Adsorption of compound

Separation of milled solid materials is usually based on differences in their physical properties. Of the various techniques to obtain ore concentrates, those of froth flotation and agglomeration exploit differences in surface activities, which in many cases appear to involve the formation of complexes at the surface of the mineral particles. Separation by froth flotation (Figure 4) depends upon conversion of water-wetted (hydrophilic) solids to nonwetted (hydrophobic) ones which are transported in an oil-based froth leaving the undesired materials (gangue) in an aqueous slurry which is drawn off from the bottom of the separator. The selective conversion of the ore particles to hydrophobic materials involves the adsorption of compounds which are usually referred to as collectors. 4... 

Various sample enrichment techniques are used to isolate volatile organic compounds from mammalian secretions and excretions. The dynamic headspace stripping of volatiles from collected material with purified inert gas and trapping of the volatile compounds on a porous polymer as described by Novotny [3], have been adapted by other workers to concentrate volatiles from various mammalian secretions [4-6]. It is risky to use activated charcoal as an adsorbent in the traps that are used in these methods because of the selective adsorption of compounds with different polarities and molecular sizes on different types of activated charcoal. Due to the high catalytic activity of activated charcoal, thermal conversion can occur if thermal desorption is used to recover the trapped material from such a trap. 

Combinations of Bi203 and Mo03, promoted by P2Os at a constant P/Mo ratio (0.2) were studied over a full composition range by Ai and Ikawa [6], Acidity (and basicity) were measured directly by adsorption of compounds like ammonia, pyridine and acetic acid. The effect of the Bi/Mo ratio on the acidity (Fig. 14) parallels the effect on the overall butene oxidation activity [presented in Fig. 5, Sect. 2.3.2(a)(i)]. 

The total number of drugs eluted from KOH-treated phases is less than the number eluted from similar phase nontreated coluims. The KOH treatment is done to reduce the adsorption of compounds by the support phase, and although it does this well, it also prevents the elution of phenolic base drugs such as morphine because of conversion to nonvolatile potassium phenolates. Many higher molecular weight alkaloids become thermolabile under such alkaline conditions and do not elute. Non-KOH treated phases have less tendency to cause such decomposition. 

Figure 3.43. Use of tetrabenzofluorene derivatives for the reversible adsorption of compounds on charcoal [852],...

The NIOSH methods, in general, are based on adsorption of compounds in the air over a suitable adsorbent, desorption of the adsorbed analytes into a desorbing solvent, and, subsequently, their determination by GC using a suitable detector. A known volume of air is drawn through a cartridge containing coconut shell charcoal. The adsorbed compounds are desorbed into carbon disulfide, propanol, benzene, toluene, hexane, or methylene chloride. An aliquot of the solvent extract is then injected onto the GC column. FID is the most commonly used detector. Other detectors, such as ECD, ELCD, or PID have been used, however, in the method development of certain compounds. NIOSH method numbers and the analytical techniques are presented in Table 2.9.3. 

Figure 2. The effect of PEG-modification on the lignin model compound, dehydro-diisoeugenol (dimer). Solvent = acetonitrile, t =0 is the brightness recorded immediately after adsorption of compound on filter paper. The brightness of untreated filter paper is 80.1%. (Cole, B.J.W. Huth, S.P. Runnels, P.S., /. Wood Chem. Technol., in press.)...

Groszek, A.J., Preferential Adsorption of Compounds with Long Methylene Chains on Cast Iron, Graphite, Boron Nitride and Molybdenum Disulfide, ASLE Trans., 9, 67, (1996). 

Neutron reflectometry has been applied to the study of a variety of surfaces, including solid polymeric films, ferromagnetic films, and pure liquid surfaces (Penfold and Thomas, 1990). The technique has also been used in conjunction with Langmuir film balance apparatus to study the adsorption of compounds at the air-water interface, e.g., alkyl trimethylammonium bromide surfactants (Lee et al., 1989), fatty acids (e.g., Grundy et al., 1988), and a variety of polymeric compounds (e.g., Henderson et al., 1991 Henderson, 1993). 

The activated carbon produced is graded, screened, and de-dusted. Activated carbons produced by steam activation generally exhibit a fine pore structure, ideal for the adsorption of compounds from both the liquid and vapor phases. 

Adsorption of compounds from water solution on hydroxylated silica... 

The properties of fullerene molecules arranged in surface layer of fullerene crystals can be characterized from the adsorption of compounds with different functional groups. Although the properties of free fullerene molecules are slightly different from the properties of fullerene in a crystal surface nevertheless the data on adsorption of organic compounds of different classes can be used to characterize intermolecular interaction of fullerenes with organic molecules and properties of fullerene molecules itself. 

On the other hand the heat of adsorption of compound can be presented as sum of the contribution of groups to the heat of adsorption. 

It has been found in many papers (91-97) that the solvent may considerably affect also the relative adsorptivity of substrates. The majority of these authors, however, only point out differences in the relative adsorp-tivities of substrates in competitive hydrogenations under various conditions, or attempt to correlate these adsorptivities with the physical properties of solvents. In order to predict the effect of solvents on the selectivity of heterogeneously catalyzed hydrogenations, it is of course very important to obtain more general information on the effect of solvents on the adsorption coefficients of reacting compounds, based on a qualitative basis. Cerveny, Prochazka, and Ruzicka (70) suggested, for correlation of the effect of solvent on the relative adsorptivity of compounds, an equation in the form... 

For the adsorption of alkyl-substituted aromatics or aliphatic derivatives the configuration of the adsorbed molecule may also be determined as above [via Eq. (10-7)]. It has been established by solvent variation studies (Section 8-1C) that alkyl-substituted aromatics adsorb with the aromatic ring flat and the alkyl group partially attached to the surface, at least from moderately strong solvents. Partial adsorption of compounds of the type X—(CHa)j—Y is also favored in some circumstances. The few examples of this type which have been studied experimentally (27) suggest complete adsorption of the sample molecule, but this is not expected to be true in all cases. 

At low concentrations of solute the relation is approximately linear (X X hC), but the extent of adsorption is limited at high concentration due to the limited number of sites (Fig. 3.4). This isotherm has found use in the smdy of the adsorption of gases on solids however, it is not as useful in defining the adsorption of compounds from solution, particularly onto soils. The heterogeneous nature of a soil would obviously invalidate the first assumption. 

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