K(or Na)/Al(100) system.6,43 In the latter system dissociative adsorption of CO is induced in the presence of alkali species.43... 

Chitosan samples with degrees of deacetylation of 65,73,85, and 92% were almost completely adsorbed onto the surfaces of cellulosic fibers, especially onto the surfaces of fines in a variety of cellulosic systems used in industrial operations. Adsorption increased as the degree of deacetylation of chitosan increased. The aggregation of the fine cellulosic particles was maximum at a dosage of about 10 mg/kg. The interactions between chitosan and the cellulosic substrates were dominated by a bridging mechanism at about pH 7 [32]. 

The equilibrium time required for adsorption of metals on biomass was studied for various initial metal concentrations and the results were shown in Figure 2. The adsorption increases rapidly with time in the initial period of adsorption and approaches an equilibrium at about 120min for all the concentrations studied (10-100 mg/L). The slow but gradual increase of metal biosorption after 120min indicates that the adsorption occurs through a continuous formation of adsorption layer in the final period of adsorption. 

The amoimt and strength of hydrogen adsorption changed with the adsorption temperature for all catalysts examined. As the adsorption temperature was raised, the amount and strength of adsorption increased. 

Similar results were found in a study of aromatic carboxylates with one to six carboxyl groups (Scott, Jackson Wilson, 1990). Adsorption increased with the number of carboxyl groups and was also dependent on the spacing between the carboxyl groups. With the benzene dicarboxylates, maximum permanent adsorption was obtained with the 1,3-dicarboxylate, while the 1,4-dicarboxylates was not adsorbed at all. This is again evidence of the cooperative effect between carboxyl groups. 

The capacity of an adsorbent to adsorb an adsorbate can be represented by adsorption isotherms, as shown in Figure 10.7a, or adsorption isobars, as shown in Figure 10.7b. The general trend can be seen that adsorption increases with decreasing temperature and increases with increasing pressure. 

The adsorption of HPAM on sand (Figure 4) is not detected below a threshold value of Ca2+ due to strong electrostatic repulsion between the polyelectrolyte and the highly charged negative surface. This threshold value, which was also observed in the case of monovalent ions (9), represents the point where the critical adsorption energy is overcome, and once this value is surpassed, adsorption increases sharply. This form of adsorption behavior is in line with predictions of theories on polyelectrolyte adsorption (20). 

In groundwater, hexavalent chromium tends to be mobile due to the lack of solubility constraints and the low adsorption of CH6 anion species by metal oxides in neutral to alkaline waters (Calder 1988). Above pH 8.5, no CH6 adsorption occurs in groundwater Cr adsorption increases with decreasing pH. Trivalent chromium species tend to be relatively immobile in most groundwaters because of the precipitation of low-solubility Cr 3 compounds above pH 4 and high adsorption of the Cr+3 ion by soil clay below pH 4 (Calder 1988). 

The adsorption of fatty acids on the non-polar hydrophobic surface (Hg) is dominated by their hydrophobic properties. The extent of adsorption increases with increasing chain length. The following relationship of the free energy of adsorption, AGacis. and the number of C atoms, nc, of the fatty acids can be established ... 

Free energy variations with temperature can also be used to estimate reaction enthalpies. However, few studies devoted to the temperature dependence of adsorption phenomena have been published. In one such study of potassium octyl hydroxamate adsorption on barite, calcite and bastnaesite, it was observed that adsorption increased markedly with temperature, which suggested the enthalpies were endothermic (26). The resulting large positive entropies were attributed to loosening of ordered water structure, both at the mineral surface and in the solvent surrounding octyl hydroxamate ions during the adsorption process, as well as hydrophobic chain association effects. 

The adsorptive effects of the polar adsorbents are often due to the presence of hydroxyl groups and the formation of hydrogen bonds with the solute molecules. The strength of these bonds and hence the degree of adsorption increases as the polarity of the solute molecule increases. In order to separate the solute from the adsorbent it is necessary to use a solvent in which the solute will dissolve and which also has the ability to displace the solute from the adsorbent. Solvents that are too polar will overwhelm the adsorptive effects and result in the simultaneous elution of all the components of a mixture. Table 3.3 lists various classes of compounds and some common solvents in order of polarity. 

Figure 28.5 displays the effect of changing initial concentration of Cu " from 10 to 100 pg luL on the rate of adsorption. Increasing the initial concentration increases the competition of Cu " ions molecules at the active site of the adsorbent and as a result more Cu + adsorbed per gram of leaves. 

Before analysis of semi- or nonvolatile components can proceed, it is necessary that the hydrocarbon components be brought into solution. In a sample from a contaminated site, semi- and nonvolatile molecules may exist in the soil pores in the free form within the pore spaces, but are far more likely to be adsorbed by organic matter attached to the soil. Indeed, the probability of such adsorption increases with increasing hydrophobicity of the molecules. 

DDTC is an organic anion with comparatively big e and variable shape. After adsorption and bonding with mineral electrode, it can be effectively close to the electrode surface so that / becomes small and e becomes big. So its capacitance increases with the DDTC concentration added, amount of adsorption increasing. 

Bobka (144) studied the adsorption of diphenylguanidine on graphite wear dust. As was shown by Rivin (85), diphenylguanidine adsorption is equivalent to NaHCOj neutralization in the determination of carboxyl groups. With increasing grinding time, surface area and diphenylguanidine adsorption increased parallel to each other. 

Metal cation adsorption processes include exchange, Coulombic, and site-specific adsorption. Heavy metal cations exhibit exchange reactions with negatively charged surfaces of clay minerals. Cationic adsorption is affected by the pH and in an acid environment (pH < 5.5), and some heavy metals do not compete with Ca " (a ubiquitous constituent in the subsurface) for mineral adsorption sites. At a higher pH, heavy metal adsorption increases abruptly and becomes irreversible. 

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